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  • 1995-1999  (790)
  • 1985-1989
  • 1930-1934
  • 1920-1924
  • 1810-1819
  • 1997  (790)
  • Inorganic Chemistry  (608)
  • Human  (145)
  • crystal structure  (134)
Datenquelle
Materialart
Erscheinungszeitraum
  • 1995-1999  (790)
  • 1985-1989
  • 1930-1934
  • 1920-1924
  • 1810-1819
Jahr
Schlagwörter
  • 101
    Digitale Medien
    Digitale Medien
    Gravitational inputs modulate visuospatial neglect (1997)
    Springer
    Experimental brain research 117 (1997), S. 341-345 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Key words Unilateral neglect ; Space representation ; Gravitational information ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Right brain-damaged patients with left visuospatial neglect were required to bisect a line placed in front of them in two different body positions (upright and supine) and two different light conditions (light and dark). The neglect patients, unlike right brain-damaged patients without neglect, strongly reduced their rightward directional error in the supine compared with the upright position. No systematic changes were produced by the light-dark manipulation. The present result cannot be explained with an attentional interpretation of hemispatial neglect. We suggest that the present data provide futher evidence that hemineglect is the consequence of a mismatch between different afferent information integrated into an egocentric space representation. According to this model, the presence of a lateralized brain lesion produces asymmetries in some intermediate spatial representations (eye-head, head-trunk, body-environment) but not in the retinotopic one. Any experimental manipulation that reduces the asymmetry of the intermediate representation such as the reduction of gravitational inputs may improve the dynamic integration of the egocentric coordinates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002210050227
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  • 102
    Digitale Medien
    Digitale Medien
    Dynamical systems analysis: a new method of analysing congenital nystagmus waveforms (1997)
    Springer
    Experimental brain research 117 (1997), S. 355-361 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Key words Congenital nystagmus ; Dynamical systems analysis ; Fixed point ; Eigenvalues ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Congenital nystagmus is an oculomotor disorder in which fixation is disrupted by rhythmical, bilateral involuntary oscillations. Clinically these eye movements have been described with some degree of success in terms of their peak-to-peak amplitude, frequency, mean velocity and waveform shape. However, it has not proved possible to diagnose any underlying pathology from the nystagmus characteristics. Here, we propose a new approach to understanding the nystagmus using dynamical systems theory. Our approach is based on the use of delay embedding techniques, which allow one to relate a time series of scalar observations to the state space dynamics of the underlying dynamical system. Using this approach we quantify the dynamics of the nystagmus in the region of foveation and present evidence to suggest that it is low-dimensional and deterministic. Our results put new constraints on acceptable models of nystagmus and suggest a way to make a closer link between data analysis and model development. This approach raises the hope that techniques originally developed to stabilise chaotic systems, by using small perturbations, may prove useful in the control of nystagmus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002210050229
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  • 103
    Digitale Medien
    Digitale Medien
    Kinesthetic perceptions of intrinsic anterior-posterior axes (1997)
    Springer
    Experimental brain research 117 (1997), S. 465-471 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Key words Coordinate system ; Upper limb ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  The purpose of this research was to investigate whether kinesthetic and proprioceptive perceptions of “straight ahead” were defined by a head- or trunk-fixed axis. Subjects were instructed to align the forearm with the head or trunk anterior-posterior (a/p) axis by elbow flexion or extension in the horizontal plane in five different conditions. In each condition the experimenter varied initial elbow and shoulder horizontal flexion or extension angles and head and/or trunk orientation (by rotation about a vertical axis) on each trial before the subject moved the forearm to align it with the head or trunk axis. The upper limb motion was voluntarily constrained to the horizontal plane through the shoulder. Variable errors were significantly lower when subjects aligned the forearm to the trunk-fixed a/p axis. Furthermore, the perceptual errors showed a greater dependence on body segment orientations when the forearm was aligned to the head axis than to the trunk axis. We conclude that the trunk a/p axis is preferred to the head a/p axis for specifying upper limb segment orientations in the horizontal plane at the kinesthetic perceptual level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002210050242
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  • 104
    Digitale Medien
    Digitale Medien
    Effect of contraction strength on responses in biceps brachii and adductor pollicis to transcranial magnetic stimulation (1997)
    Springer
    Experimental brain research 117 (1997), S. 472-478 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Key words Transcranial magnetic stimulation ; Motor cortex ; Motor-evoked potentials ; Silent period ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  The sizes of the motor-evoked potentials (MEPs) and the durations of the silent periods after transcranial magnetic stimulation were examined in biceps brachii, brachioradialis and adductor pollicis in human subjects. Stimuli of a wide range of intensities were given during voluntary contractions producing 0–75% of maximal force (maximal voluntary contraction, MVC). In adductor pollicis, MEPs increased in size with stimulus intensity and with weak voluntary contractions (5% MVC), but did not grow larger with stronger contractions. In the elbow flexors, MEPs grew little with stimulus intensity, but increased in size with contractions of up to 50% of maximal. In contrast, the duration of the silent period showed similar changes in the three muscles. In each muscle it increased with stimulus intensity but was unaffected by changes in contraction strength. Comparison of the responses evoked in biceps brachii by focal stimulation over the contralateral motor cortex with those evoked by stimulation with a round magnetic coil over the vertex suggests an excitatory contribution from the ipsilateral cortex during strong voluntary contractions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002210050243
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  • 105
    Digitale Medien
    Digitale Medien
    Human herpes virus 6 and human herpes virus 8 DNA sequences in brains of multiple sclerosis patients, normal adults and children (1997)
    Springer
    Journal of neurology 244 (1997), S. 450-454 
    Details
    ISSN: 1432-1459
    Schlagwort(e): Key words Multiple sclerosis ; Human herpesvirus 6 ; Human ; herpesvirus 8 ; Polymerase chain ; reaction ; Brain DNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In order to determine whether the newly discovered human herpesviruses (HHVs) are involved in multiple sclerosis (MS), we investigated by polymerase chain reaction the presence of specific deoxyribonucleic acid (DNA) sequences belonging to human herpesvirus 6 (HHV-6) and to human herpesvirus 8 (HHV-8), in the peripheral blood mononuclear cells (PBMCs), and in the brain and spinal cord plaques from MS patients. Normal adult and stillborn children’s brains were investigated as controls. PBMCs from 56 MS patients contained HHV-6 DNA in only 3 cases and in none were there HHV-8 sequences. The cerebral DNA from 5 MS patients was positive for HHV-8 and not for HHV-6 sequences, while the nervous tissue of one patient who died with neuromyelitis optica was positive for HHV-6 and negative for HHV-8. The brains of 4/8 adult controls were positive for HHV-6, as were 3/8 for HHV-8; none of the 7 stillborn children’s cerebral tissue contained HHV-6 sequences, while 2 contained HHV-8 DNA. Although these data do not support a hypothesis that there is a role for these two HHVs in the pathogenesis of MS, nevertheless it may be suggested that (1) the two viruses possess strong neurotropism and the central nervous system seems to be a reservoir for them (2) HHV-6 infection is probably not transmitted maternally, but is acquired later in infancy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004150050121
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  • 106
    Digitale Medien
    Digitale Medien
    Multifocal motor neuropathy (1997)
    Springer
    Journal of neurology 244 (1997), S. 143-152 
    Details
    ISSN: 1432-1459
    Schlagwort(e): Key words Multifocal motor ; neuropathy ; Conduction block ; Anti-GM1 antibodies ; Cyclophosphamide ; Human ; immunoglobulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We present a review of the literature on multifocal motor neuropathy (MMN), a rare neurological disorder which has features in common with both chronic inflammatory demyelinating neuropathy and lower motor neuron disease. Clinically, MMN is characterised by slowly progressive asymmetrical limb weakness, usually most prominent in the forearms. Weakness may be associated with muscle wasting, fasciculations and decreased tendon reflexes. Serum anti-GM1 ganglioside antibody titres may be increased. The diagnostic hallmark of MMN is the electrophysiological demonstration of persistent localised motor conduction blocks, with otherwise normal or near-normal motor and sensory conduction velocities. The pathogenesis of MMN has not been elucidated completely. There is, however, substantial evidence for an autoimmune mechanism. Based on the possible involvement of the immune system in the pathogenesis of MMN the therapeutic efficacy of several immunomodulatory drugs has been tested. Treatment of MMN patients with human immunoglobulin or cyclophosphamide is usually followed by a marked improvement of strength. The finding that MMN is a potentially treatable disorder underscores the importance of distinguishing MMN from lower motor neuron disease, for which no effective therapy is currently available.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004150050065
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  • 107
    Digitale Medien
    Digitale Medien
    Binge cocaine self-administration in humans: intravenous cocaine (1997)
    Springer
    Psychopharmacology 132 (1997), S. 375-381 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Cocaine ; Human ; Intravenous ; Self-administration ; Binge ; Cardiovascular effects ; Subjective effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Cocaine is frequently used in intermittent cycles of repeated dosing, or “binges.” This pattern of cocaine use has been difficult to study in humans because currently available laboratory models use only one daily session during which a single dose or multiple doses are administered. In the present study, seven adult male IV cocaine users completed a protocol investigating changes in cardiovascular and subjective responses during the repeated self-administration of cocaine. Volunteers participated in a 2-day and a 3-day access condition. On each day of access, they participated in two 2.5-h sessions, one at 1200 and another at 1600 hours. In the 2- and 3-day conditions, participants had access to cocaine on 2 or 3 consecutive days, respectively. During sessions, participants could self-administer up to six doses of IV cocaine (32 mg/70 kg) every 14 min. Participants chose not to self-administer cocaine on only 10% of the 420 trials. Acute tolerance developed to the cardiovascular and several subjective effects of cocaine. Heart rate was the only measure that tended to decrease across days of repeated cocaine self-administration. Ratings of “I want cocaine” decreased at the end of the last self-administration session during both 2- and 3-day conditions. There was no difference between the 2- and 3-day conditions for any measure. The laboratory model of “binge” cocaine use established in this study can be used to describe changes in cardiovascular and subjective effects of cocaine within and between bouts of repeated cocaine use.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050358
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  • 108
    Digitale Medien
    Digitale Medien
    Human cytochromes mediating N-demethylation of fluoxetine in vitro (1997)
    Springer
    Psychopharmacology 132 (1997), S. 402-407 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Fluoxetine ; N-Demethylation ; Cytochromes ; Microsomes ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Biotransformation of the selective serotonin reuptake inhibitor antidepressant, fluoxetine, to its principal metabolite, norfluoxetine, was evaluated in human liver microsomes and in microsomes from transfected cell lines expressing pure human cytochromes. In human liver microsomes, formation of norfluoxetine from R,S-fluoxetine was consistent with Michaelis-Menten kinetics (mean Km = 33 μM), with evidence of substrate inhibition at high substrate concentrations in a number of cases. The reaction was minimally inhibited by coincubation with chemical probes inhibitory for P450-2D6 (quinidine), -1A2 (furafylline, α-naphthoflavone), and -2E1 (diethyldithiocarbamate). Substantial inhibition was produced by coincubation with sulfaphenazole (Ki = 2.8 μM), an inhibitory probe for P450-2C9, and by ketoconazole (Ki = 2.5 μM) and fluvoxamine (Ki = 5.2 μM). However, ketoconazole, relatively specific for P450-3A isoforms only at low concentrations, reduced norfluoxetine formation by only 20% at 1 μM, and triacetyloleandomycin (≥ 5 μM) reduced the velocity by only 20–25%. Microsomes from cDNA-transfected human lymphoblastoid cells containing human P450-2C9 produced substantial quantities of norfluoxetine when incubated with 100 μM fluoxetine. Smaller amounts of product were produced by P450-2C19 and -2D6, but no product was produced by P450-1A2, -2E1, or 3A4. Cytochrome P450-2C9 appears to be the principal human cytochrome mediating fluoxetine N-demethylation. P450-2C19 and -3A may make a further small contribution, but P450-2D6 is unlikely to make an important contribution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050362
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  • 109
    Digitale Medien
    Digitale Medien
    Thermal latent coordination compounds (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 569-586 
    Details
    ISSN: 1572-8943
    Schlagwort(e): crystal structure ; metal(II) picolinate and quinaldinate ; thermal degradation of imidazole and pyrazole complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Complexes of the type M(Pa)2(HAz)2 and M(QA)2(HAz)2 (M=cobalt(II) and nickel(II); HPa=picolinic acid, HQa=quinaldic acid; HAz=azoles like imidazole (Him), pyrazole (HPz), benzimidazole (HBzIm) etc.) show a similar thermal behaviour. In the first step of decomposition the corresponding azolinium picolinates or quinaldinates (H2AzPa, H2AzQa) are split off with formation of polymeric mixed ligand complexes M(Pa)(Az) or M(Qa)(Az). X-ray analysis of Co(Qa)2(HBzIm)2 XIIIa illustrates a proton transfer and a subsequent thermal removal of benzimidazolinium quinaldinate (H2BzImQa): Hydrogen bridges from pyrrole nitrogen of the benzimidazole to the non-coordinated oxygen of the quinaldinate predetermine the thermal initiated proton transfer. The high volatility of the heterocyclic acids and the nitrogen coordination are responsible for the formation of the mixed ligand complex Co(Qa)(BzIm) XIVa. Exceptions are the complexes M(Pa)2(HPz)2 XIa-b and M(Qa)2(HIm)2 XVIIa-b. Pyrazole is eliminated from the complexes XIa-b with formation of the solvent-free inner complex M(Pa)2 XIIa-b. From compounds XVIIIa-b quinaldic acid or their decomposition products are split off and a high temperature modification of M(Im)2 XVIIIa-b is formed at elevated temperature. XVIIIa-b are decomposed to the cyanides M(CN)2 similarly to the thermal behaviour of Cu(Im). In the first step the thermal degradation of imidazole and pyrazole adducts of copper(II) picolinates and quinaldinates is characterized by the elimination of azoles. The reason for this thermal behaviour is the weaker coordination of the azole heterocycles in copper chelate compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979029
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  • 110
    Digitale Medien
    Digitale Medien
    Structures and tautomeric interconversions of anthraquinone imine derivatives (1997)
    Springer
    Structural chemistry 8 (1997), S. 197-204 
    Details
    ISSN: 1572-9001
    Schlagwort(e): Tautomerism ; anthraquinone ; crystal structure ; semiempirical computations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Substituted 1-hydroxy-9,10-anthraquinone-9-imines have been found to exhibit tautomeric interconversions between the 9,10- and 1,10-quinonoid forms in the solid state as well as in solution. Single-crystal X-ray crystallography was used to study the structures of 4-(N-acetyl-p-tolylamino)-9-amino-1,10-anthracenedione and 4-hydroxy-1-phenylamino-10-mesitylimino-9(10H)-anthracenone at ambient and low temperatures. The former compound gave crystals belonging to the monoclinic space group P2l/c and, at 295 K,a=9.684(2),b=16.371(3),c=12.097(2) å,Β=110.41(1)
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02263507
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  • 111
    Digitale Medien
    Digitale Medien
    Synthesis and structure of 5-methoxy-4-methylbenzopsoralen (1997)
    Springer
    Structural chemistry 8 (1997), S. 453-457 
    Details
    ISSN: 1572-9001
    Schlagwort(e): Benzopsoralen ; photochemotherapeutic agent ; crystal structure ; molecular mechanics ; AM1 theoretical calculations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 5-Methoxy-4-methyl-2H-benzofuro[3,2-g]benzo-1-pyran-2-one was synthesized and its crystal structure was determined and compared with the optimal conformation arrived at by MM and AM1 theoretical calculations. The latter indicated that the tetracyclic skeleton is planar with total length (C2–C8) 9.23 å, and that the line joining the conters of the terminal-benzene and furan rings makes an angle of 30.5
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02311704
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  • 112
    Digitale Medien
    Digitale Medien
    Modulating effects of a cold water stimulus on opioid effects in volunteers (1997)
    Springer
    Psychopharmacology 131 (1997), S. 313-320 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Morphine ; Butorphanol ; Subjective ; Opiate ; Psychomotor ; Opioid ; Analgesia ; Pain ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The purpose of this study was to characterize the effect of a painful stimulus on morphine and butorphanol effects in healthy non-drug abusing volunteers. Thirteen subjects with no history of opiate dependence participated in a randomized, placebo-controlled, double-blind, crossover trial in which each subject received saline, 2 mg/70 kg butorphanol, and 10 mg/70 kg morphine, IV, in each of two conditions, periodic forearm immersions into either ice-cold water (2°C) or into warm water (37°C). Both opioids reduced self-reported ratings of pain intensity, indicative of analgesia. Several of the subjective effects of morphine were attenuated either during or in between cold-water immersions, including visual analog scale ratings of “coasting (spaced out),”“high (drug “high”),”“sleepy (drowsy, tired),” and “lightheaded”. In contrast, some of butorphanol’s subjective effects were increased by the cold-water manipulation. Morphine impaired psychomotor performance during one of the warm-water immersions, but not during the cold-water immersions. Psychomotor impairment induced by butorphanol was not affected by water temperature. This study provides evidence that opioid effects can be modulated by a painful stimulus in humans.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050298
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  • 113
    Digitale Medien
    Digitale Medien
    Effects of haloperidol and amisulpride on motor and cognitive skill learning in healthy volunteers (1997)
    Springer
    Psychopharmacology 131 (1997), S. 329-338 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Haloperidol ; Amisulpride ; Human ; Cognitive ; Motor ; Skill learning ; Memory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effects of a typical neuroleptic, haloperidol (1 and 2 mg orally), of an atypical neuroleptic, amisulpride (50 and 100 mg) and of a placebo on motor and cognitive skill learning were assessed in 60 healthy volunteers using repeated testing on the Tower of Toronto puzzle. Subjects were asked to solve three blocks of eight trials and, at distance from drug administration, a fourth block. The puzzle was connected to a computer in order to obtain a precise timing of individual moves. Two components of cognitive skill learning were assessed, the ability to learn to solve the puzzle and the acquisition of a problem-solving routine. Subjective feelings of effort and automatisation of the task were assessed using a questionnaire. Like placebo-treated subjects, neuroleptic-treated subjects were able to acquire a motor skill, to learn to solve the puzzle and to acquire a routine. However, haloperidol 2 mg-treated subjects needed significantly more moves to solve the puzzle in blocks 3 and 4, some of them having routinised a non-optimal solution. A significant cognitive slowing was observed in the haloperidol 1mg group in block 4. The performance pattern and verbal reports suggested that haloperidol impaired the higher cognitive functions such as the ability to shift from one strategy to another and/or to assess one’s performance accurately, possibly leading to the development of compensatory strategies. The only deleterious amisulpride effect was a cognitive slowing in block 4, which was observed in the lower dose group.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050300
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  • 114
    Digitale Medien
    Digitale Medien
    A PET-study of [11C]FLB 457 binding to extrastriatal D2-dopamine receptors in healthy subjects and antipsychotic drug-treated patients (1997)
    Springer
    Psychopharmacology 133 (1997), S. 396-404 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words [11C]FLB 457 ; D2-dopamine receptors ; Human ; Positron emission tomography ; Neuroleptic drug
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We recently developed [11C]FLB 457 a substituted benzamide with the very high affinity of 20 pM for D2-dopamine receptors in vitro. The aim of the present exploratory study was to examine the anatomical distribution of [11C]FLB 457 binding in the human brain and to determine extrastriatal D2-receptor occupancy in antipsychotic drug-treated patients. [11C]raclopride was used to obtain reference values for D2-dopamine receptor occupancy in the putamen. After IV injection of [11C]FLB 457 there was a high concentration of radioactivity, not only in the caudate putamen but also in the thalamus and the temporal cortex. The concentration of radioactivity in the frontal cortex, the substantia nigra and the colliculi was slightly higher than in the cerebellum. Pretreatment with haloperidol and fluphenazine indicated that [11C]FLB 457 binding in extrastriatal regions to a high degree represents specific binding to D2-dopamine receptors. The D2-occupancy in antipsychotic drug-treated patients was on the same level in the thalamus and the temporal cortex as that determined with [11C]raclopride in the putamen. The study shows that [11C]FLB 457 has potential for quantitative PET-examination of D2-dopamine receptors in man.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050420
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  • 115
    Digitale Medien
    Digitale Medien
    The effects of food deprivation and incentive motivation on blood glucose levels and cognitive function (1997)
    Springer
    Psychopharmacology 134 (1997), S. 88-94 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Food deprivation ; Blood glucose ; Cognitive function ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The current study investigated the relationships between blood glucose levels, mild food deprivation, sympathetic arousal, and cognitive processing efficiency. Subjects (n = 82) were randomly assigned to four experimental conditions, comprising combined manipulations of food deprivation and incentive motivation. Baseline and mid-session measurements of blood glucose, blood pressure and pulse rate were taken. Subjects completed a number of measures of cognitive processing efficiency and self report measures of affective and somatic state. Although glucose levels were lowered following food deprivation, there was no significant detrimental effect of food deprivation on task performance. However, improved recognition memory processing times were associated with deprivation. Incentive motivation was associated with faster simple reaction times and higher diastolic blood pressure. There were no significant relationships between glucose levels and task performance, further supporting the hypothesis that the brain is relatively invulnerable to short food deprivation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050429
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  • 116
    Digitale Medien
    Digitale Medien
    Age-related differences in the temporal and spatial regulation of matrix metalloproteinases (MMPs) in normal skin and acute cutaneous wounds of healthy humans (1997)
    Springer
    Cell & tissue research 290 (1997), S. 581-591 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Ageing ; Skin ; Proteinase ; Wound ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Despite the association of increasing age with chronic wound-healing disorders and an impaired rate of healing of acute cutaneous wounds, the role of matrix metalloproteinases (MMPs) is unknown. To determine the spatial and temporal patterns and activities of MMP-1, -2, -3 and -9, 132 healthy humans aged between 19 and 96 years underwent 4-mm punch biopsies followed by wound excision between day 1 and day 180 post-wounding. Wounds showed an age-related increase in MMP-2 and MMP-9 immunostaining from day 3; this was associated with degradation of gelatin as shown by zymograms and with increased proteinase activity as shown by azocoll assays. Distinct spatial localisations for each MMP were observed: MMP-2 was found in epidermal structures; MMP-9 was observed in inflammatory cells up to day 21; MMP-1 was localised to keratinocytes at the wound margin. Normal old skin showed pro-MMP-2 bands on zymography and increased MMP-2 immunostaining. These results indicate that: (1) intrinsic ageing is associated with the up-regulation of MMPs previously associated with chronic wound healing; (2) wound-tissue proteinases are essentially active up to day 21 postwounding; and (3) intrinsic ageing may predispose to tissue breakdown disorders because of MMP-2 up-regulation in normal skin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050963
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  • 117
    Digitale Medien
    Digitale Medien
    The fibroblast-specific MAb AS02: a novel tool for detection and elimination of human fibroblasts (1997)
    Springer
    Cell & tissue research 290 (1997), S. 593-599 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Fibroblast-specific antibody ; Fibroblast separation and elimination ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The unwelcome presence of fibroblasts in many cell cultures prevents the long term cultivation of various cell types and work with pure populations. Recently, we described a novel fibroblast-specific monoclonal antibody (MAb AS02) that recognises a membrane-bound antigen. We have now developed a method using the fibroblast-specific MAb AS02 immobilised on goat-anti-mouse-magnetic beads to separate contaminating fibroblasts. An endothelial cell line experimentally contaminated with 5%–50% fibroblasts was successfully purified. Additionally, an endothelial cell line with an initial fibroblast contamination of 1.5% was prepared. A proportion of each preparation was cultured with no separation step being performed, whereas the remainder was cultured after purification with MAb AS02 to exclude the presence of a minor number of fibroblasts (〈0.1%). The proportion of fibroblasts increased up to 38% in the fifth passage of culture without elimination of the low initial fibroblast contamination, whereas in the fraction with the separation step, no fibroblasts were detectable by flow cytometry, even after the fifth passage. We also used the antibody to detect the presence of naturally contaminating fibroblasts in thyrocyte cultures. After cultivation of thyrocyte cultures over five passages, the number of fibroblasts increased dramatically up to 50%–80% of the whole population. Subsequently, we successfully applied the method for complete elimination of naturally contaminating fibroblasts from freshly isolated thyrocyte cultures from enzymatically digested thyroid glands. Thus, MAb AS02 is a fibroblast-specific marker that is a useful tool for the detection and elimination of contaminating fibroblasts. The specificity of MAb AS02 permits the universal application of this antibody for human cell cultures of interest.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050964
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  • 118
    Digitale Medien
    Digitale Medien
    Light-microscopical investigation of the distribution of extracellular matrix molecules and calcifications in human dental pulps of various ages (1997)
    Springer
    Cell & tissue research 289 (1997), S. 145-154 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Teeth ; Dental pulp ; Immunohistology ; Extracellular matrix ; Collagen ; Aging ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The distribution of extracellular matrix molecules, especially collagen types I, III, V, and VI, in the extracellular matrix of the connective tissue of human dental pulp of various ages was studied by polarization and indirect immunofluorescence microscopy by using a conventional fluorescence microscope and a confocal laser scanning microscope. Polarization and immunofluorescence microscopy of paraffin sections showed thick fibers of collagen type I, which represented the main component of the connective tissue matrix of the dental pulp. By indirect immunofluorescence, thin fibers and small bundles of collagen type III were determined to be one of the main fibrillar elements present in the dental pulp matrix. Collagen type IV was detected by a clear intense staining of the basement membrane of blood vessels at all ages examined. Collagens type V and VI formed a dense meshwork of thin microfibrils throughout the stroma of the connective tissue of the dental pulp. These fibers were localized around blood vessels and appeared to be enriched in the subodontoblastic layer. Investigations by means of confocal laser scanning microscopy revealed fibers of collagen type VI spiralling between fully differentiated odontoblasts toward the predentin layer. With advancing age, the connective tissue matrix appeared to be condensed and aggregates of thick fiber bundles could be observed. Furthermore, the participation of various collagen types in the composition of pulp stones was shown. These calcifications and diffuse calcifications increased in frequency with advancing age in a statistically significant manner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050860
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  • 119
    Digitale Medien
    Digitale Medien
    Immunohistochemical localization of the small proteoglycans decorin and biglycan in human intervertebral discs (1997)
    Springer
    Cell & tissue research 289 (1997), S. 185-190 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Small proteoglycans ; Intervertebral disc ; Decorin ; Biglycan ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Immunohistochemistry was used to study the presence and distribution of the core proteins of the small proteoglycans decorin and biglycan in the various compartments of human intervertebral discs. Both proteoglycans could be found in the outer tendon-like parts of the annulus fibrosus, indicating their potential role in collagen network formation and biomechanical stress resistance. The loss of both proteoglycans in the annulus of individuals older than 50 years reflects a normal age-related change. In the nucleus pulposus, decorin could be found in fibrillar areas of the interterritorial matrix, thereby indicating co-localization of decorin with fibrils containing type II collagen. Biglycan was present in the extracellular matrix of the nucleus pulposus of adults. The pericellular immunoreactive rims observed around nucleus pulposus cells and giant chondrones indicated local biosynthetic activity for these small proteoglycans. The staining patterns in cartilage endplates resembled those found in human hyaline articular cartilage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050864
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  • 120
    Digitale Medien
    Digitale Medien
    Differential distribution of five members of the matrix metalloproteinase family and one inhibitor (TIMP-1) in human liver and skin (1997)
    Springer
    Cell & tissue research 289 (1997), S. 173-183 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Collagen ; Matrilysin (PUMP) ; Wound healing ; Tumors ; Fat-storing cells ; Peripheral nerve glial cells ; Fibrocytes ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Matrix metalloproteinases represent a family of zinc-dependent proteolytic enzymes thought to be involved in normal and disease-related tissue remodeling processes. Increasing information about these enzymes is becoming available concerning their primary sequences, regulation at the mRNA level, activation of proenzymes, and modulation of enzyme activity by tissue inhibitors. In contrast, their morphological distribution and biological functions in normal tissues are poorly understood. In the present report, the comparative distribution of five members (gelatinase-A, gelatinase-B, matrilysin, stromelysin-1, and stromelysin-3) of the matrix metalloproteinase family and of one inhibitor (TIMP-1) has been morphologically analyzed in human liver and skin with the aid of new monospecific antibodies. Because of their common designation as matrix proteinases, these enzymes might have been expected to be distributed throughout these tissues, or at least in the connective tissue. However, each member of the family produces a highly specific pattern, staining structures such as arteriolar smooth muscle cells, myoepithelial cells in secretory portions or the luminal lining in excretory ducts of dermal sweat glands, liver bile canaliculi, or structures surrounding peripheral nerve axons. No reactivity is detected in rat tissues.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050863
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  • 121
    Digitale Medien
    Digitale Medien
    GDNF improves survival and reduces apoptosis in human embryonic dopaminergic neurons in vitro (1997)
    Springer
    Cell & tissue research 289 (1997), S. 207-210 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Parkinson’s disease ; Programmed cell death ; Dopamine ; Growth factors ; Neurotransplantation ; Glia ; Human ; Bonnet monkey ; Macaca radiata (Primates)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Dopamine cell death is the primary problem limiting the value of neurotransplantation in human patients with Parkinson’s disease. To address this problem, we added glial cell line-derived neurotrophic factor (GDNF) to cultures of embryonic dopaminergic neurons obtained from human and from Bonnet monkey (Macaca radiata) in an effort to reduce apoptotic cell death and improve overall cell survival. Tissue from three human embryos, 7–8 weeks post-conception, and one 9-week post-conception monkey embryo were dissociated and cultured in F-12 media with 5% human placental serum. GDNF (10 ng/ml) in human cultures nearly doubled dopamine neuron survival and reduced the rate of apoptosis from 6% to 3%. In monkey cultures, GDNF also enhanced dopamine neuron survival and reduced the apoptotic rate. We conclude that GDNF improves the survival of primate embryonic dopamine neurons in culture by reducing apoptosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050867
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  • 122
    Digitale Medien
    Digitale Medien
    Coordinated change between complement C1s production and chondrocyte differentiation in vitro (1997)
    Springer
    Cell & tissue research 289 (1997), S. 299-305 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Complement C1s ; Sandwich ELISA ; Chondrocytes ; Cell culture ; Differentiation ; Ascorbic acid ; Syrian hamster ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. In vitro synthesis of the first component of complement C1s was examined by using hamster epiphyseal chondrocytes (HAC) and human chondrosarcoma cell line HCS-2/8. Hamster and human C1s produced by the cells were quantified by immunoblotting and sandwich enzyme-linked immunosorbent assay (ELISA), respectively. It was possible to measure active and inactive C1s by sandwich ELISA, when we used anti-human C1s monoclonal antibodies, M241 recognizing only active C1s, and M365 and M81 recognizing both active and inactive C1s. Approximately 40% of C1s secreted from HCS-2/8 was found to be activated in the culture medium, whereas C1s from HAC was not. C1s production increased in accordance with chondrocyte differentiation induced by ascorbic acid. In contrast, transforming growth factor-beta1 and basic fibroblast growth factor, which inhibited differentiation, suppressed C1s production. These results confirmed our previous observation showing that C1s synthesis increased with differentiation into hypertrophic chondrocytes in vivo.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050876
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  • 123
    Digitale Medien
    Digitale Medien
    Development of striated rootlets during ciliogenesis in the human oviduct epithelium (1997)
    Springer
    Cell & tissue research 290 (1997), S. 39-42 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Ciliogenesis ; Striated rootlets ; Oviduct ; Ciliated cells ; Ultrastructure ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Striated rootlets in ciliated cells are conical banded structures composed of longitudinally aligned filaments. The formation of striated rootlets during ciliognesis in the human oviduct epithelium was studied by electron microscopy. Primitive rootlets appeared at the proximal side of basal bodies before or at the same time as ciliary budding. After the formation of several striations, the tip of the rootlets extended deeply toward the interior of the cell and became differentiated into two distinct parts, viz., the proximal conical part connected to the basal body and the distal fibrillar part. The periodicity of the striations in the fibrillar part was 68.5±2.95 nm, about 5 nm longer than that of the conical part (63.9±2.25 nm). The dark band in the striation was thicker in the fibrillar part than in the conical part. Since the fibrillar part was not observed in the mature cilium, this part was considered as being either degraded or changed into the conical part during ciliogenesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050905
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  • 124
    Digitale Medien
    Digitale Medien
    Platelet/endothelial cell adhesion molecule-1 (PECAM-1) is localized over the entire plasma membrane of endothelial cells (1997)
    Springer
    Cell & tissue research 290 (1997), S. 623-631 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: PECAM-1 (platelet/endothelial cell adhesion molecule-1) ; Endothelium ; HUVEC (human umbilical vein endothelial cells) ; Myocardium ; Ultrastructure ; Human ; Rabbit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The subcellular localization of PECAM-1 in endothelial cells was examined by using advanced morphological techniques, such as confocal scanning microscopy and immunolabeling procedures for electron microscopy. The localization of PECAM-1 was studied immunohistochemically with five specific monoclonal antibodies and one polyclonal antibody (all anti-human) in human and rabbit myocardium and in isolated endothelial cells. In vivo, PECAM-1 was localized uniformly on the plasma membrane of all vascular endothelial cells, predominantly on the luminal side of vessels. No specific increase in labeling was found at sites of cell-to-cell contact. In vitro, primary isolated cells (human umbilical vein endothelial cells) showed continuous labeling of the entire cell membrane. Cells of higher passages were labeled in a manner similar to freshly isolated cells. Our findings refute the commonly accepted hypothesis that PECAM-1 is localized only at cell-to-cell contacts. Further, we have not been able to confirm the hypothesis regarding the important mechanical role of PECAM-1 in stabilizing the endothelial monolayer. Since PECAM-1 is also expressed on platelets and is known to bind to itself, the way in which PECAM-1-positive endothelial cells are protected against binding of PECAM-1-positive platelets remains unclear. In view of these findings, the role of PECAM-1 in the leukocyte migration cascade needs to be re-evaluated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050968
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  • 125
    Digitale Medien
    Digitale Medien
    Immuno-electron microscopy reveals that the excitotoxin quinolinate is associated with the plasma membrane in human peripheral blood monocytes/macrophages (1997)
    Springer
    Cell & tissue research 290 (1997), S. 633-639 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Quinolinic acid ; Interferon-γ ; Kynurenine ; Electron microscopy ; Immunocytochemistry ; Excitotoxicity ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract.  Quinolinate (QUIN), a tryptophan-derived excitotoxin, was localized ultrastructurally in human peripheral blood monocytes/macrophages (MØ) by immuno-electron microscopy. A combined carbodiimide/glutaraldehyde/paraformaldehyde-based fixation procedure was developed for optimal retention of QUIN in the cell as well as minimal loss of ultrastructure; a silver-enhanced colloidal gold detection system was used for electron-microscopic analysis. Gold particles representing QUIN immunoreactivity were associated with the inner side of the plasma membrane in normal MØ. The number of gold particles increased significantly when QUIN levels were elevated by treatment with its precursor kynurenine, but location of the gold particles remained essentially the same under this condition. Treatment with interferon-γ increased the number of Golgi bodies, vacuoles and pseudopodia, reflecting the activated state of the cell. Significantly increased numbers of gold particles representing QUIN were detectable in approximately the same location as in the case of kynurenine treatment. Combined treatment with kynurenine and interferon-γ maximally increased the number of gold particles at the periphery of the cell. The pseudopodia were intensely stained with gold particles, while they were not detectable in the inner part of the cytoplasm or in any other organelle even under this activated condition. The significance of the specific location of QUIN revealed in the present study and its relation to the release and subsequent actions of QUIN are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050969
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  • 126
    Digitale Medien
    Digitale Medien
    Immunohistochemistry of matrix metalloproteinases (MMP), their substrates, and their inhibitors (TIMP) during trophoblast invasion in the human placenta (1997)
    Springer
    Cell & tissue research 291 (1997), S. 133-148 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words Placenta ; Extravillous trophoblast ; Matrix-type fibrinoid ; Extracellular matrix ; MMP ; TIMP ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract  The invasion of extravillous trophoblast cells into the maternal endometrium is one of the key events in human placentation. The ability of these cells to infiltrate the uterine wall and to anchor the placenta to it as well as their ability to infiltrate and to adjust utero-placental vessels to pregnancy depends, among other things, on their ability to secrete enzymes that degrade the extracellular matrix. Most of the latter enzymes belong to the family of matrix metalloproteinases. Their activity is regulated by the tissue inhibitors of matrix metalloproteinases. We have studied the distribution patterns of matrix metalloproteinases-1, -2, -3, and -9 and their inhibitors TIMP-1 and TIMP-2 as compared to the distribution of their substrates along the invasive pathway of extravillous trophoblast of 1st, 2nd, and 3rd trimester placentas by means of light microscopy on paraffin and cryostat sections as well as at the ultrastructural level (only 3rd trimester placenta). The comparison of different methods proved to be necessary, since the immunohistochemical distribution patterns of these soluble enzymes are considerably influenced by the pretreatment of tissues. All three methods revealed immunoreactivities of both, proteinases and their inhibitors, not only intracellularly in the extravillous trophoblast but also extracellularly in its surrounding matrix, the distribution patterns depending on the stage of pregnancy and on the degree of differentiation of trophoblast cells along their invasive pathway. Within the extracellular matrix, immunolocalization of matrix metalloproteinases as well as their inhibitors showed a specific relation to certain extracellular matrix molecules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050987
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  • 127
    Digitale Medien
    Digitale Medien
    Distribution and subcellular localization of a lysosome-associated protein in human genital organs (1997)
    Springer
    Cell & tissue research 287 (1997), S. 335-342 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Lysosomal membrane antigen ; Immunohistochemistry ; Biosynthesis ; Prostate-membrane-specific antigen ; Apocrine secretion ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The tissue distribution, preferentially in the human male genital system, and the subcellular localization of the lysosome-associated membrane protein 2 (lamp 2) was studied immunohistochemically using a mouse monoclonal antibody, 2D5. Strong immunoreactivity was present in the tubular system of the kidney, in acinar cells of salivary glands and pancreas, prostate, mammary glands, placenta and in cutaneous sweat glands. Moderate immunoreactivity was observed in cerebral neuronal cells, epidermal cells, testis, epididymis, seminal vesicle and endometrium. Very low immunoreactivity was found in liver. In some of the tissues mentioned, the distribution pattern of immunoreactivity is smooth and homogeneous, while in others it is granular and concentrated in the supra- or perinuclear cytoplasm. The subcellular distribution was studied on ultracryosections and on pre-embedding-processed chopper sections of human prostate. In the latter gland, the protein is not restricted to epithelium, but is also present in stromal cells. Ultrastructurally, the immunoreactivity in secretory cells was localized in electron-translucent vacuoles and granules, including the secretory granules. A close association with cell membranes was not generally the case. Only part of the immunoreactive material was linked to the apical plasma membrane pointing to a biosynthesis independent from an association step with the apical plasma membrane. As shown by immunoelectron microscopy and Western blotting, a high amount of lamp 2 is secreted and is found in so-called prostasomes. The findings indicate that in the human prostate most of the membrane-bound lamp 2 is released from the secretory cells, presumably in an apocrine fashion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050758
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  • 128
    Digitale Medien
    Digitale Medien
    Occurrence of enzymes of free radical metabolism suggests the possible cytotoxic capacity of the transitional epithelium of the human ureter (1997)
    Springer
    Cell & tissue research 287 (1997), S. 351-356 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Urothelium ; Tartrate-resistant acid phosphatase ; Nitric oxide synthase I ; Superoxide dismutase ; Immunocytochemistry ; Free radicals ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Three enzymes, viz., tartrate-resistant acid phosphatase (TRAP), nitric oxide synthase I (NOS-I), and superoxide dismutase (SOD), involved in the production and metabolism of free radicals or radical equivalents, were demonstrated by immunocytochemistry in the urothelium of the ureters of six patients of various ages. Two of these enzymes (TRAP and NOS-I) were colocalized in the most apical and lateral border of the superficial cells of the urothelium. In contrast, SOD showed a patchy or granular distribution within the supranuclear region of these cells. Intra- and subepithelial macrophages exhibited a weak TRAP, but no NOS-I or SOD, immune reaction. On the basis of the immunocytochemical findings, arguments in favor of a cytotoxic function of the superficial cells of the human urothelium are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050760
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  • 129
    Digitale Medien
    Digitale Medien
    Number and size of epineurial blood vessels in normal and diseased human sural nerves (1997)
    Springer
    Cell & tissue research 290 (1997), S. 31-37 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Sural nerve ; Blood vessels ; Angiopathic neuropathy ; Vasculitis ; Peripheral neuropathy ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The number and dimensions of epineurial blood vessels in normal human sural nerves have, thus far, not been determined using systematic, reproducible morphometric methods, although this nerve is most frequently used for diagnostic biopsies. Quantitative changes in epineurial blood vessels appear to be major parameters for identifying angiopathy and angiopathic peripheral neuropathy. Therefore, we examined the epineurial blood-vessel number in relation to the age of the patients and to the number and size of the nerve fascicles in each of 51 human sural nerve biopsies. The data from a control group were compared with pathological cases. We found that the number of epineurial blood vessels (normal mean: 57.7) increased significantly (up to 196) in biopsies where there were signs of angiopathy (P≤0.01) or vasculitis (P≤0.05). The increase in the number of epineurial blood vessels usually resulted from a proliferation of capillaries. The fascicular cross-sectional area did not appear to be related to the number of epineurial blood vessels, although it increased significantly in cases with vasculitis (P≤0.05) or an axonal type of neuropathy (P≤0.05). Thus, this study shows that the number of epineurial blood vessels is a helpful parameter in verifying angiopathy and angiopathic peripheral neuropathy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050904
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  • 130
    Digitale Medien
    Digitale Medien
    A model system for long-term serum-free suspension organ culture of human fetal tissues: experiments on digits and skin from multiple body regions (1997)
    Springer
    Cell & tissue research 290 (1997), S. 51-60 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Serum-free culture medium ; Organ culture ; Fetal digits ; Fetal skin ; Nails ; Hair follicles ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. We have optimized a suspension organ culture (SOC) system previously used to study human fetal skin in vitro. Eleven types of media were used to culture fetal digits and skin samples (ranging from 59–91 days of estimated gestational age) for periods of 3 or 4 weeks. The cultures were supplemented with 0%–10% bovine calf serum and exposed to 5%–45% oxygen atmospheres. Optimal conditions, which were selected based upon the morphologic and histologic properties of the cultured tissues, were: DMEM-F12 medium in a serum-free environment with a 45% oxygen atmosphere. The refined SOC system supports the maintenance and/or continued development of the epidermis and dermis of trunk, back, scalp, and digital skin, developing hair follicles, nails, and glands. Overall, development and differentiation mimicked the in vivo state more closely than that observed when using other in vitro culture systems. The effects of bovine calf serum and oxygen levels are presented, and the potential for manipulating the environment of this system for studying mechanisms of cutaneous development is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050907
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  • 131
    Digitale Medien
    Digitale Medien
    Molecular anatomy of the perivascular sheath in human placental stem villi: the contractile apparatus and its association to the extracellular matrix (1997)
    Springer
    Cell & tissue research 290 (1997), S. 601-607 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Placental stem villi ; Perivascular contractile sheath ; Molecules of adhesion plaques ; Extracellular matrix molecules ; Immunocytochemistry ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. In previous studies, we have shown that smooth muscle cells and myofibroblast subpopulations of the perivascular stem villous sheath of the human placenta contain focal adhesion plaques and talin immunoreactivity. The close association of these cells to elastic and collagen fibres have led to the assumption of a functional myofibroelastic unit within the perivascular stem villous sheath. Interactions between the extracellular matrix and smooth muscle cells depend on a variety of structural protein assemblies. In the present study, we examined, by immunocytochemistry, whether the molecular assembly of extracellular matrix proteins and molecules of focal adhesions, known to be essential for signal transduction in smooth muscle cells, are also found in smooth muscle cells of the perivascular stem villous sheath of the human placenta. Vascular and extravascular smooth muscle cells were immunoreactive for α-actinin, vinculin, paxillin and tensin, the integrin chains α1 and β1, and the basement membrane components laminin and heparan/-chondroitin sulfate proteoglycan perlecan. pp125FAK did not react. In the extracellular matrix of blood vessel walls and the perivascular stem villous sheath, we found immunoreactivity of fibronectin and collagen types I, VI and undulin (collagen type XIV). From our data we conclude that within the perivascular stem villous sheath, there exists a system of signal transduction molecules, indicating a cross talk between the smooth muscle cells of this sheath and their surrounding extracellular matrix.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050965
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  • 132
    Digitale Medien
    Digitale Medien
    Human follicular dendritic cells in vitro and follicular dendritic-cell-like cells (1997)
    Springer
    Cell & tissue research 288 (1997), S. 381-389 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Germinal center ; Follicular dendritic cells ; Cell culture ; Adhesion and co-stimulatory molecules ; Emperipolesis ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Human follicular dendritic cell (FDC)-like cells (FLC) have been utilized for the in vitro analysis of germinal center reactions. However, there is no consensus whether FLC represent FDC in vitro. The purpose of the present study has therefore been to determine distinguishing features of FDC and FLC in vitro. The expression of CD40, CD54, CD49d, cytokine (γ-IFN and IL-4)-dependent MHC-class II, and CD106 was observed to be specific for the determination of FDC in long-term culture. The cytokine-dependent emperipolesis of germinal center B cells was establised as another discriminating property for FDC in vitro. In 2 out of 72 long-term cultures of FDC, we encountered dividing cells among the non-dividing population of FDC. The dividing cells expressed accessory molecules similar to those of FDC but showed emperipolesis only for the initial few days of their growth. FDC did not enhance the CD40-dependent proliferation of germinal center B cells; in contrast, FLC augumented it. Both types of cells produced a significant amount of cytokine-dependent IL-6. Further studies are needed to determine whether FLC originate from FDC in vitro.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050824
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  • 133
    Digitale Medien
    Digitale Medien
    Angioarchitecture of the human spermatic cord (1997)
    Springer
    Cell & tissue research 288 (1997), S. 391-398 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Spermatic cord ; Pampiniform plexus ; Arterio-venous anastomoses ; Casting preparations ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Human spermatic cords were investigated by means of cast preparations, light-microscopic examination and computer-aided 3-dimensional reconstructions from serial sections of paraffin-embedded material. After leaving the testis, the testicular veins formed two principal groups co-existing side by side. Numerous veno-venous anastomoses could be observed within each individual group, whereas only a few mutual intergroup anastomoses were found. The testicular artery ran within one group but showed no close topographical relationship to the other group. Light microscopy of the serial sections revealed that the group of veins with no close topographical relationship to the testicular artery ran at a distance of several centimeters embedded within fatty tissue. With the help of computer-aided 3-dimensional reconstructions, a spatial picture of the vascular organization was obtained. These results allowed the following classification of the veins of the pampiniform plexus. Group-I veins formed a tight plexus around the testicular artery by means of veno-venous anastomoses. Group-II veins formed veno-venous anastomoses between each other and ran over at a sizeable distance embedded in fatty tissue but showed no close topographical relationship to the testicular artery. Group-III vessels formed veno-venous anastomoses between group-I and group-II. Group IV veins formed arterio-venous anastomoses with the testicular artery. Based on the differences in wall structure and diameter, a subclassification in group-I and group-II was undertaken. This organization of the veins of the human pampiniform plexus should further the understanding of physiological processes, such as the transfer of hormones and other substances from the veins to the testicular artery and vice versa. It should also facilitate the tracing of the veins during antegrade sclerosing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050825
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  • 134
    Digitale Medien
    Digitale Medien
    Distribution of heat-shock protein 60 immunoreactivity in testes of infertile men (1997)
    Springer
    Cell & tissue research 288 (1997), S. 539-544 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Testis ; hsp60 ; Infertility ; Spermatogonia ; Immunohistochemistry ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The immunohistochemical localization of heat-shock protein 60 (hsp60) was investigated in testicular biopsies obtained from 121 adult men with disturbed fertility. In normal unaffected tubules, hsp60 immunoreactivity was localized to spermatogonia, primary spermatocytes and Sertoli cells. In spermatogonia, cytosolic and mitochondrial labelling could be differentiated. In general, the number of stained spermatogonia decreased with the loss of spermatogenic function. A significant (P〈0.01) reduction of stained spermatogonia was observed in testes with maturation arrest of spermatogenesis at the level of primary spermatocytes (30.2±21.6%) compared with testes exhibiting normal spermatogenesis. In addition, the decrease in the score correlated significantly with the diminution of cytosolic hsp60 immmunolabelling (coefficient r=0.25, P=0.03). There was a significant difference (P〈0.01) in the percentage of cytosolic-stained spermatogonia in testes with a score equal to or greater than 5 (14.7±9.8%) and a score less than 5 (8.9±6.9%). These observations suggest that a low level of hsp60 expression in spermatogonia may lead to a different pattern of protection, which in turn could be involved in low spermatogenic efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050839
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  • 135
    Digitale Medien
    Digitale Medien
    Complement Cls, a classical enzyme with novel functions at the endochondral ossification center: immunohistochemical staining of activated Cls with a neoantigen-specific antibody (1997)
    Springer
    Cell & tissue research 288 (1997), S. 557-565 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Complement Cls ; Neoantigen ; Cartilage ; Hypertrophic chondrocyte ; Immunohistochemistry ; Rheumatoid arthritis ; Decorin ; Syrian hamster ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The secondary ossification center of 14- to 16-day-old hamster tibiae was examined immunohistochemically with active and inactive Cls-specific antibodies, RK5 and RK4, respectively. At the ossification center, chondrocytes differentiate from proliferating and hypertrophic to degenerating stages, and their site is occupied by the bone marrow. Cls was strongly immunostained in hypertrophic chondrocytes. In order to discover whether Cls is activated at a particular site, the cartilage was immunostained with RK5 and RK4. RK5 mainly reacted with degrading matrix around invading vessels. In contrast, RK4 strongly stained hypertrophic chondrocytes. Immunoelectron microscopy revealed Cls on degrading fragments of chondrocytes and fibers of cartilage matrix. Decorin, one of the major matrix proteoglycans, was dose and time dependently degraded by Cls. Type II collagen and type I gelatin were also degraded. Articular cartilage from patients with rheumatoid arthritis was positively immunostained (11/12 cases) with an anti-Cls monoclonal antibody (mAb) PG11, whereas normal articular cartilage (5/5 cases) was negative, suggesting Cls participation in the etiology of rheumatoid arthritis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050841
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  • 136
    Digitale Medien
    Digitale Medien
    Distribution of neuropeptide-containing nerve fibers in the human submandibular gland, with special reference to the difference between serous and mucous acini (1997)
    Springer
    Cell & tissue research 288 (1997), S. 25-31 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Submandibular gland ; Neuropeptide Y ; Vasoactive intestinal polypeptide ; Galanin ; Substance P ; Calcitonin gene-related peptide ; Immunohistochemistry ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Distribution of neuropeptide Y (NPY)-, vasoactive intestinal polypeptide (VIP)-, galanin (GAL)-, substance P (SP)-, and calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers in the human submandibular gland was examined by the peroxidase-antiperoxidase method with attention to high-quality fixation and the condition of patients. NPY-, VIP-, and GAL-immunoreactive varicose fibers were densely distributed around the acini and ducts. Some of these fibers extended between acinar cells. The density of SP- and CGRP-immunoreactive fibers was relatively low. The number of NPY-, VIP-, and GAL-immunoreactive fibers around the mucous acini was significantly higher than around the serous acini. In the perivasculature, NPY-immunoreactive fibers were more numerous than other immunoreactive fibers. No somatostatin-, leucine-, or methionine-enkephalin-immunoreactive fibers were detected. Our findings suggest that a large number of periacinar VIP-, NPY-, and GAL-immunoreactive fibers may participate in regulating the synthesis of saliva and its secretion. Since the VIP-, NPY-, and GAL-immunoreactive fibers are more numerous around the mucous acini than around the serous ones, these fibers may take part more actively in regulating the secretory mechanisms in the mucous acini than in the serous ones. The relatively low number of CGRP- and SP-immunoreactive fibers suggests that they are less involved in the function of the human submandibular gland. Perivascular peptidergic fibers, especially NPY-immunoreactive fibers, may be involved in controlling local blood flow in this gland.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050789
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  • 137
    Digitale Medien
    Digitale Medien
    Fine structure and distribution of lymphatic vessels in the human dental pulp: a study using an enzyme-histochemical method (1997)
    Springer
    Cell & tissue research 288 (1997), S. 79-85 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Lymphatic vessels ; Blood vessels ; Dental pulp ; 5′-nucleotidase ; Alkaline phosphatase ; Enzyme histochemistry ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The existence of lymphatic vessels in the human dental pulp and their distribution were established by light and electron microscopy using an enzyme-histochemical method. The distinction between lymphatic and blood vessels was made by light microscopy on cryostat sections of undecalcified and decalcified teeth using 5′-nucleotidase(5′-Nase)-alkaline phosphatase double staining. On the tissue surface, 5′-Nase-positive lymphatic vessels were highlighted with good contrast and resolution by backscattered electron imaging using scanning electron microscopy. By transmission electron microscopy, dense granular precipitations resulting from the 5′-Nase reaction were seen on the luminal surface of the lymphatic endothelial cells as well as in the area at the basal side, but were absent in the blood vessels. These lymphatic vessels were more numerous in the central part than in the peripheral odontoblastic layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050794
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  • 138
    Digitale Medien
    Digitale Medien
    Characterization of adult human heart fibroblasts in culture: a comparative study of growth, proliferation and collagen production in human and rabbit cardiac fibroblasts and their response to transforming growth factor-beta1 (1997)
    Springer
    Cell & tissue research 288 (1997), S. 87-93 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Cardiac fibroblasts ; Cell culture ; Growth ; Proliferation ; Collagen production ; Tranforming growth factor-beta1 ; Human ; Rabbit (New Zealand)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Fibroblasts constitute the majority of non-myocyte cells in the heart, but little is known about the biology of human cardiac fibroblasts. We have cultured and characterized fibroblasts from young adult human heart and compared their biological features with those of cells obtained from the ventricular tissue of sex- and developmental-stage-matched rabbits. Cell morphology and growth was determined by light microscopy and by measuring protein synthesis. The proliferative capacity of cells was determined by measuring the doubling time and the level of incorporation of 3H-thymidine into DNA under normal conditions of cell culture and in response to several growth factors. Production of collagen type I was determined at the mRNA level by assessing the steady state level of pro α1 20(l) collagen mRNA in cardiac fibroblasts under normal culture conditions and in response to transforming growth factor-beta (TGF-β), and at the protein level by immuno-slot blot analysis. Ventricular tissue from adult human heart was used successfully for the preparation of passagable (up to nine passages) cultured cardiac fibroblasts. They had a significantly larger surface area per cell than rabbit cells. Under normal culture conditions, they showed a lower rate of DNA synthesis and longer doubling time than rabbit cardiac fibroblasts at the matching passage. The magnitude of growth-factor-induced changes in the incorporation of 3H-thymidine into DNA was lower in human cells than in rabbit cardiac fibroblasts, as was the level of mRNA for pro α1(l) collagen. The TGF-β1-induced increase in pro α1(l) collagen mRNA was modest in human cardiac fibroblasts. Thus, significant differences exist between the biological properties of human and rabbit cardiac fibroblasts in culture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050795
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  • 139
    Digitale Medien
    Digitale Medien
    Insulin-like growth factor-I stimulates in vitro migration of preosteoclasts across bone endothelial cells (1997)
    Springer
    Cell & tissue research 288 (1997), S. 101-110 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Insulin-like growth factor-1 (IGF-I) ; Bone endothelial cells ; Preosteoclasts ; Co-culture ; Cell migration ; Electron microscopy (transmission and scanning) ; Bovine ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Little is known about the factors and the mechanisms involved in preosteoclast emigration from the vasculature. In this study, an in vitro model of bone endothelial lining was mimicked by culturing bone endothelial (BBE) cells at confluence on a 3-μm pore polycarbonate membranes. Preosteoclastic (FLG 29.1) cells were then added on top of the BBE cell monolayer and 10 nM insulin-like growth factor-1 (IGF-I) was added below the supporting membrane. Scanning and transmission electron microscopy were used to evaluate the chemotactic responses of preosteoclastic FLG 29.1 cells towards the IGF-I generated gradient. IGF-I potently stimulated chemotaxis in the FLG 29.1 cells, as shown by the migration of the preosteoclastic cells across the underlying BBE and through the intercellular junctions between adjacent endothelial cells. Subsequently, FLG 29.1 cells penetrated the pores of the supporting membrane and reached the lower face of the membrane. Thus, IGF-I, which is abundantly present in the bone tissue microenvironment, may play a paracrine role in the recruitment of the circulating preosteoclasts from the vascular compartment into the bone tissue. This in vitro model, which mimicks the in vivo phenomenon of preosteoclast extravasation, should prove useful in elucidating the molecular mechanisms that underlie this process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050797
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  • 140
    Digitale Medien
    Digitale Medien
    Human cornea and sclera studied by atomic force microscopy (1997)
    Springer
    Cell & tissue research 288 (1997), S. 111-118 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Cornea ; Sclera ; Collagen ; Extracellular matrix ; Atomic force microscopy ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The purpose of this study was to investigate the ultrastructure of the extracellular matrix of human cornea and sclera by using the atomic force microscope (AFM). Specimens of human cornea (n=16) and sclera (n=10) were obtained from a cornea bank or from enucleated eyes (n=1; clinical and histopathological diagnosis: choroidal melanoma) and fixed in Karnovsky solution. The AFM resolved individual collagen fibrils in corneal and scleral tissue. Scleral collagen fibrils had a diameter ranging from 118.3 to 1268.0 nm and showed clear banding with a mean axial D-periodicity of 77.02 nm. The mean gap depth between the two overlaps was larger in the sclera than in the cornea. The diameter of corneal collagen fibrils ranged from 48.0 to 113.0 nm. In contrast to the sclera, the corneal collagen fibrils did not exhibit clear banding as their surface pattern. Closely attached fibrils with a beaded to globular structure were predominant in the cornea. The mean axial D-periodicity of the corneal collagen fibrils was 68.50 nm. In both tissues, the AFM resolved structures resembling cross-bridges between adjacent fibrils. The corneal collagen fibrils showed fibrillar properties that were different from those of the sclera, and that therefore might be essential for the spatial organization responsible for the optical quality of the cornea.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050798
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  • 141
    Digitale Medien
    Digitale Medien
    Potent inhibition of interleukin-6 expression in a human astrocytoma cell line by tenidap (1997)
    Springer
    Cell & tissue research 288 (1997), S. 251-257 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Interleukin-6 ; Interleukin-1β ; Tenidap ; Astrocytes ; Alzheimer’s disease ; Therapy ; Cell culture ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Tenidap is a structurally novel antirheumatic agent with anti-inflammatory and analgesic properties. Previous studies have shown that tenidap is able to inhibit the production and action of cytokines such as interleukin-1, interleukin-6 (IL-6) and tumour necrosis factor α. However, the mechanisms by which tenidap inhibits cytokine synthesis are not yet known. We investigated in the human astrocytoma cell line U373 whether tenidap inhibits IL-6 synthesis by inhibition of certain signal transduction processes leading to IL-6 synthesis. Cells were stimulated with different substances which have previously been shown to activate protein kinase A or C, reactive oxygen intermediates as well as transcription factors such as nuclear factor kappa B and AP-1 and which all result in IL-6 synthesis. Tenidap was a very potent inhibitor of IL-6 synthesis independent of the stimuli used, suggesting an inhibitory mechanism other than inhibition of a certain signal transduction pathway. Since IL-6 has been shown to be involved in the etiopathology of Alzheimer’s disease and since the use of nonsteroidal anti-inflammatory drugs appears to be of therapeutical benefit, it is concluded that tenidap should be tested in clinical trials in order to determine whether it may be useful for the treatment of Alzheimer’s disease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050810
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  • 142
    Digitale Medien
    Digitale Medien
    E-cadherin and P-cadherin have partially redundant roles in human epidermal stratification (1997)
    Springer
    Cell & tissue research 288 (1997), S. 307-316 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Keratinocyte ; Cadherin ; Stratification ; Epidermal morphogenesis ; Intercellular adhesion ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Classical cadherins are Ca2+-dependent homotypic intercellular adhesion molecules that play major regulatory roles in tissue morphogenesis. Human epidermis, which expresses two classical cadherins (E- and P-cadherins), undergoes continual differentiation and morphogenesis, not just during embryonic development, but throughout life. The relative roles of E- and P-cadherin in epidermal morphogenesis have been studied in human epidermal keratinocytes in culture. In these cultures, tissue morphogenesis can be initiated simply by elevation of the extracellular Ca2+ concentration, which activates the cadherins, initiates desmosome organization, and then induces reorganization of the culture from a monolayer into a multilayered, more differentiated, epithelial-like structure. By examination of cultures after several days in high Ca2+, previous data have shown that concurrent inhibition of both E- and P-cadherins nearly abrogates the Ca2+-induced stratification response; however, it has not been possible to discern from these studies whether the two cadherins have unique or redundant regulatory properties. The present study has demonstrated, via electron-microscopic analysis of cultures at an early stage in stratification, that inhibition of either of the cadherins alone does not affect the initiation of stratification, i.e. the formation of up to 2–3 cell layers. Thus, E-cadherin and P-cadherin may have similar regulatory functions with respect to the initiation of stratification. However, if stratification is to continue further to produce a tissue-like structure of 5–7 cell layers, then E-cadherin is required and P-cadherin cannot act as a substitute, presumably because of the distinct localizations of E- and P-cadherins; E-cadherin is found in all cell layers of the stratified epithelium, whereas P-cadherin is lost after the basal keratinocytes become detached from the basement membrane and assume a suprabasal position. Therefore, basal cells, which have two cadherins, can utilize either cadherin to initiate stratification, whereas superficial cells, which have only E-cadherin, are dependent on this cadherin for further stratification.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050816
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  • 143
    Digitale Medien
    Digitale Medien
    Cytokeratin 17 as an immunohistochemical marker for intramural cytotrophoblast in human first trimester uteroplacental arteries (1997)
    Springer
    Cell & tissue research 288 (1997), S. 335-343 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Uteroplacental artery ; Trophoblast invasion ; Intramural cytotrophoblast ; Cytokeratin 17 ; Placenta ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Trophoblast cells, as blastocyst-wall derivatives, are of epithelial origin and differentiate initially into syncytiotrophoblast and cytotrophoblast subpopulations. Cyto- and syncytiotrophoblasts are the two cell types present in the surface cell layers of placental villi. Cytotrophoblastic cells lie in contact with the basal lamina and are the proliferating stem cells that guarantee cytotrophoblast and syncytiotrophoblast persistence. Implantation and placenta formation are mainly based on these two cell types. Villous cytotrophoblasts are the stem cells for all extravillous trophoblast subpopulations, which exhibit strictly regulated invasiveness. One aspect of extravillous trophoblasts is that they invade maternal endometrial spiral arteries and dilate them in order to achieve sufficient fetal blood supply. During this process, trophoblast cells, which are located in the remodelled uteroplacental artery walls, are thus defined as intramural cytotrophoblasts. Trophoblast differentiation is accompanied and defined by alterations in, for example, the translation pattern for cytokeratin genes. In an immunohistochemical study, we have demonstrated that only intramural cytotrophoblasts, from all the trophoblast populations of the junctional zone, express cytokeratin 17. Furthermore, cell shape and vascular architecture indicate that, in human placenta, intra-arterial trophoblast cells reach their destination by migration through the endometrial interstitium with consecutive intravasation. Cytokeratin 17, in particular, can therefore be used as a specific immunohistochemical marker for the intramural trophoblast subpopulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050819
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  • 144
    Digitale Medien
    Digitale Medien
    A step toward a human-robot cooperative system (1997)
    Springer
    Artificial life and robotics 1 (1997), S. 181-184 
    Details
    ISSN: 1614-7456
    Schlagwort(e): Human ; robot cooperation ; Multimedia interface ; Robot teaching method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract In the near future, we will have to live with many machines such as home robots, hospital robots, and so on. User-friendly communication between humans and those machines is very important for a cooperative system utilizing their features and abilities. As an example of a human-robot cooperative system, we propose an intuitive approach to robot teaching with multimedia tools.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02471137
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  • 145
    Digitale Medien
    Digitale Medien
    Relation of the mental foramen to teeth on the mandibles belonging to the Byzantium period (1997)
    Springer
    International journal of anthropology 12 (1997), S. 1-4 
    Details
    ISSN: 1824-3096
    Schlagwort(e): Human ; Mental foramen ; Byzantium period
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Fifty mandibles belonging to the Byzantium period were studied in order to determine to racial differences about of the localization of the mental foramen according to the mandibular teeth. Mandibles of adult males without missing teeth, proximal decay and proximal attrition were used. On the right side, the most common position of the mental foramen was between the first and second lower teeth (50%), whereas on the left side, the most common position was in line with the longitudinal axis of the lower second premolar tooth (46%). Because of materials including mostly Alpine's and a few of Mediterranean subraces, two different positions of the mental foramen were determined in high similar ratios.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02447884
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  • 146
    Digitale Medien
    Digitale Medien
    Face immersion increases vagal activity as assessed by heart rate variability (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 394-399 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Diving reflex ; Heart rate fluctuation ; Breathing frequency ; Bradycardia ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We examined whether the diving reflex without breath-holding (face immersion alone) increases vagal activity, as determined by heart rate variability. A group of 15 men [mean age 20 (SD 3) years, height 172 (SD 5) cm, body mass 68 (SD 9) kg] performed 12 trials at various breathing frequencies (5, 10, 15, 20, 30 breaths · min−1 and uncontrolled breath) with or without face immersion. The R-R intervals of the ECG and gas exchange variables were recorded during the 2 min of each trial. The subjects immersed their faces in 8–10°C water while breathing through a short snorkel. The subject sat in the same position either with or without face immersion. The mean R-R interval (RRmean), standard deviations (SDRR) and coefficient of variance (CVRR) of the R-R interval were calculated from the R-R intervals during 30–120 s. The face immersion significantly increased SDRR and CVRR (P〈0.05), and increased RRmean (P〈0.05) at 20 breaths · min−1. Face immersion itself had no effect on oxygen uptake, tidal volume, end-tidal O2 and CO2 partial pressures. The diving reflex without breath-holding increased the heart rate variability, indicating that face immersion alone increases vagal activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210050267
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  • 147
    Digitale Medien
    Digitale Medien
    Somatostatin attenuates the hyperthermia induced increase in neutrophil concentration (1997)
    Springer
    European journal of applied physiology 77 (1997), S. 149-156 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Hyperthermia ; Hormones ; Growth hormone ; Immunology ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This study was designed to test the hypothesis that the immune changes seen during in vivo whole body hyperthermia are mediated by elevations in the plasma concentrations of either catecholamines, growth hormone or β-endorphins. Eight healthy volunteers were immersed in a hot water bath (WI; water temperature 39.5°C) for 2 h during which their rectal temperature rose to 39.5°C. In a single blind, randomized, cross-over study the stress hormone effects were blocked one at a time by administration of propranolol, somatostatin or naloxone; the results were compared to those obtained during saline infusion (control). Blood samples were collected before, at the end of 2 h of WI (body temperature 39.5°C), and 2 h later. Hormone blockade did not abolish the hyperthermia-induced recruitment of natural killer (NK) cells to the blood, and no influence was observed on the percentages or concentrations of any other subpopulations of blood mononuclear cells, except that the number of cluster designation (CD)3+ cells slightly increased after hyperthermia only in the propranolol experiment. Furthermore, the NK cell activity, both unstimulated and interferon-α or interleukin-2 stimulated, did not differ from the control situation. It is of interest, however, that somatostatin partly abolished the hyperthermia induced increase in the neutrophil number. Based on these data and previous results showing that growth hormone infusion increases the concentration of neutrophils in the blood, it is suggested that growth hormone is at least partly responsible for hyperthermia induced neutrocytosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210050313
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  • 148
    Digitale Medien
    Digitale Medien
    Positive end expiratory pressure as a method for preventing acute mountain sickness (1997)
    Springer
    European journal of applied physiology 77 (1997), S. 32-36 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Acute mountain sickness ; Human ; Peep ; Prevention ; Hypoxia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In order to study the use of positive end expiratory pressure (PEEP) to prevent acute mountain sickness (AMS), 22 subjects were exposed randomly to 8-h hypobaric hypoxia in a hypobaric chamber (4500 m, 589 hPa, 22°C) once being administered 5-cm H2O PEEP and once without. The prevention of AMS by PEEP was evaluated by scoring AMS according to the Lake Louise system (self-report questionnaire and clinical assessment) throughout the experiment with O2 saturation (SO2) and heart rate measurements being made. Arterial blood analyses (partial pressures of arterial O2 and CO2, P aO2, P aCO2, and pH) were made at the end of the exposure. Results showed decreased AMS scores with PEEP at the end of the 8-h hypoxia [1.50 (SEM 1.32) vs 3.23 (SEM 2.07), P 〈 0.01 for self-report plus clinical assessment scores] with a lower prevalence (23% vs 55%, P 〈 0.01). The SO2, P aO2, P aCO2 and HCO3 − did not change significantly. However, a smaller increase in arterial pH [7.47 (SEM 0.02) vs 7.50 (SEM 0.02), P 〈 0.05] was observed with PEEP, attesting a lesser alkalosis. Moreover, heart rate increased with PEEP (P 〈 0.05). In conclusion, this study would suggest that a 5-cm H2O PEEP may help decrease AMS scores at the end of an 8-h exposure to hypoxia in a hypobaric chamber. Such a method could be used to prevent AMS in such experimental conditions without adverse effects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210050296
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  • 149
    Digitale Medien
    Digitale Medien
    Influence of long-latency reflex modulation on the performance of quick adjustment movements (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 328-334 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Muscle stretch ; Long-latency reflex ; Adjustment movement ; Motor control ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of long-latency reflex modulation on the performance of a quick adjustment movement following a muscle stretch was studied in 26 healthy male subjects. When the subjects felt a sudden angle displacement in the direction of a wrist extension they were required to make an adjustment movement by moving a handlebar, held in the hand, to align with a target position as quickly and as accurately as possible. The index of performance (adjustment time) was the time taken to move the handle to the target position from stretch onset. A DC torque motor was used to evoke electromyographic (EMG) reflex responses on a wrist flexor. Averaging of the rectified EMG, recorded from surface electrodes placed over the flexor, showed short- and long-latency reflexes (M1 and M2 components). For all subjects, the amplitudes of the reflex components decreased during the adjustment movement because the target position for this study was fixed to the extension side of the wrist joint. The decrease in the M2 component, which is considered to be a transcortical reflex, was significantly larger than the decrease in the M1 component, which is spinal reflex. The main finding was of a positive correlation between the length of adjustment time and the degree of reduction of M1 and M2 with the adjustment movement (r = 0.602 for M1, P 〈 0.01; r = 0.850 for M2, P 〈 0.001). Moreover, there were correlations between the consistency of the voluntary response onset and the degree of M2 decrease (r = 0.577, P 〈 0.01), and between the consistency of the voluntary response onset and the length of the adjustment time (r = 0.603, P 〈 0.01). Therefore, we have concluded that the subjects who were able to perform adjustment movements within a short time could modulate the long-latency reflex of the muscle involved in such movements in order to make the function of their voluntary muscle activity more effective, and thus were able to respond appropriately.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210050256
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  • 150
    Digitale Medien
    Digitale Medien
    The crystal and molecular structures of cellulose I and II (1997)
    Springer
    Glycoconjugate journal 14 (1997), S. 677-690 
    Details
    ISSN: 1573-4986
    Schlagwort(e): molecular dynamics ; crystal structure ; cellulose I and II
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The paper describes molecular dynamics (MD) simulations on the crystal structures of the Iβ and II phases of cellulose. Structural proposals for each of these were made in the 1970s on the basis of X-ray diffraction data. However, due to the limited resolution of these data some controversies remained and details on hydrogen bonding could not be directly obtained. In contrast to structure factor amplitudes in X-ray diffraction, energies, as obtained from MD simulations, are very sensitive to the positions of the hydroxyl hydrogen atoms. Therefore the latter technique is very suitable for obtaining such structural details. MD simulations of the Iβ phase clearly shows preference for one of the two possible models in which the chains are packed in a parallel orientation. Only the parallel-down mode (in the definition of Gardner and Blackwell (1974) J Biopolym 13: 1975-2001) presents a stable structure. The hydrogen bonding consists of two intramolecular hydrogen bonds parallel to the glycosidic linkage for both chains, and two intralayer hydrogen bonds. The layers are packed hydrophobically. All hydroxymethyl group are positioned in the tg conformation. For the cellulose II form it was found that, in contrast to what seemed to emerge from the X-ray fibre diffraction data, both independent chains had the gt conformation. This idea already existed because of elastic moduli calculations and 13C-solid state NMR data. Recently, the structure of cellotetraose was determined. There appear to be a striking similarity between the structure obtained from the MD simulations and this cellotetraose structure in terms of packing of the two independent molecules, the hydrogen bonding network and the conformations of the hydroxymethyl group, which were also gt for both molecules. The structure forms a 3D hydrogen bonded network, and the contribution from electrostatics to the packing is more pronounced than in case of the Iβ structure. In contrast to what is expected, in view of the irreversible transition of the cellulose I to II form, the energies of the Iβ form is found to be lower than that of II by 1 kcal mol-1 per cellobiose.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018509231331
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  • 151
    Digitale Medien
    Digitale Medien
    Biomechanik von Femurverriegelungsmarknägeln im Knochen-Implantat-Verbund (1997)
    Springer
    Langenbeck's archives of surgery 382 (1997), S. 167-172 
    Details
    ISSN: 1435-2451
    Schlagwort(e): Key words Biomechanics ; Fracture-fixation-intramedullary ; Femoral fractures-diaphyseal ; Unreamed ; Cadaver study ; Human ; Schlüsselwörter Biomechanik ; Intramedulläre Frakturfixation ; Femorale Diaphysenfraktur ; Unaufge-bohrt ; Studie an menschlichen Leichen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Ziel der Studie war die vergleichende Untersuchung verschiedener Femurverriegelungsnägel auf die Primärstabilität im Knochen-Implantat Verbund (KIV). Dabei wurden die folgenden Implantate in einer Modellosteosynthese getestet: AO-Universal-Femur-nagel (AOU) 11 mm, AO unaufgebohrter Femurnagel Stahl 9 mm, Verriegelung mit 3,2–3,9-mm-Bolzen (SUFN3,9), SUFN 9 mm, mit 4,3–4,9-mm-Bolzen (SUFN4,9), AO unaufgebohrter Femurnagel Titan (12TUFN) 12 mm, mit 4,3–4,9-mm-Bolzen, TUFN 9 mm, Verriegelung mit 4,3–4,9-mm-Bolzen (9TUFN). Die Prüfungen wurden mit einer Universalprüfmaschine an 40 humanen, gepaarten, kältekonservierten Kadaverfemora durchgeführt. Jeder einzelne Knochen wurde zunächst im intakten Zustand geprüft, dann wurde die Osteotomie durchgeführt und das jeweilige Implantat eingesetzt. Ausgewertet wurde die relative Steifigkeit. Es zeigte sich eine signifikant höhere Torsionssteifigkeit der nicht soliden ungeschlitzten Femurnägel im Vergleich zu dem geschlitzten AOU. Die Biegesteifigkeit des KIV des TUFN mit 12 mm Durchmesser war signifikant höher als die Biegesteifigkeit des KIV der anderen Implantate. Bei der axialen Belastung zeigte der KIV des SUFN4,9 eine signifikant höhere Steifigkeit als der KIV des TUFN. Die Steifigkeitsunterschiede zwischen den verschiedenen KIV waren bei der axialen Belastung und Biegebelastung relativ geringer als bei der Torsion. Für die Torsionssteifigkeit ist das Nagelprofil (±Schlitz) entscheidender Parameter. Zwischen den soliden Implantaten zeigten sich ebenfalls signifikante Unterschiede für die Biegung und axiale Belastung.
    Notizen: Abstract Today there is a variety of different interlocking intramedullary nail designs available for the femur – each designed with a different approach to achieve stability for fracture fixation. We compared different nail types in the bone-implant complex (BIC) of four unreamed solid nails and a slotted, reamed nail to see if there are major differences in stiffness for axial load, bending and torsion. We simulated comminuted mid-shaft fractures by a 2 cm defect osteotomy in paired human cadaver femora. Each bone was tested intact in a Universal testing machine. The results were recorded, osteotomy and osteosynthesis were performed, and the BIC was tested. Relative stiffness was calculated for each individual bone. For P-values less than 0.01 (`least significance difference test') the difference between groups was considered to be significant. In torque testing the unslotted solid nails showed significantly more stiffness (0.6–1.8 Nm/°) compared to the slotted nail (0.2 Nm/°). Compared to intact bone (6.9 Nm/°), both groups of nails were significantly less stiff (relative stiffness 2–20%). In axial load and bending testing, the large-diameter unreamed nail showed greater higher stiffness (32–68%). This study shows that stiffness of the BIC in interlocking femoral nails is more dependent on nail profile than on the press-fit of nails in the medullary canal. For torque stiffness the absence of a slot is of special importance. According to our study, all of the unslotted nails tested give adequate stability for fracture fixation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00008037
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  • 152
    Digitale Medien
    Digitale Medien
    The molecular complex of dibenz[a,c]anthracene and trinitrobenzene (1997)
    Springer
    Structural chemistry 8 (1997), S. 141-147 
    Details
    ISSN: 1572-9001
    Schlagwort(e): Dibenzanthracene ; trinitrobenzene complex ; trinitrobenzene complex ; π-complex ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal structure of the complex between the polycyclic aromatic hydrocarbon di-benz[a,c]anthracene and 1,3,5-trinitrobenzene is reported. The crystals are triclinic, space group P¯1 with unit cell dimensionsa=7.277(2) å,b=11.237(6) å, andc=13.902(5) å,α= 104.13(4)
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262849
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  • 153
    Digitale Medien
    Digitale Medien
    Hydrogen Bonding and Conformational Analysis of Chelate-Stabilized Alkoxopalladium(II) Complexes Derived from Amino Alcohol Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 35-44 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Alkoxopalladium(II) ; Conformational analysis ; Hydrogen bonding ; Two-dimensional and cage structures ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of palladium acetate with two equivalents of di- and triethanolamines RN(CH2CH2OH)2 in the presence of a base affords the new chelate-stabilized alkoxo Pd(II) complexes [Pd(OCH2CH2N(R)CH2CH2OH)2] [R = Me (1), Et (2), n-Bu (3), benzyl (4) or CH2CH2OH (5)]. These N,O-ligated complexes are isolated in high yield as yellow, crystalline solids and are thermally stable despite the presence of several β-hydrogen atoms in the ligand system. Both complexes possess a square-planar palladium coordination geometry with the two oxygen atoms positioned mutually trans. The most notable difference in the molecular structures is that 1 forms a two dimensional network of intermolecular O-H≡O hydrogen bonds, whereas 5 forms intramolecular O-H⃛O hydrogen bonds, which cage the palladium center. In solution 1-4 exist as a diastereoisomeric mixture (a racemic enantiomeric pair SNSN, RNRN and a mesomeric form RNSN) in a 1:1 molar ratio, and this ratio is independent of temperature in nonalcoholic solvents, When complexes 1-4 are dissolved in protic solvents (e.g. MeOH) the diastereomeric excess is temperature-dependent due to an exchange process between the meso diastereoisomer and the (racemic) enantiomeric pair. Thermodynamic parameters for this process in a mixture of MeOH-toluene have been determined with NMR and show this process to be influenced by the steric nature of the alkyl substituent (R) on nitrogen. A conformational analysis based on 1H-NMR coupling constants within the N,O-chelate ring of complexes 1-4 provides details on the solution structure of the ring in both diastereoisomers.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300106
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  • 154
    Digitale Medien
    Digitale Medien
    Synthesis of Functionalized Carbamates through a Palladium-Catalyzed Reductive Carbonylation of Substituted Nitrobenzenes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 13-22 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Carbamates ; Catalysis ; Substituted nitrobenzenes ; Palladium ; Reductive carbonylation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1, 10-phenanthroline)2(triflate)2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. the selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion ot the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid function.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300104
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  • 155
    Digitale Medien
    Digitale Medien
    Dimeric Silver(I) Complexes of Some Isothiazole-Based LigandsDedicated to Prof. Dr. Rolf Gleiter on the occasion of this 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 95-100 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Isothiazole complexes ; Dinuclear silver(I) complexes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of isothiazole-based potential ligands bearing substituents with additional donor sites in the 5-position of the heterocycle was synthesized [3-Me-5-R-C3HNS; R = CH=N(CH2)2py (1), CH=NCH2py (2), CH2N(CH2CH2NEt2)2 (4), (CH2)2SMe (5)]. Upon reaction with AgO3SCF3 they formed complexes [(1)AgOSO2CF3]2 (6), [(2)AgOSO2CF3]2 (7), [(4)Ag]2+2(O3SCF-3)2 (8) and [(5)AgOSO2CF3]2 (9), respectively. 6, 8 and 9 were shown by X-ray structural analyses to consist of dimeric units L2Ag2+2, either discrete (8), coordinated by terminal CF3SO-3 units (6). In 8 and 9 the isothiazole moiety is bonded to the metal center via the ring-N. The coordination potential of the isothiazole heterocycle is discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300115
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  • 156
    Digitale Medien
    Digitale Medien
    Synthesis and Structure of Binuclear Single-Bridged Bis[(phosphane)gold(I)]halogenonium Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 115-118 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Gold complexes ; Bromonium complex ; Halogenonium complex ; Halogen, two-coordinate ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Reactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+ BF-4 obtained from (R3P)AuCl and AgBF4 in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+ BF-4. A number of chloro- (R = Ph, o-Tol, Mes, Bzl, Et), bromo- (R = Ph, o-Tol, Mes) and iodo-bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single-crystal X-ray diffraction. The cations contain two-coordinate bromine atoms with an Au-Br-Au angle of 96.83(3)°.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300119
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  • 157
    Digitale Medien
    Digitale Medien
    A Specific Route to Enantiomerically Pure Asymmetric (η6-Arene)(η4-1,5-cyclooctadiene)Ru(0) ComplexesDedicated to Professor Rolf Gleiter on the occassion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 123-130 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Arene complexes ; Ruthenium compounds ; Electrophilic substitution ; Lithiation ; Catalysis ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6-ligands of (η4-1,5-COD)(η6-1,3,5-cyclooctatriene)Ru (1) or (η4-1,5-COD)(η6-naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono- and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)-(COD)Ru as starting materials. These facilitate a rapid bromine-lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)-(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300121
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  • 158
    Digitale Medien
    Digitale Medien
    Recent Advances in C-F Bond Activation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 145-154 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Fluorocarbons ; C-F bond activation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The main reaction pathways which lead to the breaking of C-F bonds in perfluoroalkanes and -arenes are discussed. Emphasis is placed on recent developments and on the mechanistic patterns that emerge.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300203
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  • 159
    Digitale Medien
    Digitale Medien
    Metal Atoms in the Synthesis of Metal Clusters, VIII.On the Reaction of Sterically Demanding Cyclopentadiene Ligands with Cobalt Atoms: Synthesis, Crystal Structure, Spectroscopic Behavior, and Reactivity of Di-, Tri- and Tetranuclear Hydrido Clusters of CobaltDedicated to Professor IV Siehert on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 161-170 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The metal-vapor reactions of Co atoms with 1,3-tBu2CpH (1a), 1,3-tBu2CpH (1a), 1,2,4-tBu3CpH (1b) and EtMe4CpH (1c) are described. With 1a the two mononuclear complexes [(η5-tBu2Cp) (η4-tBu2-1,3-cyclopentadiene)Co] (2a) and [(η5-tBu2Cp)2Co] (3a) were isolated, together with the dinuclear cobalt cluster [{(η5-tBu2Cp)Co}2H3] (4a) and trace amounts of the tetranuclear cluster [{(η5-tBu2Cp)CoH}4] (5a). The molecular structures of 3a and 4a were determined by X-ray diffraction. Reaction of 1b with Co atoms afforded a single product, the dinuclear cluster [{(η5-tBu3Cp)Co}2H3] (4b), whose molecular structure was determined by single-crystal X-ray diffraction. Both, 4a and 4b exhibit extremely short Co-Co distances [2.244(1) (4a) and 2.242(1) Å (4b)], as found for the Me5Cp analog [{(η5-Me5Cp)Co}2H3] (4c). Reaction of an isomeric mixture of Me4EtCpH (1c) with Co atoms furnished the mononuclear sandwich [ (η5-Me4EtCp)(η4-Me4Et-1,3- cyclopentadiene)Co] (2b), the trinuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}3H4] (6a) and the tetranuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}4H4] (5c). The molecular structure of 5c was determined by X-ray crystallography and revealed a tetrahedral arrangement of the cobalt atoms. The electrochemical behavior of the dinuclear complexes 4a-4c was studied by cyclic voltammetry. Reversible redox couples were found for all three compounds, with a correlation between the degree of alkyl substitution and their respective cathodic shifts. Compounds 4a and 4b react with CO to yield the mononuclear and dinuclear complexes [ (η5- CpR)Co(CO)2] (R=1,3-tBu2, 1,2,4-tBu3) (7a and 7b) as well as [{(η5-CpR)CO}2(CO)2] (8a and 8b). Reaction of the trinuclear hydridocobalt cluster 6a and its Me5Cp analog 6b with AgBF4 in the presence of PEt3 yielded the heteronuclear clusters [{η5-Me4CPR)Co}3AgP(Et)3H4]+[BF4]- (R=Et, Me) (9a and 9b). 9a was structurally characterized by X-ray crystallography.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300205
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  • 160
    Digitale Medien
    Digitale Medien
    Generation and Synthetic Application of Metallated Methyl Isopropenyl Ether, A Substitute for Acetone Enolate (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 45-48 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Metallated methyl isopropenyl ether ; Tetrahydrofurans ; 1-Oxabicyclo[4.3.0]heptanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl isopropenyl ether (1) has been metallated at low temperature with a 1:1 molar mixture of n-BuLi/t-BuOK in THF-hexane, and subsequently functionalized with a variety of electrophilic reagents. At temperatures higher than - 30°C, the metallated methyl isopropenyl ether (2) decomposes with formation of allene. When the suspension of 2 is allowed to warm up to room temperature in the presence of an additional equivalent of n-BuLi, the intermediary allene is converted into 1-propynyllithium (2c), which reacts with propylthiocyanate to give 1-propylthio-1-propyne (4). Some of the functionalization products were subjected to acidic hydrolysis affording the expected methyl ketones.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300107
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  • 161
    Digitale Medien
    Digitale Medien
    Asymmetric Catalysis, 105Part 104: Ref.. Stereoselective Hydrogenation of Folic Acid with Immobilized Optically Active Rhodium(I)/Diphosphane Catalysts (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 55-62 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diastereoselective hydrogenation ; Folic acid ; Immobilized optically active rhodium(I)/diphosphane catalysts ; Leucovorin ; HPLC analysis of 5-formyltetrahydrofolic acid derivatives ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: For the hydrogenation of the C=N bonds in the pyrazine ring of the vitamin folic acid (1) optically active rhodium(I)/diphosphane complexes immobilized on supports such as silica gel or Al2O3 were used. The reduction was carried out at 50 bar hydrogen pressure in an aqueous solution buffered to pH 7. Thus, 5,6,7,8-tetrahydrofolic acid (2) was obtained which contains a new asymmetric center at C-6 of the pterine system. Therefore, in combination with the (S) configuration of the natural L-glutamic acid part of the molecule two diastereomers with (6S,S) and (6R,S) configuration arise. The relatively unstable tetrahydrofolic acid (2) was converted into its 5-formyl derivative folinic acid (4) by treatment with methyl formate/formic acid in a 5:1 mixture of DMSO/pyridine. The Ca salt of folinic acid (4) is the widely used drug leucovorin. The diastereomers were separated by silica gel HPLC. To the column bovine serum albumine (BSA) is covalently bound. With optically active rhodium(I)/diphosphane catalysts, immobilized on silica gel supports, a diastereoselectivity of up to 90% could be achieved in the hydrogenation of folic acid (1).
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300109
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  • 162
    Digitale Medien
    Digitale Medien
    Hexahydro-closo-hexaborane as a Ligand in Coordination Compounds: Syntheses and Crystal Structures of [M2(μ-bis-η3-B6H6)(PPh3)2] )M = Cu, Au) (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 405-408 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Hexahydro-closo-hexaborates ; Boron ; Bridging ligands ; NMR spectroscopy ; Gold ; Copper ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By reaction of (PPh3)3 CuCl and PPh3AuCl with [B6H6]2- in organic media, dinuclear complexes are formed containing the hexaborate as a bridging ligand coordinated to the metal centers by opposite B3 facets of the B6 cluster in a trihapto mode. This is verified by single-crystal X-ray structural analysis of the isotypical (Paā) compounds [Cu2μ-bis-η3-B6H6)(PPh3)2] (1) and [Au2(μ-bis-η3-B6H6)(PPh3)2)] (2) which showed the metal centers to be very close to the B3 plane [1.92 (1), 2.10 (2) Å. The 11B NMR spectra of the two compounds feature doublets, at δ= -15.32 in 1 and at -11.51 in 2, which are significantly shifted downfield in comparison to [B6H6]2- (δ= -17.2).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300315
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  • 163
    Digitale Medien
    Digitale Medien
    Crown Thioether Chemistry: Novel Silver(I) Complexes of 1,3-Dithiole-Annelated 1,4,7-Trithiacyclononane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 425-429 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Silver complexes ; Crown compounds ; Thioethers ; 1,3-Dithioles ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The coordination chemistry of two crown thioethers 2,5,8,10,12-pentathiabicyclo[7.3.0]dodeca-1)9)-ene-11-thione (L) and -11-one (L') with Ag1 has been investigated by structural methods. Both thioethers act as tridentate ligands coordinating the silver ion in a trigonal fashion. In the case L, the 11- thione sulfur is coordinated additionally by another silver ion, to yield a polymeric chain with a distorted-tetrahedral geometry about the metal ion. Despite differing only in its carbonyl chalcogen, L' forms six-coordinated, monomeric complexes.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300319
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  • 164
    Digitale Medien
    Digitale Medien
    Unsymmetric Dinucleating Ligands for Metallobiosite Modelling (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 433-442 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Metallobiosites ; Metalloproteins ; Metalloenzymes ; Dinucleating ligands ; Transition metals ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Awareness of the asymmetric nature of numerous dinuclear metallobiosites and of the ability of the individual metal ions to have quite distinct roles in the functioning of the metalloenzyme concerned has led to a search for carefully designed unsymmetric dinucleating ligands that will give dinuclear complexes capable of acting as models for the metallobiosites. This review surveys progress made in the design and synthesis of complexes capable of serving as models for donor atom, coordination number and geometric asymmetries found at dinuclear metal centres.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300402
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  • 165
    Digitale Medien
    Digitale Medien
    Chemie polyfunktioneller Moleküle, 125Part 124: Ref. Synthese und Kristallstruktur von N,N,N′,N“,N-Pentamethyl-diethylentriamin-cokoordiniertem Kalium-bis(diphenylphosphanyl)amidHerrn Prof. Dr. Gerhard Herberich zum 60. Geburtstage gewidmet. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 141-144 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Alkali metal organophosphanylamide ; Carbon-potassium bonding ; Phosphazane ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The metalation of bis(diphenylphosphanyl)amine [HN-(PPh2)2,1 with KOtBu at 95°C in toluene affords a pale yellow precipitate of potassium bis(diphenylphosphanyl)amide (3a). On addition of liquid N,N,N′,N“,N“-pentamethyldiethylenetriamine (PMDTA, 4) the precipitate dissolves in toluene at 115°C to give a yellow solution, from which yellow-green blocks of [(Ph2P)2NK·PMDTA] (3b) are obtained. X-ray analysis reveals that the coordination sphere of potassium consists of the chelating triamine ligand and [N(PPh2)2]- as N-donor as well as η1 and η2 C-donor with two phenyl fragments. No phosphorus coordination of [N(PPh2)2]- is observed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300124
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  • 166
    Digitale Medien
    Digitale Medien
    Organophosphorus Compounds, 114. Tetracyclic Phosphorus-Aluminium-Carbon Compounds - Synthesis by Cooligomerization of Kinetically Stabilized Phosphaalkynes with Trialkylaluminium CompoundsDedicated to Professor Michael Hanack on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 255-259 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Phosphaalkynes ; Triorganoaluminium compounds ; Cooligomerization ; Cage compounds ; Aluminium compounds ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: When the trialkylaluminium reagents 5 are allowed to react with phosphaalkynes 4 in n-pentane, a highly selective phosphaalkyne cyclotrimerization with incorporation of two organometallic units occurs (→ 6). The tetracyclooctane derivatives 6a-e represent the first examples of phosphorus-aluminium-carbon cage compounds. The polycyclic products 6 are able to function as ligands in transition-metal complexes (→ 7), which is illustrated by the reactions of 6b, c with nonacarbonyldiiron and pentacarbonyl(tetrahydrofuran)tungsten, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300219
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  • 167
    Digitale Medien
    Digitale Medien
    On the Ligating Properties of Sulfonate and Perchlorate Anions Towards Zinc (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 283-289 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Zinc ; Sulfonate ligands ; Perchlorates ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Attempts are reported to incorporate sulfonate and perchlorate anions as ligands in zinc complexes of tripodal ligands. Using tris(benzimidazolylmethyl)amine (BIMA) only the aqua complexes [ (BIMA)Zn-OH2](RSO3)(ClO4) and [(BIMA)Zn-OH2](RSO3)2(R=CH3, CF3, p-tolyl) were accessible. Using substituted pyrazolylborates (Tp*), the same three sulfonate anions were found to be ligands in the complexes Tp*Zn-OSO2R. Spectroscopic evidence for perchlorate coordination in Tp*ZnClO4 · 2 DMSO conflicts with crystallograpic evidence against it in Tp*ZnClO4 · pyridine. The crystal structures of [(BIMA)Zn-OH2](CH3SO3)2, TpCum,MeZn-OS02CH3, TPtBu,MeZn-OSO2C6H4-p-CH3, and [TpCum,MeZn · NC5H5]ClO4 were determined.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300223
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  • 168
    Digitale Medien
    Digitale Medien
    Multiple Bonds Between Main-Group Elements and Transition Metals, CLXIV. Alkylrhenium(VI) Oxides-Synthesis and Characterization (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 295-298 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Rhenium ; Oxides ; Alkyl ligands ; Dirhenium compounds ; Metal-metal interactions ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Most alkylrhenium(VII) oxides, e.g. ((cyclo)-C3H5)Re03 (2) are rather sensitive to temperature and moisture with the prominent exception of methyltrioxorhenium (1). The corresponding alkylrhenium(VI) oxides of formula [RR′(O)- Re(μ-O)]2 [R=R′=(cyclo)-C3H5 (3), iPr (4); R=CH3, R′=C2H5 (5), R=CH3, R′=iPr (6)] are much more stable in this regard. They can be handled in air at room temperature. They were synthesized from Re207 and dialkylzinc precursors, fully characterized and are available in much higher yields than their ReVII congeners. Mixed tetraalkyltetraoxodirhenium(VI) complexes (R # R′) synthesized from 1 and dialkylzinc compounds form as a mixture of cis/trans isomers. They are oily liquids at room temperature. The Re=O and Re-Re stretching force constants as a measure of the bond strengths, were determined from IR and Raman data.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300225
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  • 169
    Digitale Medien
    Digitale Medien
    Hydroxy- and Carboxy-Substituted Allylsilanes: A Simple and Stereoselective Method of Preparation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 335-340 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Allylsilanes ; Superbases ; Metalations ; Stereoselectivity ; Cyclizations ; Silicon ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: When treated with two equivalents of a butyllithium/potassium tert-butoxide mixture, terminal olefins carrying unprotected hydroxy or carboxy groups generate allylmetal intermediates which can be trapped with chlorotrimethylsilane to afford functionalized (Z)-2-alkenyltrimethylsilanes. One equivalent of the superbasic reagent suffices if the unsaturated alcohols are first protected as acetals before being subjected to the metalation/silylation/hydrolysis sequence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300306
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  • 170
    Digitale Medien
    Digitale Medien
    Preparation, Properties, and Reactions, of Metal-Containing Heterocycles, XCVIPart XCV: E. Lindner, E. Bosch, R. Fawzi, M. Steimann, H.A. Mayer, K. Gierling, Chem. Ber. 1996, 129, 945-951.. Mono-, Di- and Trinuclear Metallacycloalkanes of the Iron-TriadDedicated to Professor Wolfgang Beck on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 347-356 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Metallacycloalkanes ; Metallacycloalkenes ; Osmium ; Iron ; Cyclic ketones ; Metallacycles ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of the bis(triflates) [F3CSO3-(CH)m-O3SCF3] [m = 5-10, 12, 14, 16 (1a-i) with Na2[Os(CO)4] in dimethyl either affords the osmacycloalkanes 2a, 2b and 2f-i (m = 5, 6, 10, 12, 14, 16), diosmacycloalkanes 3a-i (m = 5-10, 12, 14, 16), and triosmacycloalkanes 4a-i (m = 5-10, 12, 14, 16). The structure of 3f was investigated by an X-ray structural analysis. This 22-membered disomacycle crystallizes in the space group Pā with Z = 1. If the unsaturated cis-4-octen-1,8-diyl bis(trifluoromethanesulfonate) (5) is treated with Na2[Os(CO)4] the diosmacyclooctadeca-5,14-diene 6 is obtained. By treating the bis(triflates) 1a, b with Na2[Fe(CO)4] the corresponding ferracycloalkanes are formed only in situ. Insertion of carbon monoxide into the M-C σ bonds leads to the cyclic ketones 7a, d and to the diketone 8d.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300308
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  • 171
    Digitale Medien
    Digitale Medien
    Enantioselective Catalysis, XIIIPart XII: U. Nagel, J. Leipold, Chem. Ber., 1996, 129815-821.. Preparative and Structural Chemistry of Chiral 3-(Diphenylphosphanyl)-pyrrolidiens and Their Palladium(II) Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 385-398 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Pyrrolidinephosphanes ; 3-Hydroxypyrrolidine ; 3-Diphenylphosphanylpyronlidine ; Salt effects ; Polymorphism ; Homogeneous catalysis ; Palladium ; Asymmetric catalysis ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The preparation of both enantiomers of 3-diphenylphosphanulpyrrolidiine (2) and several N-substituted derivatives together with two PdIi complexes of this ligand is reported. Form L-malic acid and L-hydroxyproline both enantiomers of 3-hydroxypyrrolidine are prepared without any problems due to epimerization. KPPh2 in the presence of LiCl is shown to be the most effective reagent for the synthesis of 2. The reported X-ray structure determination sof Pdl2 complexes show a rather rigid bicyclic hetero-norbornane skeleton. The flexibility of the other parts of the molecules is obvious in several polymorphs revealed by this method. This polymorphism is additionally investigated by a 31P-CP-MAS study. From solution 1-, 13C- and 31P-NMR studies it is concluded that the bicyclic hetero-norbornane skeleton is retained in solution.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300313
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  • 172
    Digitale Medien
    Digitale Medien
    Reactions of Silicon-Silicon Bonds, VIFor part V, see ref.[1].. Reductive Trichloroslilylation Reactions Leading to Alkyl- and Dialkylaminobis(trichlorosilyl)phosphanesDedicated to Professor Walter Siebert on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 377-384 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Trichlorosilylation ; Dichlorophosphanes ; Silylphosphanes ; Amino(silyl)phosphanes ; Silicon /Reductions ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Reactions of hexachlorodisilane and of trichlorosilane/triethylamine with alkyl-and dialkylaminodichlorophosphanes RPCl2 1a-i [R = iPr: a; (Me3Si)2CH: b; R=1-adamantly: c: R=tBu: d; R=Et2N: e; R=iPr2M: f] furnish bis(trichlorosilyl)-phosphanes RP(SiCl3)2 3a-f. However, when less bulky substituents are attached to the phosphorus atom, so that there is little steric crowding, the double reductive silylations leading from 1 to 3 are accompanied by side reactions and decomposition of 3. Therefore, only 3b, 3c, 3d, and 3f wre isolated in a pure state. These compounds are more readily prepared by the; trichlorosilane/triethylamine method. 1H-, 31P- and 29Si-Nmr spectra confirm their constitution. The structure of solid 3f, the first aminobis(trichlorosilyl)phosphane, was determined by X-ray crystallography. 3f contains a phosphorus atom in a pyramidal environment surrounded by two silicon atoms and a planar nitrogen atom of the diisopropylamino group.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300312
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  • 173
    Digitale Medien
    Digitale Medien
    Formation of the Digallium Compound [(C5C6)2N3](R)Ga-Ga(R)[N3(C6H5)2] with Two Bis(trimethylsilyl)methyl Groups and Two Terminal Chelating Diphenyltriazenido Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 417-420 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Gallium ; Low-valent compounds ; Gallium-gallium bond ; Terminal triphenytriazenido ligand ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Tetrakis[bis(trimethylsilyl)methyl]digallane (4) 1 reacts with 1,3-diphenyltriazene to yield two compounds, which were both characterized by a crystal structure determination. The gallium-gallium bond is retained in the yellow derivate [(H5C6)2N3](R)Ga-Ga(R)[N3(C6H5)2 2 [R = CH(SiMe3)2], which is formed by a ligand exchange reaction and shows two terminal chelating triazenido ligands besides two bis(trimethylsilyl)methyl groups; the Ga—Ga bond length is 245.79(6) pm. The second product is the orange dialkyl(diphenyltriazenido)gallium derivative R2Ga[N3(C6H5)2] 3, where the triazene has reacted as an oxidant by the cleavage of the Ga—Ga bond and probably by release of elemental hydrogen.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300317
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  • 174
    Digitale Medien
    Digitale Medien
    The Electronic Structure of [Te15Br4][MoOBr4]2 and Some General Aspects of Bonding in “Classical” and Hypervalent Tellurium Halides (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 463-472 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Hypervalent compounds ; Tellurium ; Polycations ; Molecular Orbital Theory ; Band structure ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Approximate MO and band structure calculation are used to analyze the bonding in the recently synthesized paramagnetic, semiconducting phase [Te15Br4]2+. The [Te15Br4]2+ chains are very similar to those in the tellurium subhalide Te2Br. The electronic structure and bonding within these chains is analysed and the possibility of hypervalency in both [Te15Br4][MoOBr4]2 and Te2Br is discussed. The bonding in the classically hypervalent molecule TeBr42- and a model Te3Br24- is compared to that of the infinite system. Our calculations indicate that both [Te15Br4][MoOBr4]2 and Te2Br contain weakly hypervalent Te atoms and that the interesting electronic properties of [Te15Br4][MoOBr4]2 arise within the distinct sublattices, which do not interact significantly.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300405
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  • 175
    Digitale Medien
    Digitale Medien
    Heterobimetallic Complexes with a Propynylidene C3-Bridge: General Synthetic Routes to Bimetallic Ethynylcarbene Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 479-488 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Heterobimetallic complexes ; Carbene complexes ; Alkynes ; Coupling reaction ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sequential reaction of the dimethylamino(trimethylsilylethylnyl)carbene complexes [(CO)5M'=C(NMe2)C≡CSiMe3] [M' = W (1a)] with KF/THFMeOH, nBuLi and transition metal halides, [XMLn], affords heterobimetallic propynyliden complexes of the type [(CO)5M'=C(N-Me2)C≡CMLn] [MLn = Ni(PPh3) Cp (4a, b). Ni(PMe2Ph)2- {Mes) (Mes=2,4,6-C6H2Me3) (5a), Rh(CO)(PPh3)2 (6a), Fe(CO)2Cp (7a,b)]. In contrast, reaction of 1a with MeLi · LiBr and [IFe(CO)2Cp] yields the novel N-metallated complex [(CO)5W=C{N(ME)Fe(CO)2Cp}C≡CSiMe3] (8a). The complexes [(CO)5M'=C(NMe2)C≡CMLn=Fe(CO)2Cp (7a, b), Ru(CO)2Cp (10a,b), Ru(CO)(PPh3)Cp (11a), Mn(CO)5 (12a), Re(CO)5 (13a)] are accessible by Pd-catalyzed coupling of the C-stannylated carbene complexes [(CO)5M'=C-(NMe2)C≡CSnBu3] (9a, b) with [XMLn]. The related monomethylaminocarbene complexes [(CO)5M'=C(NHMe)C≡ CSnBu3] (16a, b), obtained by stannylation of [(C))5M'=C(NHMe)C=CH] (15a, B) with Bu3SnNEt2, react with [IFe(CO)2Cp] to give the bimetallic complexes [(CO)5M'=C(NHMe)C≡CFe(CO)2Cp] (17a, b). The complexes 4a, 5a, 7a and 10a were characterized by X-ray structural analysis. The spectroscopic and structural data suggest that the two metal centers in 4-7, 10-13, and 17 interact only weakly.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300407
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  • 176
    Digitale Medien
    Digitale Medien
    Synthesis and Molecular Structure of a Rhenium Complex Derived from 8a-Amino-6-methyl-ergolineDedicated to Professor Roland Mayer on the occasion of his 70th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 839-841 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Rhenium ; Technetium ; 8a-Amino-6-methyl-ergoline ; Chelates ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Current research in radiopharmaceutical chemistry is aimed at the design of technetium-based receptor-binding radiotracers because of the excellent nuclide properties of the isotope 99mTc. Tc tracers and the corresponding complexes of rhenium, as the inactive surrogate of Tc, are required to imitate organic agonists or antagonists of the receptor. We have started studies with ergolines, which are known to be dopamine substitutes. The present report deals with the functionalization of 8α-amino-6-methyl-ergoline (2) with a 2-mercaptoacetyl group, and the subsequent synthesis of the first rhenium complex containing a pendent ergoline moiety [Re- O(SSS)(RS)] (HSSSH = HS-CH2CH2-S-CH2CH2-SH and RSH = 8a-amino-N-(2-mercaptoacetyl)-6-methyl-ergoline) (4). The molecular structure of the rhenium complex was determined by X-ray crystal structure analysis.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300705
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  • 177
    Digitale Medien
    Digitale Medien
    Aminotroponimines as Ligands for Yttrium and Lanthanide Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 859-862 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Yttrium ; Lanthanum ; Samarium ; Lanthanides ; Aminotroponiminate ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of N-isopropyl-2-(isopropylamino)troponimine, [(i-Pr)2ATI]H, with KH in THF affords [(i-Pr)2ATI]K. This is a useful starting material for the preparation of the mono-, bis- and tris-substituted compounds [[i-Pr)2ATI]YCl2-(THF)2}2, [(i-Pr)2ATI2Y[O(2,6,t-Bu2C6H3)] and [(i-Pr)2-ATI]3Ln (Ln = Y, La, Sm), which can be obtained from ([i-Pr)2ATI]K and LnX3 and LnX3 (X = Cl, I), or Y[O(2,6-t-BuC6H3)]3. All compounds have been characterized by spectroscopic methods. The monosubstituted yttrium complex {[(i-Pr)2ATI]YCl2(THF)2}2 has also been investigated by single crystal X-ray diffraction.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300708
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  • 178
    Digitale Medien
    Digitale Medien
    C-H Bond Activation of Simple Alkenes with (C5H5)CO Fragments: Preparation, Molecular Structure, and Dynamical Behaviour of Tri- and Tetranuclear Cyclopentadienylcobalt Cluster complexes with μ-Cycloalkyne Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 593-603 
    Details
    ISSN: 0009-2940
    Schlagwort(e): C-H activation ; Alkyne complexes ; Cyclopentadienyl cobalt ; Fluxionality ; Hydrido complexes ; Clusters ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vicinal C-H bonds of the cycloalkenes CnH2n (n = 5-8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a-5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a-c: n = 5-7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon-carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) å in 5c d; 1.464(8), 1.499(5) Å in 8b, c]. Three dynamic processes - alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange - are operational in the trinuclear 5a-d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300510
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  • 179
    Digitale Medien
    Digitale Medien
    Organoamido- and Aryloxolanthanoids, 15Part 14: Ref. [1a].. Organometallic Compounds of the Lanthanoids, 116Part 115: Ref. [1b].. Syntheses of Low Coordination Number Divalent Lanthanoid Organoamide Complexes, and the X-ray Crystal Structures of Bis[(N-2,6-diisopropylphenyl)(N-trimethylsilyl)amido]bi(tetrahydrofuran)samarium(II)and -ytterbium(II) (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 409-415 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Mercury ; Lanthanides ; Lanthanoid(II) complexes ; (N-2,6-Diisopropylphenyl)(N-trimethylsily)amide complexes ; Bis(trimethylsilyl)amide complexes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The Mercury(II) amide complex Hg[N(SiMe3)(2,6-iPr2C6H3)]2 (1) was prepared by reaction of HgBr2 with Li[N(SiMe3) 2,6-iPr2C6H3)] in diethyl ether solvent. Redox transmetallation reactions of 1 with elemental samarium, europium or ytterbium in THF solvent (THF = tetrahydrofuran), generated the novel divalent complexes Ln[N(SiMe3)(2,6-iPr2C6H3]2(THF)2 with Ln = Sm (2), Eu (3) and Yb (4). 4 was also synthesized by reaction of elemental ytterbium, HgPh2 and HN(SiMe3)(2,6-Me3)2]2(THF)2 [Ln = Sm (5), Yb (6)] by reaction of the metals with HgPh2 and HN(SiMe3)2. Thermal desolvation of 4 under high vacuum gave Yb(N)(SiMe3)2,6-iPr2C6H3)]2 (THF) (7), whereas under identical conditions 6 yielded the solvent-free complex [Yb[N{SiMe3)2]2]2. (8). The new compounds 1-4 and 7 are hydrocarbon soluble and 171Yb-NMR spectra were recorded for 4, 6, 7 and 8. X-ray crystal structure determinations of 2 and 4 revealed four-coordinate, distorted tetrahedral metal environments augmented by weak Ln…ipso-C(aryl) interactions.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300316
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  • 180
    Digitale Medien
    Digitale Medien
    Synthesis and Structure of 2,2′ -Boryl-, Germyl-Silyl-, and Stannyl-Substituted 1,1′ -Binaphthyl SystemsDedicated to Professor Hans Paulsen on the occasion of his 75th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 923-932 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Biaryls ; Boron ; Chirality ; Cooperative Effects ; Lewis acids ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A number of Lewis acid binaphthyl systems, substituted in 2-or 2,2′-position, are synthesized by lithiation of 2,2′-dibromo-1,l ′-binaphthyl (5), followed by addition of various electrophiles. Stepwise lithiation and subsequent borylation with trimethyl borate leads to the bromoboronic acid 6, which can be stabilized by esterification with pinacol giving 7. By increasing the reaction mixture to 2 equiv. of n-butyllithium and 2 equiv. of methyl borate the path to the binaphthylmonoboronic acid ester 9 is opened up. A further increase in the quantity of electrophile also leads to the binaphthylbisboronic acid ester 12. The 2,2′-disubstituted silyl, germyl, and stannyl derivatives 13a-15a are accessible in good yields. Treatment with boron halides leads exclusively to methyl/halogen exchange, giving the bidentate Lewis acids 13b-15b, the former of which can be bridged by oxygen.Only in case of the bis(tributylstannyl)binaphthyl 16a does ipso substitution occur in the presence of boron trichloride, giving the bis(dichloroboryl)-substituted binaphthyl 16b which can then be hydrolysed to 11. The structures of the majority of the compounds were investigated by X-ray diffraction. In case of the 2,2′-disubstituted compounds 13a-15a the naphthyl groups are orientated perpendicular to each other. The intra- and intermolecular interactions are dominated by this binaphthyl system. In case of the oxygenbridged compounds 13c and 14c the angle between the naphthyl planes decreases to about 70°. This also has an effect on the packing of the molecule; in this instance the orientation of two naphthyl in neighbouring molecules is nearly parallel. The structure of the diboronic acid is dominated by intra- and intermolecular hydrogen bonding.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300718
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  • 181
    Digitale Medien
    Digitale Medien
    Temperature-dependent Ring-Opening and -Closure of a Cyclic Phosphane-BoraneDedicated to Professor Gottfried Huttner on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 951-954 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Phosphane-boranes ; Medium-sized rings ; Ring opening and closure ; Temperature-dependent NMR studies ; Phosphorus ; Boron ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A phosphane-borane (3) with the P-B bond integrated into a seven-membered ring was prepared from 4-pentenyl-diphenylphosphane (4) by hydroboration using 9-borabicyclononane (9-BBN). The product was confirmed to have a ring structure in the solid state by single crystal X-ray diffraction. The P-B distance of 2.057(2) Å is indicative of a standard donor-acceptor bond similar to the type found in homologous five- and six-membered rings. The room-temperature 31P-NMR signal of the compound in various solvents (δ ≈ - 15) is not compatible with the cyclic structure and suggests that ring opening occurs as the compound is dissolved. Variable-temperature NMR work corroborated this assumption, and the enthalpy of ring closure was determined to be ΔH = -30.5(4) kJmol-l. In CD2C12 at -90°C, δ31P is shifted to +3.5 ppm to low field, suggesting virtually complete ring closure under these conditions.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300722
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  • 182
    Digitale Medien
    Digitale Medien
    The Coordination Chemistry of Fluorocarbons: Group-I and Group- II Metal Ion Complexes of Fluoro Macrocycles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 963-968 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Fluorine ; Macrocycles ; Complexes ; Sodium ; Barium ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two new fluoro macrocycles BenzoFN2O3 and F(N2O2)2C2H4 were synthesized in the reactions of 1,3-bis(bromomethyl)-2-fluorobenzene with benzo-diaza-15-crown-5 and 1,2-bis(diaza-12-crown-4)ethane, respectively, in 30% yield each. Close CF...metal ion interactions in the respective alkaline metal complexes in solution are evidenced by characteristic shifts of the 19F-NMR resonances of up to δ = 18.7 relative to the free ligand and by a decrease of the 1J(CF) coupling constant of up to 20 Hz, which is most pronounced in BenzoFN2O3 · Li+ and F(N2O2)2C2H4 · K+. In BenzoFN2O3· Li+ a1J(19F-7Li) of 15.5 Hz was observed, which is indicative very close CF...Li+ interactions in solution. In the X-ray crystal structures of BenzoFN2O3 · Na+ [CF⃛Na+ 246.8(2) pm], 26-fluoro-4,7,13,16-tetraoxa-1, 10-diazatricyclo[ 8.8.7.1 20,24 ] - hexacosa-20,22,24(26)triene · Na+ (CF⃛Na+ 267.1(2) pm) and 21 -fluoro-3,6,9,12,15,18-hexaoxabicyclo[ 18.3.1 1,20]heneicosa- l(24),20,22-triene. Ba2+ [CF⃛Ba2+ 299.0(3) pm] short CF⃛metal interactions were found. Such close CF⃛metal ion interactions do not result in a lengthening of the C-F bonds, which is not a sign of weak CF⃛metal ion interactions, since a Cambridge Structural Database search revealed that a shortening of the C-O bond length is also not observed in crown ether complexes of alkaline metals.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300725
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  • 183
    Digitale Medien
    Digitale Medien
    Organophosphorus Compounds, 118Part 2: 117: Ref1. Reactions of 1-Chloro-1H-phosphirenes with Nucleophiles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 711-723 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Phosphorus heterocycles ; 1H-Phosphirenes ; Nucleophilic substitution reactions at 1H-phosphirenes ; Metal-complexation of functionalized 1H-phosphirenes ; Carbonyl complexes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The halogen atoms in the 1-chloro-1H-phosphirenes, 5a-c, are easily substituted on reaction with organolithium and Grignard reagents, 14a-p, with formation of the corresponding O-, N-, C-, Si-, and Ge-substituted 1H-phosphirenes, 15a-t. C1/H exchange reactions also occur on reaction with lithium metal hydrides (5a → 17). Furthermore, substitution reactions are also realized with the alkali metal borates, 18a-g (→19a-g); the same is true for reactions with trimethylsilyl cyanide and azide (→22a-d). Some of the substitution products have been characterized in the form of their metal complexes, 16, 23, 24, and 25.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300607
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  • 184
    Digitale Medien
    Digitale Medien
    Synthesis of Germatranyl Derivatives of Esters of Carboxylic Acids via Organometallic (Si, Ge, Sn) Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 739-746 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Germatranes ; Organotrihalogenogermanes ; Organometallic (Si, Ge, Sn) reagents ; Transmetallation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH2CHROSnAlk3)3 (9-11 (R = H, Me; Alk = Et, Bu), react with X3GeC(R1)(R2)COOR3 (12-17) (X = Cl or Br; R1, R2=H, Me, Ph, SiMe3, COOEt; R3=Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH2CHRO)3GeC(R1)(R2)-COOR3 (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et3SnOMe to give in situ Et3SnC(Ph2)COOMe (23), followed by reaction with GeCl4 to give in situ Cl3GeC(Ph2)COOMe (22 and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH4 in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6 and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300611
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  • 185
    Digitale Medien
    Digitale Medien
    Base-Induced Synthesis of a Tetrastannatriazabicyclo[3.1.1]heptane from Tris)dimethylchlorostannyl)amineDedicated to Professor W. Sieber on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 765-769 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Tin - Nitrogen cage compounds ; Sn—X—Sn intramolecular bridges ; Distannylamine pyridine adduct ; Tin ; Moessbauer spectroscopy ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Tris(dimethylchlorostannyl)amine (2a) reacts with pyridine in a 3:4 molar ratio to produce the tin-nitrogen containing bicyclo[3.1.1]heptane (3) with elimination of the adduct Me2SnCl2·2 py. Treatment of the distannylamine 2,6-[Pr2H3N(SnMe2Cl)2 (4) with pyridine, however, leads to the formation of the 1:1 pyridine adduct 4 and this can be regarded as a model to explain the route to 3. The molecular structures of 3 and 5 were determined by multinuclear magnetic resonance spectroscopy in solution, as well as by X-ray structure analysis of their crystals. Typical structural features for both compounds are intramolecular Sn—X—Sn bridges. Support for the structures comes from MS fragmentation patterns, IR spectra, and the Mössbauer spectra.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300615
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  • 186
    Digitale Medien
    Digitale Medien
    Thermal Reactions of 5-Alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-Phosphapyrazolines) - A Route to Various P—Heterocycles and to 2-PhosphabutadienesDedicated to Professor M. Hanack on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 779-788 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 1,2,4-Diazaphospholes ; Phosphiranes, alkylidene- ; 2-Phosphabutadienes ; Phosphorus heterocycles ; pyrazolines, thermolysis ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 5-alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-phosphapyrazolines) are thermally much more stable than related compounds without the exocyclic double bond. Thermolysis reactions typically occur in the range 110-150°C in toluene solution, and different, mostly competing, reaction pathways are observed. Thermal extrusion of nitrogen from 8a-g gives rise to β-phosphanaylsiloxyalkenes 10, benzo[c]-phosphole derivatives 11, 14 and 115, (β-siloxyalkylidene)-Phosphiranes 12, and dihydro-1,3-oxaphospholes 13. The thermolysis of 5-alkylidene-4,5-dihydro-4-trimethylsilyl-3-trimethylsilyloxy-3H-1,2,4-dizaphospholes 17 afforded three products, including the highly substituted and stable 2-phosphabutadienes 18 formed by nitrogen extrusion and rearrangement. Finally, the 4-chloro-3-trimethylsilyloxy-substituted heterocycle 21 was transformed at 170°C into 4H-1,2,4-diazaphosphole 23. The structures of 13c and 18a were determined by single-crystal X-ray diffraction.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300617
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  • 187
    Digitale Medien
    Digitale Medien
    Reaction of 1,3-Dialkyl-4,5-dimethylimidazol-2-ylidenes with 2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles (Alkyl=iPr and tBu)Dedicated to professor Adolf Zschunke on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 705-710 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Boron ; Diazaboroles ; Carbenes ; Heterocycles ; Imidazoles ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles (3a-c) were synthesized by cyclocondensation of dilithiated 1,4-diazabutadienes (5a-c) with boron tribromide in hexane. 3a was also obtained by sodium amalgam reduction was conducted in ether solvents, diboroxane (2) resulted as the main product. Compound 3a and 1,3-dialkyl-4,5-dimethylimidazol2-ylidenes (6a, b) underwent halide displacement to afford the borolylimidazolium salts 7a, b. Compounds 2, 3a-c, and 7a, b were characterized by elemental analyses and spectroscopic methods (1H, 11B, 13C NMR; Ir; MS). The molecular structures of 2 and 7a were established by single-crystal X-ray diffraction analyses.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300606
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  • 188
    Digitale Medien
    Digitale Medien
    Well-Defined Metallodendrimers by Site-Specific Complexation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 725-728 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Dendrimers ; Metal complexes ; Nanostructures ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Strong multiple complexation of transition metal ions, Cu(II), Zn(II) and Ni(II) with different generations of well-defined poly(propylene imine) dendrimers as multi(tridentate) ligands has been used to construct nanoscopic assemblies of defined structure and size incorporating a distinct number of metal ions from 2 up to 32.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300608
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  • 189
    Digitale Medien
    Digitale Medien
    Compounds of Germanium and Tin, 2lPart 20: Ref.[1]. A Tetraaryldigermene with a Short Germanium-Germanium Double Bond and a Nearly Planar Environment of Both Germanium AtomsDedicated to Professor Hans Bürger on the occasion of his 6oth birthday (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 735-738 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Germanium ; Digermenes ; Tin ; Germylenes ; Stannylenes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Treatment of GeCl2 · dioxane with the Grignard reagent RMgBr (R=2-tBu-4,5,6-Me3C6H) furnishes the tetraaryldigermene R2Ge=GeR2 (8). X-ray structure-analysis of 8 reveals a short Ge=Ge double bond, a nearly planar environment of both germanium atoms and extremely widened C—Ge—C angles of 128°. In solution, 8 dissociates into two germylene molecules R2Ge, which can be trapped with oxygen or by [4+1] cycloaddition reactions with 1,4-dihetero-1,3-dienes. A similar cycloadduct of a stannylene wa obtained by thermolysis of (R′2Sn)3 (R′=2,4,6-iPr3C6H2), in the presence of a 1,4-diazabutadiene and characterized by an X-ray structure-analysis.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300610
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  • 190
    Digitale Medien
    Digitale Medien
    Synthesis and Crystal Structure of tert-Butylamino)di-tert-butyl)siliceniotrichloroaluminate, (Me3C)2Si=NCMe3·AlCl3, and Dimethylazomethine-Aluminium Trichloride, Me2C=NH·AlCl3Dedicated to Prof. A. Meller on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 753-755 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Silicenium ion ; Iminosilane ; Aluminate ; Silicon ; Aluminium ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Lithiated text-butylaminolfluorosilanes react with aluminum trichloride in ether, eliminating LiF to give AlCl3 adducts of iminosilanes  -  aminosiliceniotrichloroaluminates {R2Si-NCMe3·AlCl3}, which thermally form the dimethylazomethine- aluminium trichloride, Me2C=NH·AlCl3.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300613
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  • 191
    Digitale Medien
    Digitale Medien
    Sulfur Compounds, 199Part 198: R. Steudel, Y Drozdova, K. Miaskiewicz, R. H. Hertwig, W. Koch, J Am. Chem. Soc. 1997, 119, 1990.. Novel Titanocene Thiolato Complexes and Their Application in Preparing New Sulfur-Containing Heterocycles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 757-764 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Titanocene complexes ; S ligands ; Organic polysulfanes ; Ligand transfer reactions ; Sulfur heterocycles ; Chalcogens ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Treatment of Cp2Ti(CO)2 (3) with the di- and polysulfanes 1,2,4-(CH2)2S3, C4S6 (9), C,7H10S3 (11), 1,2,4,6-(CH2)3S4 (16), C6H10S6(19), and S6 affords the titanocene chelate complexes Cp2TiS3(CH2)2 (8), (Cp2Ti)2C4S6 (10), Cp2TiS3C7H10 (13), Cp2TiS2C7H10 (14), Cp2TiS4(CH2)3 (17), Cp,2TiS6C6H6H10 (20), and Cp2TiS8 (23). 14 is also obtained from Cp2TiCl2 (1) and the geminal dithiol of norbornene. The analogous reaction with the dithiol of dicyclopentadiene yields Cp2TiS2C10H12 (15). In ligand transfer reactions, 8 reacts with SCl2 to give 1,2,3,5-tetrathiane (25), 10 provides 9 on reaction with Cl2, 13 when treated with S2Cl2 affords C7H10S5 (12), 15 reacts with S2Cl2Cl2 to give C10H12S4. 17 and SCl2 yield 1,2,3,5,7-pentathiepane (18), 20 is converted to C6H10S7 (22) on reaction with SCl2, and 23 yields S10 and 1,2,-C6H4(SCl)2, respectively. With phosgene, thiophosgene, and thionyl chloride, compound 15 yields the corresponding dithiocarbonate 26, the trithiocarbonate 27 and the trisulfane 2-oxide 28. The structure of 27 was determined by X-ray crystallography.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300614
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  • 192
    Digitale Medien
    Digitale Medien
    Synthesis of a Bisdienophilic Phthalocyanine and of Precursors for Repetitive Diels-Alder Reactions Based on Hemiporphyrazines and Phthalocyanines (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 801-806 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Unsymmetrical phthalocyanines ; Hemiporphyrazines ; Macrocyclic bisdienes and bisdienophiles ; Diels-Alder reactions ; Ladder polymers ; Cycloaddition ; Macrocycles ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The specific synthesis of a metal-free bisdienophilic phthalocyanine 193, suitable for repetitive Diels-Alder reactions, is reported. This was achieved by condensation of 191,3,3-trichloro-6/7-nitroioindolenine (191) and 4,9-dibutoxy-2,3,5,8-tetrahydro-1,3-diimino-1H-5,8-epoxybenz[f]isoindoline (2). The ability of 3 to undergo Diels-Alder reactions was tested by reaction with an excess of 1,2,3,4-tetraphenylcyclopentadienone (5). Experimental data of the hemiporphyrazines 9, 10, and 11, which can be used as precursors for the synthesis of ladder polymers, are also given in the Experimental Section.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300620
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  • 193
    Digitale Medien
    Digitale Medien
    Pseudoelement Compounds, XPart IX: Ref. Synthesis and Crystal Structure of New Complexes of the Type trans-[Pt(H)X(PPh3)2 with Cyanamide and Cyanomethanide LigandsDedicated to Professor S. Engels on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1007-1012 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Platinum ; Nitrocyanamide ; Nitrosodicyanomethanide ; 1,1,3, 3-Tetracyano-2-azapropenide ; 1,1,2,3,3-Pentacyanopropenide ; Hydrido complexes ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The new coordination compounds trans-[Pt(H)X(PPh3)2] with NCN- and C(CN)2-functionalized anions (X- = [N(O)C(CN)2]-, [NO2NCN]-, [N{C(CN)2}2]-, [NCC{C-(CN)2}2]-, have been characterized by 1H-, 31P-, 13C-NMR, and IR spectroscopy and elemental analyses the crystal structures of trans-[Pt(H)N(O)C(CN)2(PPh3)2], trans- [Pt(H)N{C(CN)2}2(PPh3)2], and trans-[Pt(H)NCC{C(CN)2}2-(PPh3)2) have been determined by X-ray diffraction. Remarkably, [N(O)C(CN)2]- is coordinated through the central nitrogen atom, while [N{C(CN)2}2]- and [NCC(C(CN)2]2]- are bonded through terminal nitrogen atoms of a C(CN)2 unit.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300730
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  • 194
    Digitale Medien
    Digitale Medien
    New Coupling Reactions and Phosphorylations Using Organozinc Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1021-1027 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Zinc ; Chirality ; Cross-coupling ; Phosphorylations ; Catalysis ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This Microreview on the chemistry of organozinc reagents starts by briefly showing the methods of preparation of organozinc compounds and then discusses the considerable synthetic utility of zinc organometallics for the formation of new carbon-carbon bonds in the presence of transition-metal catalysts. Finally, the use of organozinc chemistry for the preparation of polyfunctional and chiral phosphanes is described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300802
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  • 195
    Digitale Medien
    Digitale Medien
    Synthesis and Structures of Bis(tetramethylipiperidino)aluminum Halides-X-ray Crystal Structures of tmp2AlX (X = Cl, Br, I) and [tmp2A1(μ-F)l2 (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1047-1052 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Bis(tetramethylipiperidino)aluminum halides ; Alkoxy((tetramethylpiperidino)aluminum halides ; 27Al-NMR spectra ; Aluminum ; Amides ; Synthetic methods ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: N-Lithio-2,2,6,6-tetramethylpiperidine [Li(tmp)] reacts with AlX3 (X = Cl, Br) in diethyl ether/ n-hexane solution to generate the products of substitution and ether cleavage, [tmpAl(X)(μ-OEt)], (la, X = Cl; 1b, X = Br). However, when the reaction is allowed to proceed in n-hexane alone, an almost quantitative yield of compounds tmp2AlX (2a, X = Cl; 2b, X = Br; 2c, X = I) is obtained. According to 27AI-NMR spectroscopy, mass spectroscopy, cryoscopy, and X-ray crystal structure determinations, these compounds are monomeric in the solid state, in solution, and in the gas phase. 2b reacts with AgBF4 yielding the fluoride-bridged dimer (tmp2AlF), 2d, as shown by X-ray crystal structure determination.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300805
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  • 196
    Digitale Medien
    Digitale Medien
    Synthesis, Structure, and Dynamic Behavior of (μ-Aldimido)(μ-η1: η2-alkyne)- biszirconocene Cation Complexes That Contain Planar-Tetracoordinate Carbon (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1069-1077 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Planar-tetracoordinate carbon ; Dynamic organometallic systems, μ-alkyne complexes ; π-Agostic systems ; Zirconium ; Metallocenes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The benzonitrile hydrozirconation product Cp2ZrCl(N—CHPh) 8 was treated with propynyl lithium to yield the (propynyl)(benzaldimido)ZrCp; complex 9. Subsequent treatment with trityl tetraphenylborate generated [Cp2Zr(C—C—CH3)-BPh-4] that instantaneously added to 9 to eventually form the (μ-aldimido)(μ-η1:η2-hexadiyne)ZrCp2 cation 11. The X-ray crystal structure analysis showed that 11 contains a planar-tetracoordinate carbon atom that is stabilized by forming a three-center-two-electron bond with the two adjacent metal atoms. Similarly, complex 9 reacted with [Cp2Zr(CH3)+CH3B(C6F5)3 1 to yield the planar-tetracoordinate carbon containing (μ-aldimido)(μ-η1:η2-2-butyne) Cp; cation 12. Both complexes 11 and 12 exhibit dynamic NMR spectra due to their rapid reorganization of the dimetallabicyclic frameworks (ΔG* = 10 kcal mol-1) in addition to an anchimerically assisted C—N bond rotation (ΔG* =15 kcal mol-1).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300808
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  • 197
    Digitale Medien
    Digitale Medien
    Isolation and Characterization of a Porphinatomanganese(IV) Complex from the Reaction of Dichloro Monoxide with 5,10,15,20-Tetrakis-(2,6-dichloropheny)porphinatomanganese(III) Chloride [Mn(EDCPP)CI] (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1099-1103 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Porphyrinatomanganese(IV) ; Monooxygenase model ; Dichloro monoxide ; Catalytic alkene epoxidation ; Catalytic alkane oxygenation ; Catalytic alkane chlorination ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The isolation at -78°C and characterization of the novel crystalline reactive porphinatomanganese(IV) complex Mn-(TDCPP)(OCl)2 (5) is described. 5 is compared with the porphinatomanganese(IV) complexes Mn(TDCPP)(C6H5IOCl)2 (2), Mn(TDCPP)(C6F510C1)CI (3) and Mn(TDCPP)(OCH3)2, (4). The stoichiometric reaction of 5 with triphenylphosphane yields 2.5 equivalents of triphenylphosphane oxide and 1.0 equivalent of Mn(TDCPP)Cl (1). Complex 5 epoxidizes stilbene, and oxygenates and chlorinates cyclohexane.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300811
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  • 198
    Digitale Medien
    Digitale Medien
    Synthesis and Structure of Allenyl-Substituted η6-Benzene(tricarbonyl)-chromium Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1135-1139 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Arene complexes ; Chromium ; Allenes ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The Cr(CO)3-complexed η6-phenylpropargylic alcohols 3 react in a displacement rearrangement with thionyl chloride or chlorodiphenylphosphane to give the chloro- or phosphoryl allenyl substituted η6-phenyl complexes 4 and 6, respectively. In the X-ray crystal structure of the novel organometallic allenic derivatives 4b and 6b the vicinal chloro or phosphoryl substituent and the benzene(tricarbonyl)chromium fragment are arranged coplanarily. Palladium/copper-catalyzed couplings of the chloroallene 4b with terminal alkynes disclose a facile access to ynallene derivatives 8, novel carbon-rich organometallic π-systems.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300816
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  • 199
    Digitale Medien
    Digitale Medien
    Raman and Infrared Spectra and Quantum Chemical Calculations for Trichlorophosphoranylidenesulfamoyl Chloride, CISO2N=PCI3 (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1141-1145 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Trichlorophosphoranylidenesulfamoyl chloride ; Vibrational spectroscopy ; Conformational properties ; Quantum chemical calculations ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Raman (3500-50 cm-l) and infrared (4000-400 cm-l) spectra of the title compound, ClSO2N=PCl3, were recorded for the solid and liquid phase. Additionally, the Raman spectrum of the compound dissolved in CCl4 was obtained and qualitative depolarization values were determined. The spectra of the liquid and solid phase were interpreted in terms of the existence of only one conformation possessing C1 symmetry, as predicted by quantum chemical calculations. A complete vibrational assignment is proposed based on the relative intensities, on group frequencies along with support from the normal coordinate analysis. The experimental fundamental vibrational modes are compared to those obtained from theoretical approaches employing the ab initio MP2/6-31G* method and a density functional approximation (B3PW91/6-31G*).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300817
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  • 200
    Digitale Medien
    Digitale Medien
    Ab Initio Studies on Disubstituted closo-Icosahedral Heteroboranes, X2B10H10 [X = CH, SiH, N, P, and Sb] (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1147-1150 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Icosahedral heteroboranes ; Ab initio calculation ; Bonding models ; Aromaticity ; Nucleus Independent Chemical Shift [NICS] ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ab initio theoretical studies on X2B10H10 (X = CH, SiH, N, P and Sb) have been done for all the three possible isomers. Unlike lower-vertex heteroboranes, all the hetero derivatives have shown similar trends in the relative stabilities, the 1,12-isomer being more stable followed by 1,7- and 1,2-isomers, except for N and Sb. No conventional 1,2-isomer for N could be found. Instead, a new nido isomer which is 18.1 kcal/mol higher in energy than the most stable isomer has been located. Any hetero group substitution to icosahedral R12H122- is found to be thermodynamically destabilizing. However, the Nucleus Independent Chemical Shift criterion shows that all compounds, except for 8, have similar aromaticity.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300818
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