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Notes: Abstract Minimum onset latency (Lmin) of single- and multiple-unit responses were mapped in the primary auditory cortex (AI) of barbiturate-anesthetized cats. Contralateral Lmin for multiple units was non-homogeneously distributed along the dorso-ventral/isofrequency axis of the AI. Responses with shorter latencies were more often located in the central, more sharply tuned region while longer latencies were more frequently encountered in the dorsal and ventral portions of the AI. For single units, a large scatter of Lmin values was found throughout the extent of the AI including cortical depth. The relationship between Lmin and previously reported spectral, intensity and temporal parameters was analyzed and revealed statistically significant correlations between minimum onset latency and the following response properties in some but not all studied animals: sharpness of tuning of a frequency response area 10 dB above threshold, broadband transient response, strongest response level, monotonicity of rate/level functions, dynamic range, and preferred frequency modulation sweep direction. This analysis suggests that Lmin is determined by several independent factors and that the prediction of Lmin based on relationships with other spectral and temporal response properties is inherently weak. The spatial distribution and the functional relationship between these response parameters may provide an important aspect of the time-based cortical representation of specific features in the animal's natural environment.

Notes: Abstract The reinnervation pattern of crural pacinian corpuscles was examined by light and electron microscopy in eight adult cats of both sexes 3–18 months after sciatic nerve crush. Normal pacinian corpuscles are each supplied with a single myelinated axon and a single cylindrical axon terminal which may branch in the distal part of the inner core. Reinnervation of these vibroreceptors was very satisfactory after sciatic nerve crush: in a sample of 68 corpuscles examined 3–18 months after the operation, 92.6% were found reinnervated, while only 7.4% remained denervated. At the nerve entry, 84.2% of the reinnervated corpuscles were supplied with a single myelinated axon, while 15.8% received two myelinated axons; some of the axons branched before or after entering the inner core. Near the mid-level of the inner core, 60.3% of 63 reinnervated corpuscles were innervated with a single axon terminal, 22.2% were biterminal, while 17.5% had three or more terminals. Regenerated axon terminals induced the formation of thin lamellar layers in the axial region of the original core and, exceptionally, also at the outer aspect of the original core. In monoterminal corpuscles, the shape and ultrastructure of regenerated endings resembled those of normal controls, whereas in multiterminal corpuscles their shape and profiles were variable. In contrast to previous reports, reinnervated corpuscles did not ultimately become monoterminal. On the contrary, the mean number of 1.3 terminals found in reinnervated crural corpuscles at 3–5 months increased to 1.9 terminals per corpuscle 6–18 months after axotomy.

Notes: Abstract  In this study we examined connections between the moment-generating capacity of the neck muscles and their patterns of activation during voluntary head-tracking movements. Three cats lying prone were trained to produce sinusoidal (0.25 Hz) tracking movements of the head in the sagittal plane, and 22.5º and 45º away from the sagittal plane. Radio-opaque markers were placed in the cervical vertebrae, and intramuscular patch electrodes were implanted in five neck muscles, including biventer cervicis, complexus, splenius capitis, occipitoscapularis, and rectus capitis posterior major. Videofluoroscopic images of cervical vertebral motion and muscle electromyographic responses were simultaneously recorded. A three-dimensional biomechanical model was developed to estimate how muscle moment arms and force-generating capacities change during the head-tracking movement. Experimental results demonstrated that the head and vertebrae moved synchronously, but neither the muscle activation patterns nor vertebral movements were constant across trials. Analysis of the biomechanical model revealed that, in some cases, modification of muscle activation patterns was consistent with changes in muscle moment arms or force-generating potential. In other cases, however, changes in muscle activation patterns were observed without changes in muscle moment arms or force-generating potential. This suggests that the moment-generating potential of muscles is just one of the variables that influences which muscles the central nervous system will select to participate in a movement.

Notes: Abstract  For an understanding of how various degrees of altered use (training, disuse) affect the properties of skeletal muscles, it is important to know how much they are used normally. The main aim of the present project was to produce such background knowledge for hindlimb muscles of the cat. In four adult female cats, each one being studied in several experimental sessions, ankle muscles were chronically implanted with electrodes for electromyographic (EMG) recording. The muscles recorded from were: extensor digitorum longus (EDL), peroneus longus (PL), tibialis anterior (TA), lateral gastrocnemius (LG) and soleus (SOL). For PL, TA and LG, there were anterior as well as posterior recording sites. During 24-h experimental sessions, the studied animal stayed, together with another cat, in a box large enough for playing and walking around. Using telemetric techniques, samples of EMG signals were recorded on tape for 4 min every 30 min. In an off-line analysis, measurements were made of the total accumulated duration of activity from each one of the studied muscle regions. These ”duty times” were expressed as a percentage of total sampling duration. When averaged over the whole 24-h experimental period, the mean duty times per muscle region varied from 1.9% for EDL up to about 13.9% for SOL. Also, among predominantly fast muscles of mixed-fibre composition (i.e. all studied muscles except SOL), marked and statistically significant differences in duty time were found, mean values varying fivefold from 1.9% (EDL) to 9.5% (PL, posterior site). For all three muscles with simultaneous recordings from different sites, consistent and statistically significant differences in daily duty time were found between anterior and posterior regions (anterior less than posterior for TA and PL; anterior more than posterior for LG). We also measured the extent to which each 4-min sampling period was filled with activity (if any). As compared to muscles with a low mean 24-h duty time, those with high duty times were not active during more sampling periods per day, but, whenever being used, their activity lasted relatively longer. Such results were consistent with the view that differences in mean 24-h duty time might largely reflect differences in the extent to which the various muscles and muscle regions were used for long-lasting stabilizing contractions.

Notes: Abstract Results of previous studies have indicated that the rostral superior colliculus (SC) plays an important part in the control of accommodation. The present study was carried out to investigate retinal projections to the accommodation-related area in the rostral SC. We injected WGA-HRP into the accommodation-related area in the rostral SC of the cat, where accommodative responses were elicited by stimulation with weak currents of less than 20 μA. Following injection of WGA-HRP into the accommodation-related area in the rostral SC, retrogradely labeled ganglion cells were observed mainly in the area centralis. Projections from the contralateral eye were denser than those from the ipsilateral eye. Almost all retrogradely labeled cells were classified as γ-cells owing to their small cell-body diameters and thin dendrites, although a few were classified as α-cells. These findings suggest that the accommodation-related area in the rostral SC is located in the portion corresponding to the area of representation of the central visual field and receives mainly γ-cell projections

Notes: Abstract  In decerebrate cats that had been acutely hemilabyrinthectomized (HL), the extracellular activities of vestibular nuclear neurons on the lesioned and labyrinth-intact sides were studied during constant-velocity off-vertical axis rotations (OVAR) in the clockwise (CW) and counterclockwise (CCW) directions (at 10° tilt). Over the range of 1.75–15°/s, two types of neuronal responses were identified on both sides. Some neurons showed symmetric and velocity-stable bidirectional response sensitivity (δ defined as the CW gain over the CCW gain) while other neurons exhibited asymmetric and velocity-variable δ. The mathematically derived gain tuning ratios of these two groups of neurons were within the range of one-dimensional and two-dimensional neurons respectively. The best response orientations in one-dimensional neurons and the orientations of the maximum response vector, S max, in two-dimensional neurons were found to point in all directions on the horizontal plane. On the labyrinth-intact side, both the one-dimensional and two-dimensional neurons showed asymmetry in the neuron numbers and/or the response gains between the two roll quadrants as well as between the two pitch quadrants. In addition, both the neuron number and gain were significantly higher for neurons in the head-down/ipsilateral-side-down half-circle than those in the head-up/contralateral-side-down half-circle. None of the aforementioned asymmetries was observed on the lesioned side. That a comparable pattern of distribution was observed in the one-dimensional and two-dimensional neurons suggests that these neurons maintain a common spatial reference frame in encoding head orientational signals arising from the ipsilateral and contralateral otoliths. Furthermore, a predominance of two-dimensional neurons that exhibited a greater gain with CW rotations was observed on both sides of HL cats. Of the response dynamics observed amongst neurons on the two sides of HL cats, no difference was found with regard to the response gain and the pattern of response lead. However, a difference in response lag was observed between neurons on the two sides of HL cats. These suggest that there is a segregation of otolithic signals to reach the ipsilateral and contralateral vestibular nuclei. Taken together, the present study demonstrates that one-dimensional and two-dimensional neuronal responses could be elicited with inputs arising solely from the ipsilateral or contralateral otoliths. The observed orientational tuning and the CW-CCW asymmetry to bidirectional rotation may provide the essential directional coding of head orientations. Further, the imbalance of spatial/dynamic response patterns between the bilateral vestibular nuclei following the restriction of otolith inputs by HL implies that converging otolithic inputs from the bilateral labyrinths are essential for producing the neuronal responses in control animals. The results are also discussed in terms of the possible contribution of the various neural asymmetries between neuronal subpopulations in the bilateral vestibular nuclei to the behavioral symptoms accompanying acute HL.

Notes: Abstract  A technique was developed to measure, in the anesthetized and paralyzed cat under artificial ventilation, changes of excitability to intraspinal stimulation simultaneously in two different afferent fibers or in two collaterals of the same afferent fiber. Intraspinal stimulation reduced the threshold of single muscle afferent fibers ending in the intermediate nucleus. This effect was seen with strengths below those required to activate the afferent fiber tested (1.5–12 μA), occurred at a short latency (1.5–2.0 ms), reached a maximum between 15 and 30 ms, and lasted up to 100 ms. The effects produced by graded stimulation applied at the shortest conditioning-testing stimulus time intervals increased by fixed steps, suggesting recruitment of discrete elements, most likely of last-order interneurons mediating primary afferent depolarization (PAD). The short-latency increases in excitability produced by the weakest effective intraspinal stimuli were usually detected only in the collateral closest to the stimulating micropipette, indicating that the stimulated interneurons mediating PAD have spatially restricted actions. The short-latency PAD produced by intraspinal stimuli, as well as the PAD produced by stimulation of the posterior biceps and semitendinosus (PBSt) nerve or by stimulation of the bulbar reticular formation (RF), was depressed 19–30 min after the i.v. injection of 0.5 mg/kg of picrotoxin, suggesting that all these effects were mediated by GABAergic mechanisms. The PAD elicited by stimulation of muscle and/or cutaneous nerves was depressed following the i.v. injection of (–)-baclofen, whereas the PAD elicited in the same collateral by stimulation of the RF was baclofen-resistant. The short-latency PAD produced by intraspinal stimulation was not always depressed by i.v. injections of (–)-baclofen. Baclofen-sensitive and baclofen-resistant monosynaptic PADs could be produced in different collaterals of the same afferent fiber. The results suggest that the intraspinal terminals of single muscle afferents receive synapses from more than one PAD-mediating GABAergic interneuron and that a single last-order interneuron has synaptic connections with a restricted number of intraspinal terminals and/or collaterals of the same afferent fiber. In addition, they support the existence of separate subsets of last-order baclofen-sensitive and baclofen-resistant interneurons that respond predominantly to segmental and to descending inputs. It is suggested that the restricted nature of the PAD plays an important role in the central control of the synaptic effectiveness of group I muscle afferents.

Notes: Abstract  The purpose of this study was to determine (1) whether the nucleus retroambigualis (NRA) plays an essential role in periaqueductal gray (PAG)-induced vocalization and (2) which NRA neurons are involved in the projection from the PAG to laryngeal motoneurons. Bilateral injections of the neurotoxin kainic acid into the NRA in decerebrate cats abolished PAG-induced vocalization; PAG stimulation after the injections no longer modulated vocal fold adductor or tensor activity, and only tonically, but no longer phasically, activated the abdominal muscles. In contrast, PAG-induced inspiratory excitation remained even after the injections. These results suggest that the NRA is essential for the vocal activation of the laryngeal adductor and abdominal muscles, and that an additional pathway from the PAG to respiratory motoneurons other than through the NRA is important for mediating PAG-induced inspiratory activation. Secondly, axonal projections of NRA neurons to the contralateral nucleus ambiguus (NA) were studied electrophysiologically. Five expiratory neurons, which had decrementing (n=4) or constant (n=1) firing patterns, were identified as both having axonal projections to the NA and receiving inputs from the PAG. Furthermore, following NA stimulation many constant-latency action potentials of silent cells were recorded in the vicinity of the NRA, where many silent cells were also orthodromically activated by PAG stimulation. No NRA augmenting expiratory neurons could be antidromically activated from the NA. It is suggested that the NRA and adjacent reticular formation integrate inputs from the PAG and send outputs to laryngeal motoneurons for vocalization.

Notes: Abstract  Previous studies have reported that stimulation of group I afferents from extensor muscles prolongs stance duration during walking in decerebrate cats. The main objective of this investigation was to determine whether this phenomenon occurs during walking in conscious cats. In conscious cats without lesions of the central nervous system (CNS), stimulation of group I afferents in the lateral gastrocnemius/soleus (LGS) nerve during stance prolonged extensor burst duration and increased the cycle period in five of seven animals. The mean increases in cycle period were modest, ranging from 6 to 22%. In five of six animals that walked both quadrupedally and bipedally at the same rate, the effects on cycle period were stronger during bipedal stepping (18% mean increase in cycle period compared with 9%). The stimulated nerves were transected and the experimental procedure was usually delayed in the conscious animals for 2–3 days following implantation of the stimulating electrodes. To assess whether chronic axotomy of the LGS nerve was a factor in the decreased effectiveness, four of the cats with chronic nerve section were decerebrated and their LGS nerves were stimulated after the animals began to spontaneously walk on a motorized treadmill. In all four of these animals, the effects of stimulating the chronically cut LGS nerve on the step cycle period became stronger following decerebration. However, these effects were not as strong as those produced when an acutely sectioned LGS nerve was stimulated. During both quadrupedal and bipedal walking, stimulation of the LGS nerve increased the amplitude of the medial gastrocnemius (MG) electromyogram. The augmented activity of the MG muscle contributed to an increased extension of the ankle during stimulated steps. The conclusion from these experiments is that stimulation of the group I afferents in extensor nerves can prolong stance in the conscious cat, but this effect is weaker than in decerebrate animals. It is likely that transmission in the polysynaptic group I pathways controlling stance duration is regulated in a complex fashion by descending signals from the brain in the conscious animal.

Notes: Abstract  In the ventral horn of the lumbar spinal cord of cats anaesthetised with pentobarbitone sodium, microelectrophoretically administered (–)-baclofen, but not (+)-baclofen, reversibly reduced the duration of the orthodromic action potential of muscle group Ia afferent terminations, but not those of muscle group I afferent myelinated fibres. The presumably submicromolar concentrations are already known to reversibly reduce excitatory transmitter release from muscle group Ia afferent terminations. Action potential durations were estimated from threshold recovery curves after an orthodromic impulse using an extracellular microstimulation technique. Both of these presynaptic effects of (–)-baclofen were blocked by baclofen antagonists, and neither appeared to be reduced by the potassium channel blocking agents tetraethylammonium and 4-aminopyridine. Tetraethylammonium and 4-aminopyridine also did not significantly modify the reduction by (–)-baclofen of monosynaptic field potentials in the lumbar cord of rats anaesthetised with pentobarbitone sodium. In the cat the maximum reduction by (–)-baclofen of termination action potentials was considerably less than that produced by cadmium ions, which, unlike (–)-baclofen, also reduced the action potential duration of group I myelinated fibres. These findings are consistent with a reduction by (–)-baclofen of the influx of calcium through voltage-activated channels in the membrane of group Ia terminations, a proposal which also accounts for the reduction by (–)-baclofen of the release of GABA at axo-axonic depolarizing synapses on these terminations. The results are discussed in relation to the mode of action of (–)-baclofen and the different sensitivities of transmitter release at various central synapses.

Notes: Abstract  A region of the caudal ventrolateral medullary reticular formation (CVLM) participates in baroreceptor, vestibulosympathetic, and somatosympathetic reflexes; the adjacent retroambigual area is involved in generating respiratory-related activity and is essential for control of the upper airway during vocalization. However, little is known about the connections of the CVLM in the cat. In order to determine the locations of terminations of CVLM neurons, the anterograde tracers Phaseolus vulgaris leucoagglutinin and tetramethylrhodamine dextran amine were injected into this region. These injections produced a dense concentration of labeled axons throughout the lateral medullary reticular formation (lateral tegmental field), including the retrofacial nucleus and nucleus ambiguus, regions of the rostral ventrolateral medulla, the lateral and ventrolateral aspects of the hypoglossal nucleus, nucleus intercalatus, and the facial nucleus. A smaller number of labeled axons were located in the medial, lateral, and commissural subnuclei of nucleus tractus solitarius, the A5 region of the pontine reticular formation, the ventral and medial portions of the spinal and motor trigeminal nuclei, locus coeruleus, and the parabrachial nucleus. We confirmed the projection from the CVLM to both the rostral ventrolateral medulla and lateral tegmental field using retrograde tracing. Injections of biotinylated dextran amine or Fluorogold into these regions resulted in retrogradely labeled cell bodies in the CVLM. However, the neurons projecting to the lateral tegmental field were located mainly dorsal to those projecting to the rostral ventrolateral medulla, suggesting that these neurons form two groups, possibly with different inputs. Injections of retrograde tracers into the lateral tegmental field and rostral ventrolateral medulla also produced labeled cell bodies in other regions, including the medial and inferior vestibular nuclei and nucleus solitarius. These data are consistent with the view that the CVLM of the cat is a multifunctional area that regulates blood pressure, produces vocalization, affects the shape of the oral cavity, and elicits contraction of particular facial muscles.

Notes: Abstract  This study was primarily aimed at investigating the selectivity of the cortico-spinal actions exerted on the pathways mediating primary afferent depolarization (PAD) of muscle spindle and tendon organ afferents ending within the intermediate nucleus at the L6–L7 segmental level. To this end we analyzed, in the anesthetized cat, the effects produced by electrical stimulation of sensory nerves and of the cerebral cortex on (a) the intraspinal threshold of pairs of single group I afferent fibers belonging to the same or to different hindlimb muscles and (b) the intraspinal threshold of two collaterals of the same muscle afferent fiber. Afferent fibers were classified in three categories, according to the effects produced by stimulation of segmental nerves and of the cerebral cortex. Twenty-five of 40 fibers (62.5%) were depolarized by stimulation of group I posterior biceps and semitendinosus (PBSt) or tibialis (Tib) fibers, but not by stimulation of the cerebral cortex or of cutaneous and joint nerves, which instead inhibited the PBSt- or Tib-induced PAD (type A PAD pattern, usually seen in Ia fibers). The remaining 15 fibers (37.5%) were all depolarized by stimulation of the PBSt or Tib nerves and the cerebral cortex. Stimulation of cutaneous and joint nerves produced PAD in 10 of those 15 fibers (type B PAD pattern) and inhibited the PBSt- or Tib-induced PAD in the 5 remaining fibers (type C PAD pattern). Fibers with a type B or C PAD pattern are likely to be Ib. Not all sites in the cerebral cortex inhibited with the same effectiveness the segmentally induced PAD of group I fibers with a type A PAD pattern. With the weakest stimulation of the cortical surface, the most effective sites that inhibited the PAD of individual fibers were surrounded by less effective sites, scattered all along the motor cortex (area 4γ and 6) and sensory cortex (areas 3, 2 and 1), far beyond the area of projection of group I fibers from the hindlimb. With higher strengths of cortical stimulation, the magnitude of the inhibition was also increased, and previously ineffective or weakly effective sites became more effective. Maps obtained when using the weakest cortical stimuli have indicated that the most effective regions that produced PAD of group I fibers with a type B or type C PAD pattern were also scattered throughout the sensory-motor cortex, in the same general area as those that inhibited the PAD of group I afferents with a type A PAD pattern. In eight fibers with a type A PAD pattern it was possible to examine the intraspinal threshold of two collaterals of the same single afferent fiber ending within the intermediate nucleus at the L7 segmental level. In six fibers, stimulation of the PBSt nerve with trains of pulses between 1.5 and 1.86 times threshold (×T) produced a larger PAD in one collateral than in the other. In seven fibers, stimulation of the sensory-motor cortex and of cutaneous nerves produced a larger inhibition of the PBSt-induced PAD in one collateral than in the other. The ratio of the cortically induced inhibition of the PAD elicited in the two collaterals could be modified by changing the strength of cortical and of PBSt stimulation. In three fibers it was possible to inhibit almost completely the background PAD elicited in one collateral while having little or no effect on the PAD in the other collateral. Changes in the intraspinal threshold of pairs of collaterals following electrical stimulation of segmental nerves and of the somato-sensory cortex were examined in three fibers with a type B and two fibers with a type C PAD pattern. In four fibers the PAD elicited by stimulation of cutaneous (4–20×T) and muscle nerves (1.54–3.7×T), or by stimulation of the sensory-motor cortex, was of different magnitude in the two collaterals. In two experiments it was possible to find cortical sites in which weak surface stimulation produced PAD in one collateral only. The magnitude of the PAD elicited in pairs of collaterals of group I afferents with a type B or C PAD pattern, or the inhibition of the PAD in pairs of collaterals of fibers with a type A PAD pattern, appeared not to be topographically related to the site of spinal projection of the cutaneous and cortico-spinal fibers used for conditioning stimulation. The present demonstration of a differential control of the PAD exerted on two collaterals of the same afferent fiber suggests that the profuse intraspinal branching of muscle spindle and tendon organs is a potentially rich substrate for information transmission. By means of presynaptic control mechanisms, the terminal arborizations of the afferent fibers could function either as a simple unit or in a fractionated manner, allowing funneling of information to selected groups of central neurons.

Notes: Abstract  The central cervical nucleus (CCN) of the cat receives input from upper cervical muscle afferents, particularly primary spindle afferents. Its axons cross in the spinal cord, and while in the contralateral restiform body give off collaterals to the vestibular nuclei. In order to study the connections between CCN axons and vestibular neurons, we stimulated the area of the CCN in decerebrate cats while recording intra- or extracellularly from neurons in the contralateral vestibular nuclei. CCN stimulation evoked excitatory postsynaptic potentials (EPSPs) or extracellularly recorded firing in the lateral, medial and descending vestibular nuclei. The latency of EPSPs (mean 1.6 ms) was on average 0.4 ms longer than the latency of antidromic spikes evoked in the CCN by stimulation of the contralateral vestibular nuclei (mean 1.2 ms), demonstrating that the excitation was typically monosynaptic. The results provide further evidence that the CCN is an important excitatory relay between upper cervical muscle afferents and neurons in the contralateral vestibular nuclei.

Notes: Abstract  The ventrolateral (VL) thalamus in mammals is a site well-situated to show vocalization-related neural activity if there is general or classical motor system involvement in vocal production. It receives input from both the basal ganglia and cerebellum, and forms reciprocal connections with motor cortical areas. The current study examined the activity in cat VL thalamus neurons during instrumentally conditioned vocalization. Units in our sample showed irregular spontaneous firing which could be modulated by slowly occurring fluctuations in intensity of vocalization task performance. Two main types of behavioral events were associated with changes in neural firing rate. The first of these was the ingestion of food reward. More than half of all recordings showed phasic bursting patterns during licking; a similar number had increases in firing preparatory to this phasic activity. The second behavioral event modulating unit responses was vocalization. Approximately 60% of recordings showed activity changes time-locked to vocalization. These responses were almost always excitatory, and often involved changes in firing that preceded vocalization onset. No spatial organization of differences in firing pattern between neurons could be distinguished. Our results suggest that VL thalamus may well be involved in mediating vocal behavior, although its functional role remains an object of speculation. Results are compared with previous studies of vocalization-related activity and of VL thalamus activity.

Notes: Abstract  In a proportion of simple cells of the striate cortex, the weighting functions of the receptive fields (RFs) had more periods than could be established by mapping using responses to light bars and dark bars. In these multiperiodical cells, side subfields do not respond to single bars, as they have lower weights than central zones and the excitation is under the threshold of impulse response if a single bar is applied. This fact has been established by different methods: conditioning and testing stimuli, grating patches, and inverse Fourier transform of the amplitude-phase characteristic, combining them in one cell. We assume that this type of nonlinarity can be used in analyzing the image, as it acts as a spatial-frequency filter of the area overlapped by the RF. The responses to complex gratings composed by two sinusoidal gratings of different frequency, contrast, and phase shift were compared with the sum of the responses to the gratings when they were presented separately. The results show that the principle of superposition holds a reasonable approximation even if the response is evoked from the side subzones. Some simple cells have nonlinear properties beyond the classic zone of RF (2nd type of nonlinearity). Linear cells have a tendency to be localized in layer 4 of striate cortex, cells with a nonlinear surround in layers 2, 3, 5, and 6. The significance of both types of nonlinearities in simple cells is discussed.

Notes: Abstract  Axonal pathways, projection levels, conduction velocities, and locations of the cell bodies of saccular nerve-activated vestibulospinal neurons were studied in decerebrated cats and anesthetized cats, using a collision test of orthodromic and antidromic spikes. The saccular nerve was selectively stimulated by bipolar tungsten electrodes. Three monopolar electrodes were inserted into the left and right lateral vestibulospinal tract (LVST) and medial vestibulospinal tract (MVST) of the C1 segment, to determine the pathway of axons. Three pairs of similar electrodes were positioned bilaterally in the C3–4, T1, and L3 segments to examine projection levels. Another monopolar electrode was placed in the oculomotor nucleus to determine whether saccular nerve-activated vestibulospinal neurons have branches ascending to the oculomotor nucleus. Of 145 vestibular neurons orthodromically activated by stimulation of the saccular nerve, 46 were activated from the C1 segment antidromically. Forty-three were second-order vestibulospinal neurons and 3 were third-order vestibulospinal neurons. Four saccular nerve-activated vestibulospinal neurons were also antidromically activated from the oculomotor nucleus. Sixty-three percent of the saccular nerve-activated vestibulospinal neurons descended through the MVST; one-third of these terminated in the upper cervical segments, one-third reached the lower cervical segments and the remaining one-third reached the upper thoracic segments. Thirty percent of the saccular nerve-activated vestibulospinal neurons descended through the ipsilateral LVST; most of these reached the upper thoracic segments. Seven percent of the saccular nerve-activated vestibulospinal neurons descended through the contralateral vestibulospinal tracts terminating in the upper cervical segments. Most of the saccular nerve-activated vestibulospinal neurons originated in the caudal part of the lateral nucleus and rostral part of the descending nucleus.

Notes: Abstract  The aim of this investigation was to understand the functions of long horizontal connections projecting from area 17 to area 18 in cats. The animals were anesthetized and prepared for recording single-cell responses to sine-wave gratings in area 18. Neuronal activity was analyzed under three conditions: prior to, during, and after inactivation of a circumscribed region of area 17. The latter was depressed with micro-injections of GABA. Cells in both areas were in close retinotopic correspondence. Cells were classified as simple and complex types. Globally, simple cells were less affected than complex units, and those which were affected shifted their optimal spatial frequency to higher values. Complex neurons were more often influenced by the interruption of area 17 input. Namely, the peaks of the tuning curves were displaced on the x-axis to a new optimal spatial frequency. This effect was obtained by a dual change: a decline in the discharge strength to the optimal spatial frequency and an enhancement to nonoptimal spatial frequency. Contrast sensitivity function disclosed similar shifts of optimal spatial frequencies. Likewise bandwith, spatial resolution, high cutoff, and low cutoff were modified to a greater extent in complex cells. It appears that there is no relationship between areas 17/18 orientation difference and the modifications observed in tuning curves to spatial frequencies. The results suggest that neurons of area 18 may carry multiple-frequency channels and that area 17 facilitates the emergence of one particular spatial frequency.

Notes: Abstract  In the lumbar ventral horn of pentobarbitone-anaesthetised cats, (-)-baclofen reduces both the synaptic release of excitatory transmitter from muscle group Ia afferent terminations and the duration of the presynaptic action potentials of these terminations, presumably by interfering with the influx of calcium ions through voltage-activated channels. Baclofen, however, has little or no effect on cholinergic excitation at motor axon collateral synapses on spinal Renshaw cells and, in the present study, was found not to reduce the duration of the action potential of axon collateral terminations located in the vicinity of Renshaw cells in pentobarbitone-anaesthetised cats. Furthermore, in contrast to group Ia terminations, a 4-aminopyridine-sensitive potassium conductance could not be detected as contributing to axon collateral termination action potentials. These results suggest that there may be differences in presynaptic ion fluxes associated with transmitter release at the intraspinal terminations of group Ia afferent fibres and motor axon collaterals in the cat spinal cord.

Notes: Abstract  The effect of exposure to repeated angular velocity steps about the earth-vertical axis on the vertical vestibulo-ocular reflex (VOR) during onside pitch rotation was investigated in normal cats. By contrast with the VOR in the horizontal plane, the amplitude and duration of the vertical VOR did not progressively decrease throughout the repetition of velocity steps alternated in both directions. Instead, the amplitude of VOR decreased by about 40% during the very first trials in naive cats and then stayed unchanged with repeated stimuli. Habituation of the amplitude of the vertical VOR was observed when the velocity steps were always directed in the same direction. However, the duration of the vertical VOR did not show any signs of habituation. The habituation of the amplitude of the vertical VOR during unidirectional training was due to the progressive development of an initial inhibition of the VOR. This initial inhibition appeared much earlier during the bidirectional protocol, and was presumably responsible for the larger reduction in VOR amplitude observed during the very first session. These results support the model of two distinct mechanisms for VOR habituation, one producing an increasing inhibition of nystagmus, and the other depressing the response duration, and suggest that only the first mechanism is generated during repeated stimulation in the vertical plane. The low-frequency information provided by the velocity storage mechanism during onside pitch rotation, when the otoliths are positioned so they do not signal head tilt relative to gravity, could prevent a decrease in the overall response by the second mechanism.

Notes: Abstract  Neurophysiological studies of the blink reflex to supraorbital nerve stimulation were conducted in eight alert, adult male cats. The cat, like other mammals, shows both short-latency (R1) and long-latency (R2) orbicularis oculi electromyographic (OOemg) components. Measures of OOemg latency, duration, integrated area, and maximum amplitude (MA) were obtained at a stimulus magnitude of 1.5×R2 threshold. The mean (±SE) minimal latencies for R1 and R2 were 8.26±0.85 and 22.97±1.53 ms, respectively. On average, R1 MA was larger than R2 MA. R1 and R2 area measures were similar. Three stimulus paradigms were tested. In a paired-stimulus paradigm, the interstimulus interval (ISI) was randomly varied from 100 to 1200 ms. Ratios were constructed for the OOemg area and MA by dividing the test response by the conditioning response. In this paradigm, although a significant linear relationship was observed only between ISI and R2 MA, conditioning effects were noted on both R1 and R2 area and MA test responses at several ISIs. In a habituation paradigm, both R2 and R1 showed habituation at stimulus frequencies from 0.5 to 2 Hz. In a stimulus-response paradigm, stimulus magnitude was randomly varied between threshold and 2×threshold. In this paradigm, OOemg area and MA of both R1 and R2 were linearly related to stimulus magnitude. Neither the systemically administered centrally acting α2-adrenergic antagonist yohimbine nor agonist clonidine had significant effects on blink reflex parameters, habituation, or the paired-stimulus paradigm. Overall, these results suggest that there are important similarities in the control and modulation of the R1 and R2 components of the blink reflex to supraorbital nerve stimulation in cats.

Notes: Abstract  Somaesthetic input to rubrospinal cells, bypassing the cerebellum and cerebral cortex, has been demonstrated in the cat. The detailed organization of this somatic afferent system was studied using electrophysiological methods on multiple-lesion, chloralose-anaesthetized preparations. Stimulation of the dorsal column (DC) at upper cervical cord segments induced significant responses in magnocellular red nucleus (RNm) cells in cats without a cerebellum and with ablation of the frontal cortex. As classic descriptions state that primary afferents fibres have ascending and descending branches in the DC, with many collaterals arborizing in the grey matter at the segmental level of the cord, this procedure is equivalent to stimulating the somatic fibres coming from a large portion of the body, leading to the simultaneous activation of most ascending spinal pathways. To show that the pathway responsible for the rubral responses ascends in the ventral spinal cord, and that the synaptic relays are located at the segmental level, the stimulation was applied to the DC, caudally to the sectioned dorsal spinal half. Various tests confirmed that the activation was conducted to rubral cells through antidromically activated primary afferents. Their multiple collaterals relay the messages to cells located caudal to the spinal lesion, with fibres ascending in the ventral cord. Any relay of the somatic rubral responses in the DC’s nuclei was excluded. When the DC was sectioned and its rostral end was dissected free and lifted onto two hook electrodes for stimulation, no response was obtained in the rubral cells. This dissection indeed sectioned all DC fibre collaterals entering the grey matter, thus excluding the possibility of segmental relay. Single shocks applied to the ventral quadrant of the cord or in the medial lemniscus (LM) in the medulla oblongata induced monosynaptic excitatory post-synaptic potentials (EPSPs) in most rubrospinal cells. The spinal EPSPs could be collided by stimulation in the LM, thus demonstrating the existence of direct connections from the cord to the RNm. This somaesthetic pathway to the RNm could be involved in on-line correction of movements and in learning new motor strategies.

Notes: Abstract. We investigated the binding characteristics of two monoclonal antibodies, 4F3 and 3F8, which in the retina specifically stain Müller cells, both with protein blots and immunohistochemically in sections of various regions of the central nervous system of neonatal and adult cats and rats. Clear differences emerged between the two antibodies. In addition, some species-specific as well as developmental differences within the staining pattern of each individual antibody were evident. The epitopes recognized by 4F3 lay mainly in the 57–63 kDa range. Histologically, 4F3 labelled mainly glia cells: oligodendrocytes and astrocytes in optic nerve, astrocytes in neocortex and cerebellum, Bergmann glia in the cerebellum and radial glia in neonatal animals. This was confirmed by double-immunofluorescence with the astrocyte marker GFAP. By contrast, 3F8 epitopes lay mainly in the 47–49 kDa range. Histologically, 3F8 labelled oligodendrocytes in the optic nerve, but only neurons in cerebellum and neocortex as confirmed by double-labelling with neuronal markers. Neither 4F3 nor 3F8 recognized GFAP or vimentin. These results clearly indicate (1) that the two antibodies identify new epitopes/molecules, (2) that the antigens are not retina-specific, and (3) that Müller cells share epitopes with other glial cells as well as with neurons outside the retina.

Notes: Two new enantioselective syntheses of the naphthopyranquinone antibiotic frenolicin B (1), of its enantiomer 2, and of its diastereoisomers 3 and 4 were accomplished using two different routes from optically active β-Hydroxy esters (R)- and (S)-11 and 18. β-Hydroxy esters (R)- and (S)-11 were prepared stereoselectively from optically active sulfenylacetates (S)- and (R)-10, respectively (Scheme 2, Method A). Alternatively, compound 18 was obtained in excellent yield by enantioselective hydrogenation of the corresponding β-keto ester 17, using a chiral ruthenium-complex catalyst (Scheme 3, Method B). Subsequently, compounds (S)-11 and 18 were transformed into frenolicin B (1). In analogy, Stereoisomers 2-4 were prepared from (S)- and (R)-11 in good yields.

Notes: The 2′-deoxyisoguanosine phosphonates 3a and 4a and the phosphoramidites 3b and 4b were prepared as building blocks for solid-phase oligonucleotide synthesis. The diphenylcarbamoyl (dpc) residue was introduced as 2-oxo protecting group which stabilizes the N-glycosylic bond against hydrolysis and prevents the molecule from side reactions. The dpc-protected building blocks 4a, b were employed in solid-phase synthesis and were found to be much more efficient than the unprotected compounds 3a, b. Oligonucleotides with alternating (11) or consecutive isoguanine residues (13-15) were synthesized. They form duplexes with parallel chain orientation. The aggregate d(T4-iG4-T4) (15) containing four consecutive 2′-deoxyisoguanosine is shown to be a tetramer similar to that of d(T4-G4-T4).

Notes: Khusimone (1), one of the main odor-donating compounds of vetiver oil is subject of the following study on structure/odor relationship. The omittance of the ethano bridge of the tricyclic khusimone leads to a bicyclic system. The stereoselective approach to this degraded structure is described, and the olfactory properties are studied. The key step of the synthesis of the hydrindane nucleus is based on a highly diastereoselective conjugate addition to a chiral oxo-cyclopentene-2-carboxylate.

Notes: The (2-dansylethoxy)carbonyl (= {2-{[5-(dimethylamino)naphthalen-l-yl]sulfonyl}ethoxy}carbonyl; dnseoc) group was employed for protection of the amino functions of the aglycone residues. The lactam function of 2′-deoxyguanosine was on the one hand unprotected and on the other hand alkylated at O6 of the aglycone with the 2-(4-nitrophenyl)ethyl (npe) and 2-(phenylsulfonyl)ethyl (pse) group, respectively. The syntheses of monomeric building blocks, both phosphoramidites and nucleoside- functionalized supports, are described for the three common 2′-deoxynucleosides (2′-deoxycytidine, 2′-deoxyadenosine, 2′-deoxyguanosine). As kinetic studies with the tritylated nucleosides showed, the dnseoc group is more labile towards DBU cleavage than the corresponding 2-(4-nitrophenyl)ethyl-(npe) and [2-(4-nitrophenyl)ethoxy]carbonyl(npeoc)-protected analogues (see Table 2). These results were confirmed by the very fast deprotection rate of the dnseoc groups at some oligonucleotides.

Notes: The absolute configuration of 3-methylpyrrolidine alkaloids isolated from the poison gland of ants Leptothoracini was determined as (3R). The enantiomeric separation by chiral gas chromatography and unambiguous structural assignment of the target compounds are described.

Notes: The synthesis of π-substituted heptalenecarboxylates or -dicarboxylates, starting with the easily available dimethyl 9-isopropyl-1, 6-dimethylheptalene-4, 5-dicarboxylate (2b), are described. Treatment of 2b with t-BuOK and C2Cl6 at -78° leads to the chemoselective introduction of a Cl substituent in Me-C(1) (see 5b in Scheme 1). Formation of the corresponding triphenylphosphonium salt 7b via the iodide 6b (Scheme 2) allowed a Wittig reaction with cinnamaldehyde in the two-phase system CH2Cl2/2N NaOH. Transformation of the 4, 5-dicar-boxylate of 2b into the corresponding pseudo-ester 10b allowed the selective reduction of the carbonyl function at C(4) with DIBAH to yield the corresponding 4-carbaldehyde 11b (Scheme 3). Wittig reaction of 11b with (benzyl) triphenylphosphonium bromide led to the introduction of the 4-phenylbuta-1, 3-dienyl substituent at C(4). The combination of both Wittig reactions led to the synthesis of the 1, 4-bis(4-phenylbuta-1, 3-dienyl)-substituted heptalene-5-carboxylate (all-E)-17b (Scheme 5). In a similar manner, by applying a Horner-Wadsworth-Emmons reaction, followed by the Wittig reaction, the donor-acceptor substituted heptalene-5-carboxylate (E;E)-22b was synthesized (Scheme7). Most of these new heptalenes are in solution, at room temperature, in thermal equilibrium with their double-bond shifted (DBS) isomers. In the case of (all-E)-17b and (E;E)-22b, irradiation of the thermal equilibrium mixture with light of λ -(439 ± 10) nm led to a strong preponderance ( 〉 90%) of the DBS isomers 17a and (E;E)-22a, respectively (Schemes 6 and 7). Heating of the photo-mixtures at 40° re-established quickly the thermal equilibrium mixtures. Heptalenes-carboxylates (all-E)-17a and (E;E)-22a which represent the off-state of a 1,4-conjugative switch (CS) system show typical heptalene UV/VIS spectra with a bathochromically shifted heptalene band III and comparably weak heptalene bands II and I which appear only as shoulders (Figs. 4 and 5). In contrast, the DBS isomers (all-E)-17b and (all-E)-22b, equivalent to the on-state of a 1,4-CS system, exhibit extremely intense heptalene bands I and, possibly, II which appear as a broad absorption band at 440 and 445 nm, respectively, thus indicating that the CSs (all-E)-17a⇌(all-E)-17b and (E;E)-22a⇌(E;E)-22b are perfectly working.

Notes: Configurational and Conformational Isomeric Antiaromatic [28]Tetraoxaporphyrinoids(4.2.4.2) and Aromatic [26]Tetraoxaporphyrin(4.2.4.2) Dications. A New Type of Molecular Dynamics in Macrocyclic SystemsThe [28]tetraoxaporphyrinoids(4.2.4.2) 6 are synthesized by cyclizing Wittig reaction of (E, E)-5, 5′-(buta-1, 3-diene-1, 4-diyl)bis[furan-2-carbaldehyde] (8) with (E, E)-{(buta-1, 3-diene-diyl)bis[(furan-5, 2-diyl)methylene]}bis-[triphenylphosphonium] dibromide (9) and 3, 3′-{[(E)-ethene-1, 2-diyl]bis(furan-5, 2-diyl)}bis[(E)-prop-2-enal] (22) with (E)-{(ethene-1, 2-diyl)bis[(furan-5.2- diy)methylene]}bis[triphenylphosphonium] dibromide (23). An alternative path to get 6 is the McMurry condensation of 8. Four different configurational isomers of 6 could be isolated and characterized by 1H-NMR spectroscopy. The (Z, EE, Z, EE)-isomer 6a is the first macrocyclic system where the inner and outer protons of the (E, E)-dienediyl bridges exchange by rotation around the adjacent single bonds. In the (Z, EE, E, EE)-isomer 6b, the (E)-ethenediyl bridge is rotationally active, while in the (E, ZE, E, EZ)-isomer 6c and in the (E, EZ, E, EZ)-isomer 6e, the rotation of both (E)-ethenediyl bridges is observed. When in the dynamic systems the rotation of the active (E)-double bonds at temperatures T 〈 -90° is frozen, all configurational isomers of 6 appear to be antiaromatic and paratropic. The oxidation of the [28]tetraoxaporphyrinoids 6c and 6e with DDQ yields the aromatic, diatropic [26]tetraoxaporphyrin(4.2.4.2) dications 21e/21e′ both with (E, EZ, E, EZ)-configuration but different fixed conformations. (Z, EE, Z, EE)-Isomer 6a is oxidized to give the (Z, EE, Z, EE)-dication 21a, while the oxidation of 6b yields a mixture of 21a and 21e/21e′. The standard formation enthalpies of the obtained and expected [28]tetraoxaporphyrinoids 6 and [26]tetraoxaporphyrin dications 21 have been calculated with the AM1 method, showing good accordance with the experimental results.

Notes: The synthesis of substituted cyclododeca-1,6-diallenes.( = cyclododeca-1,2,6,7-tetraenes) from cyclododeca-5,11-diyne-1,4-diols is described (Schemes 1 and 3). The ca. 1:1 mixtures of the stereoisomers of the cyclododeca-1,6-diallenes were formed in high yields from the ca. 1:1 diastereoisomer mixtures of the 1,4-disubstituted cyclododeca-5,11-diynes by reactions with Me2CuLi or t-BuMgCl/CuII. In mechanistically relevant experiments with the pure diastereoisomers of 1,4-dimethylcyclododeca-5,11-diyne-1,4-diol, it is demonstrated that the configuration is conserved in these reactions. The first synthesis of a 1-substituted cyclododeca-2,8-diyne bearing only one propargylic leaving group gives access to a mixed 12-membered allen-yne (Scheme 5).

Notes: This study was designed to unravel lipophilicity changes associated with the oxidation state of the S-atom in model compounds, drugs, and metabolites, special attention being given both to intermolecular and intramolecular effects. The methods used were experimental (potentiometry, CPC, and shake-flask techniques to measure lipophilicity, 13C-NMR spectroscopy to investigate tautomeric equilibria) and computational (quenched molecular dynamics and molecular lipophilicity potential). Simple, monofunctional model compounds were used to assess intermolecular forces, as revealed by the Δlog Poct-alk and Δlog Poct-chf parameters. Drugs and their metabolites proved to be good probes to study intramolecular effects in both neutral and anionic forms, as revealed by the difference between calculated and experimental log Poct values (the diff(log Pexp-calc) parameter). Sulindac and its metabolites showed a normal partitioning behavior, whereas the lipophilicity of sulfmpyrazone and its metabolites' was markedly affected by tautomeric and conformational equilibria.

Notes: The synthesis of (E)-hex-3-ene-l, 5-diynes and 3-methylidenepenta-1, 4-diynes with pendant methano[60]-fullerene moieties as precursors to C60-substituted poly(triacetylenes) (PTAs, Fig. 1) and expanded radialenes (Fig. 2) is described. The Bingel reaction of diethyl (E)-2, 3-dialkynylbut-2-ene-1, 4-diyl bis(2-bromopropane-dioates) 5 and 6 with two C60 molecules (Scheme 2) afforded the monomeric, silyl-protected PTA precursors 9 and 10 which, however, could not be effectively desilylated (Scheme 4). Also formed during the synthesis of 9 and 10, as well as during the reaction of C60 with thedesilylated analogue 16 (Scheme 5), were the macrocyclic products 11, 12, and 17, respectively, resulting from double Bingel addition to one C-sphere. Rigorous analysis revealed that this novel macrocyclization reaction proceeds with complete regio- and diastereoselectivity. The second approach to a suitable PTA monomer attempted N, N′-dicyclohexylcarbodiimide(DCC)-mediated esterification of (E)-2, 3-diethynylbut-2-ene-l, 4-diol (18, Scheme 6) with mono-esterified methanofullerene-dicarboxylic acid 23; however, this synthesis yielded only the corresponding decarboxylated methanofullerene-carboxylic ester 27 (Scheme 7). To prevent decarboxylation, a spacer was inserted between the reacting carboxylic-acid moiety and the methane C-atom in carboxymethyl ethyl 1, 2-methano[60]fullerene-61, 61-dicarboxylate (28, Scheme 8), and DCC-mediated esterification with diol 18 afforded PTA monomer 32 in good yield. The formation of a suitable monomeric precursor 38 to C60-substituted expanded radialenes was achieved in 5 steps starting from dihydroxyacetone (Schemes 9 and 10), with the final step consisting of the DCC-mediated esterification of 28 with 2-[1-ethynyl(prop-2-ynylidene)]propane-1, 3-diol (33). The first mixed C60-C70 fullerene derivative 49, consisting of two methano[60]fullerenes attached to a methano[70]fullerene, was also prepared and fully characterized (Scheme 13). The Cs-symmetrical hybrid compound was obtained by DCC-mediated esterification of bis[2-(2-hydroxy-ethoxy)ethyl] 1, 2-methano[70]fullerene-71, 71-dicarboxylate (46) with an excess of the C60-carboxylic acid 28. The presence of two different fullerenes in the same molecule was reflected by its UV/VIS spectrum, which displayed the characteristic absorption bands of both the C70 and C60 mono-adducts, but at the same time indicated no electronic interaction between the different fullerene moieties. Cyclic voltammetry showed two reversible reduction steps for 49, and comparison with the corresponding C70 and C60 mono-adducts 46 and 30 indicated that the three fullerenes in the composite fullerene compound behave as independent redox centers.

Notes: By the tether-directed remote functionalization method, a series of bis- to hexakis-adducts of C60, i.e., 1-7 (Fig. 1), had previously been prepared with high regioselectivity. An efficient method for the removal of the tether-reactive-group conjugate was now developed and its utility demonstrated in the regioselective synthesis of bis- to tetrakis(methano)fullerenes ( = di- to tetracyclopropafullerenes-C60-Ih) 9-11 starting from 4, 5, and 7, respectively (Schemes 2, 4, and 5). This versatile protocol consists of a 1O2 ene reaction with the two cyclohexene rings in the starting materials, reduction of the formed mixture of isomeric allylic hydroperoxides to the corresponding alcohols, acid-promoted elimination of H2O to cyclohexa-1,3-dienes, Diels-Alder addition of dimethyl acetylenedicarboxylate, retro-Diels-Alder addition, and, ultimately, transesterification. In the series 9-11, all methano moieties are attached along an equatorial belt of the fullerene. Starting from C2v-symmetrical tetrakis-adduct 15, transesterification with dodecan-1-ol or octan-1-ol yielded the octaesters 16 and 17, respectively, as noncrystalline fullerene derivatives (Scheme 3). The X-ray crystal structure of a CHCl3 solvate of 11 (Fig. 3) showed that the residual conjugated π-chromophore of the C-sphere is reduced to two tetrabenzopyracylene substructures connected by four biphenyl-type bonds (Fig. 5). In the eight six-membered rings surrounding the two pyracylene (= cyclopent[fg]acenaphthylene) moieties, 6-6 and 6-5 bond-length alteration (0.05 Å) was reduced by ca. 0.01 Å as compared to the free C60 skeleton (0.06 Å) (Fig. 4). The crystal packing (Fig. 6) revealed short contacts between Cl-atoms of the solvent molecule and sp2- and sp3-C-atoms of the C-sphere, as well as short contacts between Cl-atoms and O-atoms of the EtOOC groups attached to the methano moieties of 11. The physical properties and chemical reactivity of compounds 1-11 were comprehensively investigated as a function of degree and pattern of addition and the nature of the addends. Methods applied to this study were UV/VIS (Figs. 7-11), IR, and NMR spectroscopy (Table 2), cyclic (CV) and steady-state (SSV) voltammetry (Table 1), calculations of the energies of the lowest uunoccupied mmolecular orbitals (LUMOs) and electron affinities (Figs. 12 and 13), and evaluation of chemical reactivity in competition experiments. It was found that the properties of the fullerene derivatives were not only affected by the degree and pattern of addition but also, in a remarkable way, by the nature of the addends (methano vs. but-2-ene-1, 4-diyl) anellated to the C-sphere. Attachment of multiple thano moieties along an equatorial belt as in the series 8-11 induces only a small perturbation of the original fullerene π-chromophore. In general, with increasing attenuation of the conjugated fullerene π-chromophore, the optical (HOMO-LUMO) gap in the UV/VIS spectrum is shifted to higher energy, the number of reversible one-electron reductions decreases, and the first reduction potential becomes increasingly negative, the computed LUMO energy increases and the electron affinity decreases, and the reactivity of the fullerene towards nucleophiles and carbenes and as dienophile in cycloadditions decreases.

Notes: Crystal and solution structures of the enantiomerically pure and the racemic pairs of (η3-allyl) {2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-phenyloxazole}palladium(II) hexafluorophosphates (1, and rac-1, resp.) and tetraphenylborates (2, and rac-2, resp.) as well as (η3-allyl){2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-isopropyloxazole}palladium(II) tetraphenylborate (3) were characterized by X-ray crystallography and 1H-NMR spectroscopy. In the solid state, rac-1 and rac-2 proved to be disordered with both diastereoisomeric complexes in the crystal. The complexes 2 and 3 exist only in the ‘exo’ form. The X-ray structures show that the [PdII(η3-allyl)] moiety may adopt different configurations between a nearly symmetrical three-electron PdII(π3-allyl) system and an asymmetrical allyl group with a η1- and a η2-bonding to the metal center. The [PdII(η3-allyl)] system of rac-1 and of ‘endo’ rac-2 is closer to the former, and that of 2, ‘exo’-rac-2, and 3 closer to the later geometry. The 1H-NMR spectra of the hexafluorophosphates 1 and rac-1 show two sets of signals of the allylic protons in an ‘exo’/‘endo’ ratio of 2:3. The tetraphenylborates 2, rac-2, and 3 give only one set of broad signals of the allylic protons.

Notes: ‘Acetyleno-oligosaccharides’ in which two terminal ethynyl substituents enclose an angle (significantly) below 180° are building blocks for the preparation of cyclodextrin analogues. This is illustrated by the preparation of a cyclotrimer and a cyclotetramer; the C3-symmetrical cyclotrimer 18 (Scheme 1) was synthesized in 13 steps (7.7%) and the C4-symmetrical cyclotetramer 51 (Scheme 3) in 14 steps (4.3%) from the known dialkyne 21. The solubilities of 18 and 51 in H2O were determined by gravimetry; a saturated solution is 130 mM in the trimer 18 and 12.8 mM in the tetramer 51. The dependence of the optical rotation of 18 and 51 in H2O on the concentration, and the concentration dependence of the 1H-NMR chemical shift of the signals of the 1CH groups of 51 (D2O) suggest that there is no significant self-association of 18 and 51.

Notes: The chiral biyclic bis-lactams of structures 3 and 4 were synthesized from the key intermediate 2′b, the N,N′-bis(4-methoxybenzyl) derivative of 2 (X = MeO) (Scheme 6). The synthesis of this intermediate involved two key steps: (1) a double condensation of glyoxylic acid/anisamide (= oxoacetic acid/4-methoxybenzamide) adduct 11c with veratrole (1,2-dimethoxybenzene; 10) allowed the introduction of two glycine units at the 4,5-positions of the veratrole ring to give 18c (Schemes 3 and 4); (2) in order to circumvent the hydrolysis of 4-methoxybenzoyl protective groups which proved to be unfeasible, these groups were transformed into 4-methoxybenzyl groups through a sequence involving thiocarbonylation followed by reduction (Scheme 5). Thereafter, the double intramolecular cyclization of the resulting diamino diester 22c proceeded easily to afford 2′b. This intermediate may be transformed via the tetrol 2′g or the diol 2′h into the N-protected derivatives of 2 (X = OR) and of 3 (X = OCOR). Cleavage of the 4-alkuxybenzyl groups was achieved by ceric ammonium nitrate. However, when the aromatic ring bore ether functions (N-protected 2), this normal reaction was accompanied by the oxidative ring cleavage to give the diene-diester structure 4 (Schemes 5 and 6).

Notes: The kinetics of the Cu2+ complexation by macrocycles 1 (4-[(l,4,8,11-tetraazacyclotetradec-1-yl)methyl]-benzoic acid) and 2 (N-propyl-4-[(1,4,8,11-tetraazacyclotetradec-1-yl)methyl]-benzamide) as well as by macrocycle 1 conjugated to bovine serum albumin (bsa) and to ribonuclease A (rnase) were studied by stopped flow techniques. For 1 and 2, the kinetics were followed in the mM range monitoring the d-d* absorption band of the Cu2+ complex. From the pH dependence of kobs, the rate law is v = [Cu2+] (kLH[LH] + kLH2[LH2]), where kLH and kLK2 are the bimolecular rate constants for Cu2+ with the diprotonated (LH2) and monoprotonated (LH1) form of the ligand, respectively. The values are kLH2 = 1.7(1) M-1s-1 and kLH = 2.3(1) 105 M-1s-1 for 1, and kLH2, = 0.28(9) M-1s-1 and kLH = 2.0(1) 105 M-1s-1 for 2. The kinetics of the Cu2+ incorporation into 1,2 and 1 conjugated to bsa and rnase, i.e., 3 and 4, respectively, were also followed using nitroso-R salt as a metal indicator in the μM range, i.e., under conditions typical for the ‘post-labeling’ technique to give radiolabeled monoclonal antibodies. In these cases, the reaction takes place between the 1:1 complex of Cu2+ with nitroso-R-salt and the macrocycle. At pH 6.5, the rates are very similar to each other indicating that the complexation properties of the macrocycle attached to a protein are not very different from those of the free ligand under comparable conditions.

Notes: The synthesis of a variety of hydroxylactams from ω-phthalimidoalkanoates using a triplet-sensitized photodecarboxylation reaction initiated by intramolecular photo electron transfer is described. Ring sizes available by this method span from 4 (benzazepine-1,5-dione 7) to 26 (cyclodipeptide 26e). Ground-state template formation is proposed as the explanation for the high efficiency of this reaction and for the decrease in reactivity in the presence of organic bases instead of metal carbonates. The crucial step in this macrocyclization reaction seems to be the protonation of the intermediary ketyl radials (Scheme 4). Spacer groups investigated were alkyl chains (C3-C11: 5c-h, 11a, 12), ether (16, 18), ester (20, 22), and amide (26a-f) linkages. Within the detection limits, no dimeric (= decarboxylative coupling) products were observed, indicating the high preference for intra-vs. intermolecular photoelectron transfer. The C,C radical combination step proceeds with low stereoselectivity (cf, products 11 and 12) in contrast to comparable singlet reactions. Except for the lactones 22, all products were stable under the photolysis conditions. Prolonged irradiation of 22 led to the formation of the spiro compounds 23, probably via an intermediary acyliminium betaine (Scheme 8). One serious limitation of the decarboxylative macrocyclization is its incompatibility with the glycine spacer (as in 27a and 27b), probably the consequence of a strong intramolecular H-bond (Scheme 10).

Notes: A novel tricyclic dipeptide template, formally derived by coupling (2S,4S)-4-aminoproline (Pro(NH2)) and (S)-2-(carboxymethyl)proline (Pro(CH2COOH)) as a diketopiperazine, has been synthesized in a form suitable for solid-phase peptide synthesis using Fmoc chemistry. This template was incorporated into the cyclic molecule cyclo(-Ala1-Asn2-Pro3-Asn4-Ala5-Ala6-Temp-) (Temp = template), whose conformation in H2O was studied by NMR methods. Average solution structures derived by restrained simulated annealing point to a highly populated βI-turn within the Asn-Pro-Asn-Ala motif and also indicate which conformations are likely to be preferred by the template.

Notes: The syntheses of both diastereoisomers of 5′-ethyl-substituted thymidine dimers, the (5′R)- and (5′S)-configurated 33a and 33b respectively, in which the natural phosphodiester linkage is replaced by an amide group (C(3′)-CH2CONH-CH(5′)(Et)), arc described. Their fully protected derivatives 35a and 35b, respectively, are suitable for incorporation into antisense oligonucleotides. Unexpectedly, an attempted PdII-catalysed aza-Claisen rearrangement of trichloroacetimidate 7 provided the diastereoisomerically pure cyclopropane derivative 17, whose structure was confirmed by X-ray analysis.

Notes: New Pathways to Precursors of PentalenePentalene dimers 2 and 3 are easily available in moderate yields by CuCl2-induced oxidative coupling of dilithium-pentalenediide (5) (Scheme 1). On the other hand, NBS bromination of 1,5-dihydropentalene (4) or of 1,2-dihydropentalene (8) gives unstable 1-bromo-1,2-dihydropentalene (9), while subsequent in-situ elimination with Et3N exclusively gives syn-cis-pentalene dimer 2 in moderate yields (Scheme 3). NMR-Spectroscopic evidence for compounds 2, 3, and 9 is presented, and mechanistic alternatives for the formation of pentalene dimers 2 and 3 are discussed.

Notes: Four new iridoid glucosides 1-4, named blumeosides A-D, were isolated from the methanolic stem-bark extract of Fagraea blumei G. DON. (Loganiaceae). They were accompanied by the benzyl-alcohol derivative di-O-methylcrenatin (5) and the flavone C-glucoside swertisin (6). The structures of 1-4 were established by spectroscopic methods, including FAB-MS, and 1H- and 13C-NMR, and by alkaline hydrolysis. Blumeosides A (1) and C (3) are 10-O-(2,5-dihydroxytercphthalo) adoxosidic acid and 10-O-(2-hydroxyterephthalo)adoxosidic acid, respectively. In blumeosides B (4) and D (2), both carboxylic groups of the terephthalic-acid moiety are esterified by adoxosidic-acid units, Blumeosides A-D (1-4) inhibited bleaching of crocin induced by alkoxyl radicals. Blumeosides A (1) and D (2) also demonstrated scavenging properties towards the 2,2-diphenyl-1-picryl-hvdrazvl (CDPPH) radical in TLC autographic and spectrophotometric assays.

Notes: The kinetic model of column chromatography is revisited to explicitly show that this approach yields, when neglecting axial dispersion, a rather simple analytical expression depending only on two dimensionless parameters, namely a dimensionless kinetic retention parameter and a dimensionless time parameter. An expression for the time corresponding to the maximum of the peak is also proposed.

Notes: The αv/β3 integrin is implicated in human tumor metastasis and angiogenesis. It has been shown that structures of the sequence cyclo(-Arg1-Gly2-Asp3-D-Phe4-Xaa5-) (I) and cyclo(-Arg1-Gly2-Asp3-Phe4-D-Xaa5-) (II) bind with high affinity and the latter with high selectivity to this receptor. The residues Xaa and D-Xaa accept a broad variety of amino acids. Here, we report on the synthesis, activities, and conformational analysis of cyclic Arg-Gly-Asp (RGD) peptides containing liophilic amino acids Xaa or D-Xaa in position 5. For I, these were (2S)-2-aminohexadecanoic acid (Ahd) and N′-hexadecylglycine (Hd-Gly) and in II, D-Ahd and Hd-Gly, and, for control purposes, Ahd were incorporated (Fig. 1). The enantiomerically pure a-amino acids were obtained by non-enantioselective synthesis and subsequent enzymatic separation of isomers using acylase I (Scheme). Hd-Gly was prepared in a modified procedure according to Stewart from ethyl bromoacetate and hexadecylamine (Scheme). The synthesis and physicochemical properties of the corresponding (9H-fluoren-9-ylmethoxy)carbonyl (Fmoc) derivatives, compatible with solid-phase peptide synthesis, are described. Structure elucidation by NMR reveals that the lipid modification has no significant impact on the template structures when incorporated into them. For peptides I with Xaa = Ahd or Hd-Gly (1 or 2), a βII′/γ-turn-like arrangement with D-Phe in i+1 position of the β-turn is found. Peptides II with D-Xaa = D-Ahd or Hd-Gly (3 or 4) exhibit a βII′/γ-turn conformation with Gly in i+1 position of the β-turn, whereas II with Ahd instead of D-Xaa, i.e., lacking a D-amino acid in position 4 or 5 (5). adopts no defined conformation. However, in assays of receptor specificity employing human αvv/β3 integrin, the compounds exhibit IC50 values ranging from nanomolar to less than millimolar. These results indicate that although the arrangement of the pharmacophoric groups is preserved in the target compounds, the biological activity is highly dependent on spatial requirements of the lipid anchor in the receptor binding pocket. Obviously, only certain positions do not affect the binding.

Notes: The conformational analysis of naturally occurring cytostatic cyclic heptapeptides axinastatin 2, 3, and 4 was carried out by two-dimensional NMR spectroscopy in combination with distance-geometry (DG) and molecular-dynamics (MD) calculations in explicit solvents. The synthesized secondary metabolites were examined in (D6)DMSO. Axinastatin 2 was also investigated in CD3OH. In all structures, Pro2 is in the i + 1 position of a βI turn and Pro6 occupies the i + 2 position of a βVIa turn about the cis amide bond between residue 5 and Pro6. In all peptides, a bifurcated H-bond occurs between residue 4 CO and the amide protons of residue 1 and 7. For axinastatin 2 and 3, an Asn Ig turn was found about Asn1 and Pro2. We compared these structures with conformations of cyclic heptapeptides obtained by X-ray and NMR studies. A β-bulge motif with two β turns and one bifurcated H-bond is found as the dominating backbone conformation of cyclic all-L-heptapeptides. Axinastatin 2, 3, and 4 can be characterized by six trans and one cis amide bond resulting in a β/βVI(a)-turn motif, a conformation found for many cyclic heptapeptides. Detailed biological tests of the synthetic compounds in different human cancer cell lines indicates these axinastatins to be inactive or of low activity.

Notes: In the presence of activating agents, the N-acylglycine 8 reacts with electrophilic alkynes via the münchnone9 to the pyrrolopyridines (= indolizines) 10, 18, and 19 (Scheme 1 ), Depending on the nature of the activating agent and the reaction temperature, the formation of the pyrroles was accompanied by partial epimerization to the manna-configurated epimers 16 and 17. The gluco-configurated pyrrolopyridine 10 was deprotected to 12. Silylation of 12, followed by reduction and desilylation, gave the hexol 15. Cycloaddition of 9 to 4-toluenesulfonyl cyanide yielded 53% of the imidazole 23, while cycloaddition to phenyl cyanate gave the phenoxyimidazole 28 in low yields only (Scheme 2). As expected, the deprotected pyrroles 12, 15, 20, and 21 are weak inhibitors of retaining β-glucosidases, while the deprotected imidazole 24 derived from 23 proved a good inhibitor of sweet-almond β-glucosidases and a powerful inhibitor of Caldocellum saccharolyticum β-glucosidase.

Notes: Tetrahydrobenzo[a]pyrrolizidines (= octahydro-1H-pyrrolo[2,1-a]isoindoles) and tetrahydrobenzo[a]indo-lizidines, (= decahydropyrido[2,1-a]isoindoles) were prepared stereoselectively in four steps through an amineinduced ring-opening of 3-bromo-2,5-dimethylthiophene 1,1-dioxide (1) with L-prolinol (9), piperidine-2-methanol (10), and piperidine-2-ethanol (11), yielding the dienes (2S)-1-[(2E,4Z)-4-bromohexa-2,4-dienyl]pyrrolidine-2-methanol (12), 1-[(2E,4Z)-4-bromohexa-2,4-dienyl]piperidine-2-methanol (13), and 1-[(2E,4Z)-4-bromo-hexa-2,4-dienyl]piperidine-2-ethanol (14; Scheme2), which, after conversion into their α,β-unsaturated esters, cyclized in a TiCl4-catalyzed intramolecular Diets-Alder reaction (Scheme3). A discussion on the mechanism of the ring opening reaction including semiempirical and ab initio calculations is also presented.

Notes: The X-ray crystal-structure analyses of two N-enoyl-toluenesultam derivatives 1 are reported. The structural differences with their bornanesultam analogues 2 as well as stereochemical aspects with respect to their [4 + 2] and [3 + 2] cycloadditions are discussed.

Notes: Boophiline (1), a new sterol amide was isolated from the cattle tick Boophilus microplus (Ixodidae). The structure was assigned as N-[3-(sulfooxy)-25ξcholest-5-en-26-oyl]-L-isoleucine by detailed 2D NMR investigations in conjunction with FAB mass spectrometry and acidic hydrolyses. Complete assignment of the diastereotopic methylene protons of the ring system could be deduced from the NMR data. In agar dilution assays, 1 exhibited antifungal properties against Cladosporium cucumerinum and antibacterial activity against Bacillus subtilis and Escherichia coli.

Notes: The classical rules for Cope rearrangements predict a transition state with chair form to be favored over the boat form. On the other hand, bridged homotropylidenes, which allow only a boat-form transition state by steric reasons, have extremely low barriers. A controversy about the correct pathway and the different possible intermediates and transition states of the reaction has gone on for years. In this work, the hypersurfaces of barbaralane, in comparison with the boat- and chair-form of hexa-1,5-diene, are computed by the ab inito CASSCF (6,6)/6-31G** method starting with UMP2/6-31G** natural orbitals (NO's). All three hypersurfaces show characteristic features, and, moreover differ from each other. A hitherto undiscussed intermediate, bicyclo[2.2.0]hexane, was localized on the boat-hexa-1,5-diene pathway. So it is noteworthy that our transition state for the boat-hexa-1,5-diene does not correspond to the transition states found by other authors for this conformation. The computed enthalpies of activation of boat- and chair-hexa-1,5-diene, and barbaralane are in good agreement with the experimental data.

Notes: As one of the regulatory gene products in the HIV-1 genome, Rev protein must be translocated from the nucleus to the cytoplasm to exert its function. Therefore, inhibition of Rev protein translocation could be a useful target for HIV therapy. An extract from the Streptomyces strain A92-308902 with very potent inhibitory activity was found in the course of a high throughput screening with a Rev translocation assay (RTA). Bioassay-guided fractionation with gel filtration, normal-phase and reversed-phase chromatography yielded six RTA-active metabolites belonging to the leptomycin family, the known leptomycin A (1), leptomycin B (2), kazusamycin B (3), and kazusamycin A (4). and the hitherto unknown dilactonmycin (5) and delactonmycin (6), together with an inactive cyclic hexadepsipeptide L-156,620 (7). The structures were established mainly by spectroscopic methods (UV, FT-IR, FAB-MS, 1H-NMR, 13C-NMR(JMOD), DQ-COSY, ROESY, HSQC, and HMBC). The configuration of all C=C bonds of 1-6 was unambiguously established by analysis of coupling constants and ROESY spectra. All isolated leptomycins 1-6 inhibit Rev translocation at nanomolar concentrations. Six derivatives (2a-c and 4a-c) of leptomycin B (2) and kazusamycin A (4) were also prepared and tested in the RTA for preliminary investigations on structure-activity relationships.

Notes: The olefins mentioned in the title were copolymerized with CO in the presence of palladium catalysts modified with dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine. Productivities up to 95 g/(gPd · h) were achieved. The obtained copolymers were recovered in the pure, regio- und stereoregular polyketone structures3. The isotactic poly[2-benzyl-1-oxopropane-1,3-diyl] (3a) and its analogues 3b, c were found to isomerize to the corresponding spirocyclic poly[3-(arylmethyl)tetrahydrofuran-2,2-5,5-tetrayl-2-oxy-2-methylene]s 4 in a suspension in CHC13, thus indicating that the spiroketal structure is thermodynamically the most stable for these copolymers. However, the atactic material did not undergo any structural transformation. These results show that regularity at the centers of chirality in the main chain is a prerequisite for the conversion of the polyketone to the spiroketal structure.

Notes: Methyl 2-acetyl-3-{[2-(dimethylamino)-1-(methoxycarbonyl)ethenyl]amino}prop-2-enoate (4) and phenyl-methyl 2-acetyl-3-{[2-(dimethylamino)-1(methoxycarbonyl)ethenyl]amino}prop-2-enoate (5) were prepared in three steps from the corresponding acetoacetic esters, and used as reagents for the preparation of N3-protected 3-amino-4H-pyrido[1,2-a]pyrimidin-4-ones 10-12, 5H-thiazolo[3,2-a]pyrimidin-5-one 13, 4H-pyrido[1,2-a]-pyridin-4-one 19 and 2H-1-benzopyran-2-ones 20-23. Free 3-amino-4H-pyrido[1,2-a]pyrimidin-4-ones 24-26 were prepared from 10-12 by removal of the 2-(methoxycarbonyl)-3-oxobut-1-enyl or 3-oxo-2-[(phenyl-methoxy)carbonyl]but-1-envl as N-protecting group by various methods.

Notes: Cyclophanes 3 and 4 were prepared as initiator cores for the construction of dendrophanes (dendritic cydophanes) 1 and 2, respectively, which mimic recognition sites buried in globular proteins. The tetra-oxy[6.1.6.1]paracyclophane 3 was prepared by a short three-step route (Scheme 1) and possesses a cavity binding site shaped by two diphenylmethane units suitable for the inclusion of flat aromatic substrates such as benzene and naphthalene derivatives as was shown by 1H-NMR binding titrations in basic D2O phosphate buffer (Table 1). The larger cyclophane 4, shaped by two wider naphthyl(phenyl)methane spacers, was prepared in a longer, ten-step synthesis (Scheme 2) which included as a key intermediate the tetrabromocyclophane 5. 1H-NMR Binding studies in basic borate buffer in D2O/CD3OD demonstrated that 4 is an efficient steroid receptor. In a series of steroids (Table 1), complexation strength decreased with increasing substrate polarity and increasing number of polar substituents; in addition, electrostatic repulsion between carboxylate residues of host and guest also affected the binding affinity strongly. The conformationally flexible tetrabromocyclophane 5 displayed a pronounced tendency to form solid-state inclusion compounds of defined stoichiometry, which were analyzed by X-ray crystallography (Fig. 2). 1,2-Dichloroethane formed a cavity inclusion complex 5a with 1:1 stoichiometry, while in the 1:3 inclusion compound 5b with benzene, one guest is fully buried in the macrocyclic cavity and two others are positioned in channels between the Cyclophanes in the crystal lattice. In the 1:2 inclusion compound 5c, two toluene molecules penetrate with their aromatic rings the macrocyclic cavity from opposite sides in an antiparallel fashion. On the other hand, p-xylene (= 1,4-dimethylbenzene) in the 1:1 compound 5d is sandwiched between the cyclophane molecules with its two Me groups penetrating the cavities of the two macrocycles. In the 1:2 inclusion compound 5e with tetralin (= 1,2,3,4-tetrahydronaphthalene), both host and guest are statically disordered. The shape of the macrocycle in 5a-e depends strongly on the nature of the guest (Fig. 4). Characteristic for these compounds is the pronounced tendency of 5 to undergo regular stacking and to form channels for guest inclusion; these channels can infinitely extend across the macrocyclic cavities (Fig. 6) or in the crystal lattice between neighboring cyclophane stacks (Fig. 5). Also, the crystal lattice of 5c displays a remarkable zig-zag pattern of short Br…O contacts between neighboring macrocycles (Fig. 7).

Notes: Photolysis and Ag-benzoate-catalyzed decomposition of the diazo ketones 2 and 4 derived from Z-Ala-OH and Z-Ala-Ala-OH in the presence of oligonucleotide derivatives bearing at the 5′-terminus an NH2 instead of the OH group, or an aminohexyl phosphate group lead to Z-protected 3-aminobutanoyl and to Z-Ala-β-HAla derivatives, respectively (conjugates 12, 13, and 17-23, Schemes 3-5), In solution, this amide-forming acylation reaction could be realized only with oligomers containing up to 8 unprotected nucleotide building blocks (Schemes 3 and 4). With the analogous polymer-bound and protected oligonucleotide derivatives as amino nucleophiles, excellent yields were obtained with all chain lengths tested (up to 15mer Scheme 5), The products were purified by reversed-phase HPLC and characterized by MALDI-TOF mass spectrometry (Figs. 2-4, Table 2) and by capillary gel electrophoresis (Fig.2).

Notes: We describe a versatile novel approach for the synthesis of 2, 4, 6-trisubstituted pyrimidines on solid support. Thus, polymer-boun J thiouronium salt 2 reacted in high yield in a cyclocondensation reaction with the acetylenic ketones 3 to form, after tert-butyl-ester cleavage, the polymer-bound carboxylic acids 4, which were cleaved by oxidation with 3-chloroperbenzoic acid and pyrrolidine to form the 2-pyrrolidinylpyrimidine-4-carboxylic acids 6a-c in high yields and purities without further purification (Scheme 1). Alternatively, acid 4a was subjected to an Ugi four-component condensation which gave the polymer-bound Ugi products 9a-e in good yields (Scheme 2). Multidirectional cleavage reaction of sulfone 8a with different nucleophiles resulted in the clean formation of pyrimidine-4-carboxamides 10-13 (Scheme 3). This strategy combines efficiently solid-phase chemistry with a multicomponent reaction and a multidirectional cleavage step to form highly diverse pyrimidines in a parallel array.

Notes: The title compounds 4 are obtained by photolysis of simple N-alkylpyridinium salts in H2O or alcohol. On reaction with [Fe2(CO)9] in THF, 4 gives bicyclic tricarbonyliron complexes 13a-d, which on oxidative decomplexation with ceric ammonium nitrate afford cis-fused cyclopenteno-β-lactams 15a-d.

Notes: The first crystal structure of a molybdenum complex 9 with a hydrogenated pterin and a sulfur ligand contributes to the discussion about the active center of molybdenum and tungsten enzymes containing a molybdopterin cofactor. Complex 9 was synthesized through a redox reaction of [MoVIO2 (LN-S2)] (8; LN-S2 = pyridine-2, 6-bis(methanethiolato)) with 5, 6, 7, 8-tetrahydropterin (7). 2 HCl (H4Ptr.2 HCl). The complex crystallizes, with a non-coordinating Cl-atom acting as a counterion, in the monoclinic space group C2/c (No. 15) with cell dimensions a = 22.900(5), b = 10.716(2), c = 17.551(4) Å, β = 120.36(3)°, and Z = 8. We interpret 9 as [MoIVO(LN-S2)(H+-q-H2Ptr)]Cl (q = quinonoid; H2Ptr = dihydropterin), i.e., a MoIV monooxo center coordinated by a pyridine-2, 6-bis(methanethiolato) ligand and a protonated dihydropterin. The spectroscopic properties of this new complex are comparable to those of other crystalline molybdenum complexes of hydrogenated pterins without additional S-coordination. The slightly H2O-soluble complex 9 reacts with the natural enzyme substrate DMSO very slowly, possibly due to the lack of easily dissociable ligands at the metal center.

Notes: The solid-state structures of three stereoisomer, 1-3, of the cyclic tetramer of 3-aminobutanoic acid are presented. These cyclo-β-peptides were found to be highly insoluble materials, and it proved to be impossible to grow crystals of sufficient quality for X-ray single-crystal analysis. The samples of 1-3 were, however, suitable candidates for structure determination from powder diffraction data (Fig. 1), and the application of this method is described. All three isomers have been found to adopt tubular structures (Figs. 2-4) in a fashion similar to those already observed for certain cyclo-α-peptides. The stacks of 16-membered rings are held together by four nonlinear C=O…H—N H-bonds between pairs of molecules (Fig.5).

Notes: β-Cryptoxanthin (1) was acetylated and then epoxidized with monoperoxyphthalic acid. After hydrolysis, repeated chromatography, and crystallization, (3S,5R,6S)-5,6-epoxy-β-cryptoxanthin (3), (3S,5S,6R)-5,6-epoxy-β-cryptoxanthin (4), (3R,5′R,6′R)-5′,6′-epoxy-β-cryptoxanthin (5), (3S,5R,6S,5′R,6′S)-5,6:5′,6′-diepoxy-β-cryp-toxanthin (6), and (3S,5S,6R,5′S,6′R)-5,6:5′,6′-diepoxy-β-cryptoxanthin (7) were isolated as main products and characterized by their UV/VIS, CD, 1H- and 13C-NMR, and mass spectra. The comparison of the carotenoid isolated from yellow, tomato-shaped paprika (Capsicum annuum var. lycopersiciforme flavum) with 3-5 strongly supports the structure of 3 for the natural product.

Notes: The 14-membered tetraazamacrocyclic Ni2+ and Cu2+ complexes of 4 (1, 4, 8-trimethyl-11-[(2-methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), 5. (1, 4-dimethyl-8, 11-bis[2-(methylthio)ethyl]-l, 4, 8, 11-tetraazacyclotetradecane), and 7 (1, 4, 8, ll-tetrakis[2-(methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), with pne, two, and four methylthio-substituted pendant chains, respectively, and the Ni2+ complex of 6 (1, 4-dimethyl-8, 11-bis (2-methoxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H2O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioether-containing compounds [Ni(5)](ClO4)2, [Cu(5)](ClO4)2, and [Cu(7)](ClO4)2 show a coordination number of 5, whereas that of [Ni(6)](ClO4)2 with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that Ni2+ is reversibly reduced to Ni+ between -0.64 and -0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol is then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in [Ni(6)](ClO4)2 is observed under similar conditions.

Notes: The photochemical synthesis of indole derivatives starting from the indoline-2-thiones 1 is described. Irradiation of indoline-2-thiones 1 in the presence of alkenes 3 gave 2-alkyl-3H-indoles 4-7 or 2-alkylindoles 8-22 through the ring cleavage of the intermediates, spirocyclic amino-thietanes, initially derived by [2 + 2] cycloaddition of the C=S bond of 1 and the C=C bond of 3. Irradiation of 1 in the presence of trialkylamines 26 gave desulfurization products 27-32 and unexpected 3-alkylindoles 33-40. N-Acylindoline-2-thiones 11-p yielded the deacylated products, indoline-2-thiones 1a-b, and ethyl esters 43 through γ-H abstraction by the excited thioamide S-atom when irradiated in CDC13/EtOH or benzene/EtOH. Oxygen analogues 2a-d also underwent intramolecular H abstraction to give the indolin-2-ones 2e-f and ethyl esters 43 in a similar way.

Notes: Antioxidant activity guided fractionation of extracts of the aerial parts of the title plant and HPLC separation yielded a series of oxygenated long-chain alkylcatechols. Their structures were inferred by spectroscopic methods and chemical transformations to be the novel 4-[(2S,4R,6S)-4-(acetyloxy)tetrahydro-6-pentyl-2H-pyran-2-yl]benzene-1,2diol (1a), 4-[(2S,4R6S)-tetrahydro-4-hydroxy-6-pentyl-2H-pyran-2-yl]benzene-1,2-diol (1b), 4-[(3S,5S)-5-(acetyloxy)-3-hydroxydecyl]benzene-1,2-diol (2a), 4-[(3S,5S)3-(acetyloxy)-5-hydroxydecyl]benzene-1,2-diol (2b), (3S,13Z)-1-(3,4-dihydroxyphenyl)-3-hydroxydocos-13-en-5-one (3a), (Z)-1-(3,4-dihydroxyphenyl)docos-13-en-5-one (4), besides the known l-(3,4-dihydroxyphenyl)icosan-5-one (5). The absolute configurations of the optically active compounds which are structurally related to the [n]-gingerols (6) and -diols (7) were established by the high-field 1H-NMR application of Mosher's method. All compounds are in vitro potent antioxidants, inhibiting the Fe2+-catalysed autoxidation of linoleic acid in the same order of magnitude as the commercial antioxidant 2,6-di(tert-butyl)-4-methylphenol (BHT). The dose-dependent inhibitory effects on soybean-lipoxygenase are in the μmol range, that of the most effective compound (3a) in the nmol range, hence being significantly more potent than the Known anti-inflammatory and analgesic drugs indomethacin and nordihydroguaiaretic acid.

Notes: The synthesis and X-ray crystal structure of a europium macrocyctic complex 1, an important catalyst used for the sequence-specific cleavage of RNA, is reported. The role of this metal complex in facilitating phosphate transesterification is discussed.

Notes: Starting from the easily available, highly functionalized acetylenic ketories 4a-i (Scheme 1), novel 2,3,5-trisubstituted thiophenes 1a-i (Scheme 2) were synthesized in good yields using a tandem Michael-addition/intramolecular Knoevenagel-condensation strategy, featuring Cs2CO3/MgSO4 (1:2) as an efficient base to effect the cyclization. Subsequent simple one-step transformations yielded 2,3-disubstituted thiophene-5-carbaidehydes 7a-c, carboxylic-acid derivatives 8, 9, and 11, and alcohol 10 (Scheme 3). These molecules constitute interesting novel thiophene-containing building blocks, useful for the preparation of low-molecular-weight compound libraries by combinatorial and parallel-chemistry techniques.

Notes: Lanthanide picrate complexes with the ligand N,N,N′,N′-tetraphenyl-3,6-dioxaactanediamide (tdd): [Ln(Pic)3(tdd)] (Ln = La, Nd, Eu, Tb, Er) have been prepared in a nonaqueous medium and characterized by elemental analysis, conductivity measurements, IR, and 1H-NMR spectra. The crystal structures of the complexes for Ln = Nd and Er were determined. The early lanthanide, NdIII, crystallizes as the nona-coordinate complex [Nd(Pic)3(tdd)]. 2 CH3CN in the monoclinic space group P21n with a = 11.384(2), b = 18.805(4), c = 27.526(5) Å, β = 99.41(1)°, V = 5832(2) Å3, and Dc = 1.58 gcm-3 for Z = 4. The structure was refined to R = 0.0505, based on 4772 observed Deflections. The late lanthanide, ErIII, forms an octa-coordinate complex [Er(Pic)3(tdd)]; crystals are triclinic, P1, with a = 12.449(2), b = 17.065(2), c = 26.243(4) Å, α = 72.12(1), β = 87.86(1), γ = 84.60(1)°, V = 5282(1) Å3, and Dc = 1.68 g cm-3 for Z, = 4. The structure was refined to R = 0.0469, based on 10666 observed reflections, The results reveal that tdd forms a ring-like structure with its four O-atoms, coordinating to the metal ions as multidentate ligand, together with one O-atom of the bidentate picrate. The structure of the complexes is greatly affected by the ionic radius due to participation of the picrates in coordination.

Notes: Intramolecular [Pd2(dba)3]/tri(2-furyl)phosphine-catalysed (dba = dibenzylideneacetone, PhCH=CHCOCH=CHPh) cyclisations of olefinic propargylic carbonates I provided alk-1-enyl-(3-aza)bicyclo[3.1.0]-hexanes VIII in good yields. A palladium cascade sequence I → II → III → IV → VII → VIII is proposed. Furthermore, chiral propargylic carbonates such as 23, 24 and 25 allowed diastereoselective formation of bicyclo[3.1.0]hexanes 29, 30 and 31, respectively. The first diastereoselective synthesis of the monoterpene, (-)-α-thujone 40 illustrates the potential of the method.

Notes: The structure of rogioldiol A ((-)-1), isolated from the red seaweed Laurencia microcladia, was determined. Employing the exciton-coupling technique for rogioldiol A p-bromobenzoate (2), the absolute configuration at C(9) of (-)-1 was assigned, and, together with extensive NMR experiments, the absolute configuration at C(10) and preferred conformations of (-)-1 were determined. The absolute configuration of the hetero-substituted cyclohexane ring was deduced in analogy from the X-ray structure of 4, a derivative of the aldehyde 3, which was isolated from the same seaweed and is believed to be a degradation product of (-)-1.

Notes: New chromenes annulated with different six-membered azaheterocycles were prepared, i.e., the 3H-pyra-no[3,2-f]quinolines 9/10 and 14, the 8H-pyrano[2,3-h]isoquinoline 11, the 8H-pyrano[3,2-f]quinazolme 12, the 8-H-pyrano[3,2-f]quinoxaline 13, and the 2H-pyrano[2,3-f]isoquinoline 15. The synthesis was achieved using conveniently substituted α,β-unsaturated aldehydes and organotitanium intermediates arising from azaheterocyclic phenols. Their photochromic behaviour (photocolouration yield, UV/VIS spectrum of photomerocyanines, rate constant of thermal bleaching) were studied besides those of corresponding naphthopyrans. The heterocycle effect and the role of substituents in the pyran moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects. Diaryl-substituted azino-fused chromenes, especially isoquinoline derivatives, exhibit increased colourabilities and bathochromically shifted spectra for photomerocyanines which open up new prospects for photochromic applications.

Notes: The 2′,3′-O-isopropylideneuridine (1) reacts with MeI in the presence of an excess of NaH in THF giving 2′,3′-O-isopropylidene-5′-O-methyluridine (2). Prolonged reaction time gives rise to 2′,3′-O-isopropylidene-3,5′-O-dimethyluridine (4). The use of an equimolar amount of base and alkylating agent results predominantly in methylation at N(3) (→ 3).

Notes: We describe a new, efficient synthesis of DX-9065a (4), a potent inhibitor of the blood coagulation enzyme factor Xa (fXa) which has previously been prepared in more than 20 steps. We saved approximately 10 steps starting with a Pd-catalyzed cyanation of the triflate 10 of 7-methoxynaphthalen-2-ol (9). After cleavage of the MeO group with boron tribromide, the triflate 6 was coupled to acrylate 5 in a Heck reaction (→3). The subsequent transformations led to DX-9065 a.

Notes: The Cu2+ and Ni2+ complexes of three reinforced tetraazamacrocycles, containing a piperazine subunit and one or two alkyl substituents at the other two N-atoms have been prepared and their structural properties studied. In solution, the Ni2+ complexes are square-planar and show no tendency to axially coordinate a solvent molecule or an N3- ion. In contrast, the Cu2+ complexes change their geometry depending upon the donor properties of the solvent, being square-planar in MeNO2 and pentacoordinate in DMF. They also easily react in aqueous solution with N3- to give ternary species with pentacoordinate geometry, the stabilities of which have been determined. In the solid state, the X-ray crystal structures of three Cu2+ complexes also show both geometrical arrangements, two having a square-planar, the other one a distorted square pyramidal geometry. The difference behavior of Ni2+ and Cu2+ stems from the fact that the structural change from square-planar to square-pyramidal can easily be accomplished for Cu2+, whereas, for Ni2+, it is accompanied by an electronic rearrangement from the low-spin to the high-spin configuration. The relatively rigid ligands cannot Adapt to the somewhat larger high-spin Ni2+ion.

Notes: N-Monosubstituted 1,3-diamines were selectively functionalized at the secondary N-atom via 2-Ph-substituted hexahydropyrimidine intermediates. Reaction of the diamines with benzaldehyde, followed by treatment with an electrophile and hydrolysis, provided the desired products with excellent selectivity and in high yields. N4,N9-bis[3-phenylprop-2-enoyl]spermine (4a), which was further converted to N1,N1 2-bis[3-phenylprop-2-enoyl]spermine (15) by a transamidation reaction, was prepared by this way in 82% yield from spermine (1). Compound 4a was alternatively synthesized in 83% yield, equally from 1, by a sequence involving intermediary protection of the terminal amino groups.

Notes: As previously shown, oligo- and poly(β-hydroxyalkanoates) have a high tendency to form lamellar crystallites with ca. 50-Å thickness which corresponds to chain lengths of 16 units (Fig. 1). To have monodisperse model compounds, we have now prepared bicyclic derivatives with three parallel (27-29) or two parallel and an antiparallel chain (68-70) consisting of up to 16 3-hydroxybutanoate (3-HB) units. We also prepared dendritic compounds (71-75, 82-85) containing oligo(3-HB) chains which cannot possibly be arranged as in the lamellae; the branching units were prepared from trimesic acid (= benzene-1,3,5-tricarboxylic acid). So far, none of the prepared samples formed crystals or contained crystalline domains which would have been suitable for single-crystal or powder-diffraction X-ray analysis. The terminally deprotected dendrimers (74, 75, and 85) are multi-anionic (up to 12 peripheral CO2H groups) and biodegradable. The macromolecular HB derivatives (molecular weight up to 10150 Da) have been fully characterized by IR, 1H- and 13C-NMR, [α]D, and elemental analysis. Especially important is the analysis by mass spectrometry with the MALDI-TOF technique (Fig. 2), proving that the products are monodisperse; application of a new variation of this MS method (post source decay = PSD or fragment analysis by structural time of flight = FASTTM) allows for the observation of metastable fragment ions and, thus, is a tool for structural oligomer analysis (Fig. 3).

Notes: 5-Methyl-1,4-naphthoquinone (1) is a remarkable probe to study hydrogen and proton transfer reactions. The photoenol 4-hydroxy-5-methylidene naphthalen-1 (5H)-one (2) is formed in the ground state within 2 ps of excitation and with a quantum yield of unity, presumably through a conical intersection of the S0 and S1 hypersurfaces. In aqueous acid, enol 2 is hydrated to 5-(hydroxymethyl)naphthalene-1,4-diol 3 (X = OH, Scheme 1). The rate of hydration of 2 increases linearly with acid concentration from ca. 1.5 × 104 s-1 at pH 6 to reach a maximum value of 9 ×107 s-1 when the remaining carbonyl function is protonated, pKa(2+) = 1.1. Contrary to an earlier suggestion, the rate-determining step in the acid-catalyzed hydration of 2 is addition of water to the conjugate acid 2+. Pronounced acceleration of the decay rate of 2 by hydrazoic-acid buffers indicates competitive trapping of 2+ by the azide ion. In neutral-to-weakly-basic solutions, enol 2 reacts by ionization, pKa(2) = 6.5, and nearly diffusion-controlled condensation of the carbanionic species 2- with quinone 1. Proto-nation at the methylidene C-atom does not compete measurably with protonation on carbonyl O-atom, despite a Substsial thermodynamic basic for carbon Portoation of ca. 50 kJ mol-1 for 2 and 100 mol-1 for 2-.

Notes: O-Alkylation of 8-hydroxy-1H-quinolin-2-one (1) afforded 8-(2-oxopropoxy)-1H-quinolin-2-one (2) which was immediately cyclized to form the tricyclic 2,3-dihydro-3-hydroxy-3-methyl-5H-pyrido[1,2,3-de][1,4]benzoxazine,-5-one (3). The Reformatsky-type condensation of 3 furnished antiplatelet 8-[(2,3,4,5-tetrahydro-2-methyl-4-methylidene-5-oxofuran-2-yl)melhoxy]-1H-quinolin-2-one (4). Its counterparts 7a-f, Ph-substituted at C(2) of the furan ring, were obtained from 1 via alkylation and the Reformatsky-type condensation. Although compound 4 was less active against platelet aggregation than 7a-f, it was the only compound which exhibited significant inhibitory activity on high-K+ medium, Ca2+-induced vasoconstriction and was more active than most of its Ph-substituted counterparts against norepinephrine-induced vasoconstrictions.

Notes: The two structurally similar 20-phenyl- and 20-(4-methoxyphenyl)-11-(nitrosooxy)pregnan-20-ol derivatives 4 and 7 behave differently under photolytic conditions, the former nitrous acid ester affording, as a main product, the benzo-fused hexacyclic compound 9, and the latter the 21-nitro derivative 12. Mechanistic aspects of these transformations are discussed.

Notes: The synthesis of a variety of potent macrocyclic growth hormone secretagogues, i.e. 5, 9, 12, and 20-22, based on the known lead structure L-692,429 (1) is described. These conformationally constrained growth hormone secretagogues were prepared by joining the two essential pharmacophores, the amino-acid side chain at the 1H-1-benzazepine moiety and the 1,1′-biphenyl moiety with a variety of linkers. The most potent analog was found to be L-744,080 (21), a derivative in which a 2′-carboxamide moiety at 1,1-biphenyl is N,O-joined to the OH group of the (2-hydroxypropyl)amino-acid side chain by a C4 ester linker. This potent analog may be useful in determining the bound conformation of the benzolactam class of growth hormone secretagogues at the newly identified GHS receptor, L-744,080 (21) with an ED50 of 20 nM was up to fifty times more potent than the seco-acid precursor and 3-fold more potent than the parent 2′-tetrazole compound L-692, 429 (1).

Notes: Addition of CH2N2 to 2,3:5,6-di-O-isopropylidene-1-thio-mannono-1,4-lactone (1) gave the 2,5-dihydro-1,3,4-thiadiazole 2 and the 4,5-dihydro-1,2,3-thiadiazole 3. First-order kinetics were observed for the thermolysis of 3 (Scheme 3) at 80-110° in C6D5Cl solution and of 2 (Scheme 3) at 20-35° in CDC13, respectively. The 1,2,3-thiadiazole 3 led to mixtures of the thiirane 9, the starting thionolactone 1, the thiono-1,5-lactone 8, and the enol ether 7, while the isomeric 1,3,4-thiadiazole 2 led to mixtures of the anomeric thiiranes 9 and 12, the O-hydrogen S,O,O-ortholactone α-D-14, the S-methyl thioester 15, the S,S,O-ortholactone 13, and the 2,3:5,6-di-Oisopropylidene-mannono-1,4-iactone (16). Pure products of the thermolysis were isolated by semipreparative supercritical fluid chromatography (SFC), whereas preparative HPLC led to partial or complete decomposition. Thus, the β-D-mannofuranosyl β-D-mannofuranoside 10, contaminated by an unknown S species, was isolated by preparative HPLC of the crude product of thermolysis of 3 at 115-120° and partially transformed in CD3OD solution into the symmetric di(α-D-mannofuranosyl) tetrasulfide 11. Its structure was evidenced by X-ray analysis. Similarly, HPLC of the thermolysis product of 2 gave the enethiol 17, the sulfide 19, and the mercapto alcohol 18 as secondary products. Thermolysis of the thiirane 9 at 110-120° (Scheme 4) led to the anomeric thiirane 12 which was transformed into mixtures of the enethiol 17 and the enol ether 7. Addition of H2O to 17 and 7 gave the corresponding hemiacetals 18 and 20. The mechanism of the thermolysis of the dihydrothiadiazoles 2 and 3, and the thiiranes 9 and 12 is discussed.

Notes: α-Substituted N-acylbornane-10, 2-sultams 6, 9, and 10 can be converted into enantiomerically pure ketones 5. 13, and 14, respectively, via a two-step procedure involving a known mercaptolysis reaction followed by an [Fe(acac)3]-mediated coupling of the resulting S-benzyl thioesters with Grignard reagents. Furthermore, enantiomerically pure aldehydes 23 can be obtained from α-substituted N-acylbornane-10,2-sultams 6 via a one-step reduction with (i-Bu)2AIH. No epimerization at the α-chiral center is observed during the cleavage reaction whereby the chiral auxiliary, bornane-10,2-sultam 1 or ent-l, was recovered. By using this methodology, several natural products or precursors thereof can be prepared.

Notes: Benzo[a]heptalene has been synthesized by two different approaches. The first one follows a pathway to hexahydrobenzo[a]heptalenone 19a that has been already described by Wenkert and Kim(Scheme). Indeed, 19a was obtained in a mixture with its double-bond-shifted isomer 19b. Reduction of this mixture to the corresponding secondary alcohols 26a/26b and elimination of H2O lead to a mixture of the tetrahydrobenzo[a]heptalenes 23a-d (Scheme7 and 8). Reaction of 23a-d with 2 equiv. of triphenylmethylium tetrafluoroborate in boiling CHCl3, followed by treatment with Me3N in CH2Cl2, generated directly 2, unfortunately in a mixture with Ph3CH that could not be separated from 2 (Scheme 10 and 11). The second approach via dimethyl benzo[a]heptalene-6,7-dicarboxylate (30) (Scheme 12) that was gradually transformed into the corresponding carbaldehydes 37 and 43 (Scheme 14) both of which, on treatment with the Wilkinson catalyst [RhCl(PPh3)3] at 130° in toluene, smoothly decarbonylated, finally gave pure 2 as an unstable orange, viscous oil. UV/VIS, NMR, and mass spectra of 2 are discussed in detail (cf. Chapt.3).

Notes: The stereochemistry of 1,3-dipolar cycloaddition of azomethine ylides derived from aromatic aldehydes and i-proline alkyl esters with several nitroolefins was investigated. Cyclic and acyclic nitroolefins add to the anti form of the ylide in a highly diastereoselective but poorly regioselective manner to give pyrrolizidine derivatives. In a few cases, the stereochemical results strongly support a stepwise mechanism.

Notes: Some 2′-deoxy-1′,2′-seco-D-ribosyl (5′→3′)oligonucleotides (= 1′,2′-seco-DNA), differing from natural DNA only by a bond scission between the centers C(1′) and C(2′), were synthesized and studied in order to compare their structure properties and pairing behavior with those of corresponding natural DNA and homo-DNA oligonucleotides (2′,3′-dideoxy-β-D-glucopyranosyl oligonucleotides). Starting from (-)-D-tartaric acid, 2′-deoxy-1′,2′-secoadenosine derivative 9a and 1′,2′-secothymidine (9b) were obtained in pure crystalline form. Using the phosphoramidite variant of the phosphite-triester method, a dinucleotide monophosphate 1′,2′-seco-d(T2) was synthesized in solution, while oligonucleotides 1′,2′-seco-d[(AT)6], 1′,2′-seco-d(A10) and 1′,2′-seco-d(T10) were prepared on solid phase with either automated or manual techniques. Results of UV- and CD-spectroscopic as well as gel-electrophoretic studies indicated that neither adenine-thymine base pairing (as observed in natural DNA and homo-DNA), nor the adenine-adenine base pairing (as observed in homo-DNA) was effective in 1′,2′-seco-DNA, Furthermore, hybrid pairing was observed neither between 1′.2′-seco-DNA and natural DNA nor between 1′,2′-seco-DNA and homo-DNA.

Notes: Flavo-thiazolio-cyclophane 6 was prepared on a gram scale by an 18-step synthesis (Schemes 3 and 4). This pathway involved the very efficient preparation of bromo-cyclophane 32 (37% yield over 13-steps), which can be readily modified to create various multiply functionalized receptors. This bromide 32 was subsequently converted into the corresponding boronic acid and connected to the 7-bromoflavin 10 (Scheme 2) via Suzuki coupling to give flavo-cyclophane 36. The thiazolium unit was then introduced after quaternization of the tertiary amino groups of 36. Flavo-thiazolio-cyclophane 6, with both prosthetic groups attached in proximity to the well-defined cyclophane binding site, is a functional model for the enzyme pyruvate oxidase. In basic methanolic solution, 6 catalyzes the oxidation of aromatic aldehydes to their corresponding methyl esters. Cyclophane 6 shows saturation kinetics, and the turnover number calculated for the oxidation of naphthalene-2-carbaldehyde to methyl naphthalene-2-carboxylate (kcat = 0.22 s-1) is one of the highest reported for an artificial enzyme. Control experiments showed that the catalytic advantages of 6 result from the macrocyclic binding and reaction site as well as from the covalent attachment of both cofactors to this site. The catalytic cycle is completed by electrochemical re-oxidation of the reduced flavin moiety at a low working electrode potential (- 0.3 V vs. Ag/AgCl), and up to ca. 100 catalytic cycles can be performed on a preparative scale, The intramolecular nature of the electron transfer from the active aldehyde intermediate to the flavin is particularly conducive to the oxidation of unreactive aldehydes.

Notes: The phosphoramidites 6b and 9 as well as the phosphonate 6a derived from 7-(hex-1-ynyl)- and 7-[5-(trifluoroacetamido)pent-1-ynyl]-substituted 7-deaza-2′-deoxyguanosines 1 and 10, respectively, were prepared (Scheme 1). They were employed in solid-phase oligodeoxynucleotide synthesis of the alternating octamers d(hxy7c7G-C)4 (12), d(C-hxy7c7G)4 (13), and d(npey 7c7G-C)4 (15) as well as of other oligonucleotides (see 22-25; Table 2; hxy = hex-1-ynyl, npey = 5-aminopent-1-ynyl). The Tm values and the thermodynamic data of duplex formation were determined and correlated with the major-groove modification of the DNA fragments. A hexynyl side chain introduced into the 7-position of a 7-deazaguanine residue (see 1) was found to fit into the major groove without any protrusion. The incorporation of the (5-aminopent-1-ynyl)-modified 7-deaza-2′-deoxyguanosine 2 into single-stranded oligomers of the type 24 and 25 did not lead to change in duplex stability compared to the parent oligonucleotides. The self-complementary oligomer 15 with alternating npey7c7Gd (2) and dC units did not lead to a cooperative melting, either due to orientational disorder or interaction of the 5-aminopent-1-ynyl moiety with a base or with phosphate residues nearby or on the opposite strand.

Notes: The determination of the chemical structure of a previously unknown Maillard reaction product with an amino acid incorporated in a four-ring structure is reported. The red compounds 1a and 1b, isolated from a thermally treated aqueous solution of furan-2-carbaldehyde and L-alanine, were identified as (S)-4{(E)-1-formyl -2-(2-furyl)ethenyl}-5-(2-furyl)-2-{(E)-(2-furyl)methylidene}-2, 3-dihydro-α-methyl-3-oxo-1H-pyrrole-1-acetic acid and its 2-{(Z)-(2-furyl)methylidene}isomer, respectively, by several 1D- and 2D-NMR techniques, MS, UV, and IR spectroscopy as well as by synthetic experiments. 2D-NOESY and 2D-ROESY experiments performed for conformation analysis indicated the existence of two atropisomers.

Notes: Irradiation (λ = 350 nm) of 1H-[2]benzothiopyran-1-one (2) in the solid state affords selectively and in good yield 6aα, 6bα, 12bα, 12cα -tetrahydrocyclobuta[1, 2-c:4, 3-c′]bis([2]benzothiopyran)-5, 8-dione (3), the head-to-head (HH) cis-cisoid-cis-cyclodimer of 2, X-Ray analysis of 2 confirms that this reaction proceeds according to the well-established topochemical principles. The same dimer 3 is obtained in low yields on irradiation of 10-1 M solutions of 2 in either MeOH or MeCN, while no conversion at all is observed in benzene. On irradiation of 2 in MeCN in the presence of tetrachloroethene, the [2 + 2] photocycloadduct 4 is formed in good yield, the conversion 2 → 4 being efficiently quenched by naphthalene. In contrast, no reaction is observed -on irradiation of 2 in the presence of 2, 3-dimethylbut-2-ene, neither in polar nor in apolar solvents.

Notes: The difference in steric strain between the oxidized and the reduced forms of tetraaminecopper complexes is correlated with the corresponding reduction potentials. The experimentally determined data considered range from -0.54 to -0.04 V (vs. NHE) in aqueous solution and from -0.35 to -0.08 V (vs. NHE) in MeCN. The observed and/or computed geometries of the tetraaminecopper(II) complexes are distorted octahedral or square-pyramidal (4 + 2 or 4+1) with (distorted) square-planar CuN4 chromophores (CuII—N = 1.99-2.06 Å; Cu—O4+2Ax ≈ 2.5 Å; Cu—O4+1ax ≈ 2.3 Å), those of the tetraaminecopper(I) complexes are (distorted) tetrahedral (four-coordinate; CuI—N = 2.12-2.26 Å; tetrahedral twist angle ∅ = 30-90°). The reduction potentials of CuII/I couples with primary-amine ligands and those with macrocyclic secondary-amine ligands were correlated separately with the corresponding strain energies, leading to slopes of 70 and 61 kJ mol-1 V-1, with correlation coefficients of 0.89 and 0.91, respectively. The approximations of the model (entropy, solvation, electronic factors) and the limits of applicability are discussed in detail and in relation to other approaches to compute reduction potentials of transition-metal compounds.

Notes: The reaction of thiobenzophenone (= diphenylmethanethione; 8a) or 9H-fluorene-9-thione (8b) and methyl fumarate (9) in excess PhN3 at 80° yields a mixture of diastereoisomeric thiiranes 10 and 11 (Scheme 1). A mechanism involving the initial formation of 1-phenyl-4, 5-dihydro-1H-1, 2, 3-triazole-4, 5-dicarboxylate 12 by 1, 3-dipolar cycloaddition of PhN3 and 9 is proposed in Scheme 2. The diazo compound 13, which is in equilibrium with 12, undergoes a further 1, 3-dipolar cycloaddition with thioketones 8 to give 2, 5-dihydro-1, 3, 4-thiadiazoles 14. Elimination of N2 yields the thiocarbonyl ylide 15 which cyclizes to the corresponding thiirane. Desulfurization of the thiiranes 10 and 11 with hexamethylphosphorous triamide leads to the olefinic compounds 16 (Scheme 3). The crystal structures of 10a, 11a, and 16b were determined.

Notes: β-Hexapeptides 1-5 and a β-dodecapeptide 6 with sequences containing two different types of β-amino acids (aliphatic proteinageous side chains in the 2- or in the 3-position) have been prepared. CD (Fig. 1) and NMR measurements indicate that, with one exception, the secondary structures formed by these new β-peptides differ from those of isomers studied previously. Detailed NMR analysis of the β-hexapeptide 5 (with alternating β2,β3-building blocks) and molecular-dynamics simulations have produced a minimum energy conformation (Fig. 2,b)which might be described as a novel irregular helix containing ten- and twelve-membered H-bonded rings. This demonstrates the great structural variability of β-peptides, since three different helical secondary structures have been discovered to date.

Notes: Catalytic control of regio-, diastereo-, and enantioselectivity in the 1,3-dipolar cycloaddition of 3-acryl-oyloxazolidin-2-one (4) with different nitrones 2 by the application of a [TiX2(TADDOLato)] complex as the catalyst was developed (TADDOL = α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanol). In the absence of a catalyst, the 1,3-dipolar cycloaddition of 4 with 2 proceeded to give a mixture of regioisomers, whereas, in the presence of a catalyst, the regioselectivity of the reaction could be controlled. Three asymmetric [TiX2(TADDOLato)] catalysts were tested, and it was found that use of the [Ti(OTs)2(TADDOLato)] complex gave complete regioselectivity, high ‘endo’-selectivities (〉 90% d.e.), and enantioselectivities corresponding to 48-70% e.e.