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  • 1985-1989  (918)
  • 1890-1899
  • 1860-1869  (1,706)
  • 1850-1859  (420)
  • 1989  (918)
  • 1866  (412)
  • 1865  (432)
  • 1864  (444)
  • 1863  (418)
  • 1851  (420)
  • Organic Chemistry  (2,928)
  • Immunohistochemistry  (116)
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  • 1985-1989  (918)
  • 1890-1899
  • 1860-1869  (1,706)
  • 1850-1859  (420)
Year
Keywords
  • 101
    Electronic Resource
    Electronic Resource
    Immunohistochemical demonstration and radioimmunoassay of melatonin in the mink pineal gland (1989)
    Springer
    Cell & tissue research 257 (1989), S. 23-28 
    Details
    ISSN: 1432-0878
    Keywords: Melatonin ; Immunohistochemistry ; Radioimmunoassay ; Pineal gland ; Mink, Mustela vison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An antiserum raised against N-amino-3-propyl melatonin bound to a protein carrier was used to visualize melatonin by immunohistochemistry and to measure melatonin concentration by radioimmunoassay in the pineal gland of intact mink females killed throughout the 24 h cycle and females killed after a bilateral ablation of the cervical superior ganglion. Melatonin immunoreactivity revealed by immunofluorescence or by the peroxidase-antiperoxidase complex was observed in the cytoplasm of presumed pinealocytes of all the females. Circadian changes in pineal melatonin content were not visualized by immunohistochemistry; furthermore, immunoreactivity was also present in the pineal gland of the ganglionectomized females. However, the melatonin content measured by radioimmunoassay was significantly higher in the pineal gland from intact females killed during the night compared with that of intact females killed during the day or of ganglionectomized females. The discrepancy between the results obtained using the two methods may arise because immunohistochemistry can detect very small amounts of melatonin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221630
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  • 102
    Electronic Resource
    Electronic Resource
    Calbindin immunoreactivity in the neurons of the spinal cord and dorsal root ganglion of the domestic fowl (1989)
    Springer
    Cell & tissue research 257 (1989), S. 149-153 
    Details
    ISSN: 1432-0878
    Keywords: Calbindin ; Brachial spinal cord ; Dorsal root ganglion ; Immunohistochemistry ; Domestic fowl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of the vitamin D-dependent calcium-binding protein, calbindin, was mapped in the brachial spinal cord and in the 15th dorsal root ganglion of the domestic fowl, using fluorescence immunohistochemistry. Cell somata of the dorsal root ganglion ranged in area from 200 μm2 to 2000 μm2. Sixteen percent of cell bodies displayed calbindin immunoreactivity. Reactivity occurred in both the small and large sensory neurons. These were randomly distributed within each ganglion. In the spinal cord, calbindin immunoreactivity was intense in Lissauer's tract, and in nerve fibres and nerve cell bodies within laminae 1 to 3 of the dorsal horn. Scattered varicose fibres were observed in laminae 4 to 7. Immunoreactivity was intense in laminae 10 where nerve fibres formed a meshwork around the central canal. Immunoreactive perikarya were occasionally observed in the outer region of lamina 10 and between laminae 8 and 9. The perikarya of the large motoneurons of lamina 9 were not reactive although they were enmeshed in calbindin-immunoreactive fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221645
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  • 103
    Electronic Resource
    Electronic Resource
    Projections of neurons with neuromedin U-like immunoreactivity in the small intestine of the guinea-pig (1989)
    Springer
    Cell & tissue research 257 (1989), S. 415-422 
    Details
    ISSN: 1432-0878
    Keywords: Neuromedin U ; Enteric nervous system ; Intestine, small ; Immunohistochemistry ; Neuropeptides ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neuromedin U immunoreactivity was located histochemically in the guinea-pig small intestine. Projections of immunoreactive neurons were determined by analysing patterns of degeneration following nerve lesions. The co-localization of neuromedin U immunoreactivity with immunoreactivity for substance P, neuropeptide Y, vasoactive intestinal peptide and calbindin was also investigated. Neuromedin U immunoreactivity was found in nerve cells in the myenteric and submucous plexuses and in nerve fibres in these ganglionated plexuses, around submucous arterioles and in the mucosa. Reactive fibres did not supply the muscle layers. Most reactive nerve cells in the myenteric ganglia had Dogiel type-II morphology and in many there was co-localization of calbindin, although some Dogiel type-II neuromedin U neurons were calbindin negative. Lesion studies suggest that these myenteric neurons project circumferentially to local myenteric ganglia. Projections from myenteric neurons also run anally in the myenteric plexus, while other projections extend to submucous ganglia, and still further projections run from the intestine to provide terminals in the coeliac ganglia. In the submucous ganglia neuromedin U was co-localized in three populations of nerve cells: (i) those with vasoactive intestinal peptide immunoreactivity, (ii) neurons containing neuropeptide Y, and (iii) neurons containing substance P. Each of these populations sends nerve fibres to the mucosa. Neuromedin U immunoreactivity is thus located in a variety of neurons serving different functions in the intestine and therefore probably does not have a single role in intestinal physiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261844
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  • 104
    Electronic Resource
    Electronic Resource
    Splenic outer periarterial lymphoid sheath (PALS): An immunoproliferative microenvironment constituted by antigen-laden marginal metallophils and ED2-positive macrophages in the rat (1989)
    Springer
    Cell & tissue research 257 (1989), S. 459-470 
    Details
    ISSN: 1432-0878
    Keywords: Spleen ; Periarterial lymphoid sheath (PALS) ; Macrophage subpopulations ; Microenvironment ; B-lymphocytes ; Immune response ; Cell proliferation ; Immunohistochemistry ; Rat (DA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In an attempt to reveal the role of antigen-laden marginal metallophil (MM) and other macrophages in the intrasplenic immune response of a specific B-cell lineage to a thymus-independent type-2 antigen (Ficoll conjugated with fluorescein isothiocyanate), simultaneous immuno-histological observations of the involved cells were performed in the rat. By newly established methods of double or triple immunostainings, time-kinetics of the following parameters were studied and compared: (1) the antigen, (2) the specific antibody-forming cells (AFC) directed to the fluorescein-isothiocyanate determinant, (3) proliferating cells labeled with 5-bromo-2′-deoxyuridine (BrdU), and (4) macrophage subpopulations recognized by monoclonal antibodies (ED2 and ED3). The antigen localized stably not only in the marginal-zone macrophages but also in the MM except around the follicular area. The increase of BrdU-positive cells was observed from day 2 up to day 4 after antigen injection mostly in the periphery of the periarterial lymphoid sheath (outer PALS), which indicated antigen-induced proliferation. As a novel finding, the majority of AFC, both BrdU-positive and -negative, were either closely associated with the antigen-laden MM, or forming cell clusters with ED2-positive macrophages in the outer PALS. In contrast, there were very few AFC in juxtaposition to antigen-free MM in the follicular area or the antigen-laden marginal zone macrophages. The results led to the proposal of a hypothesis that the antigen-laden MM together with ED2-positive macrophages constitute an immunoproliferative microenvironment for the plasmacellular reaction by accumulating the antigen-specific B-cell lineage and promoting these cells to differentiate into the AFC and to proliferate in the outer PALS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221456
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  • 105
    Electronic Resource
    Electronic Resource
    Immunocytochemical localization of hypocalcin in the endocrine cells of the corpuscles of Stannius in three teleost species (trout, flounder and goldfish) (1989)
    Springer
    Cell & tissue research 255 (1989), S. 651-656 
    Details
    ISSN: 1432-0878
    Keywords: Corpuscles of Stannius ; Hypocalcin ; Immunohistochemistry ; Carassius auratus ; Hippoglossoides elassodon ; Salmo gairdneri
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In order to identify the cell-type responsible for the production of hypocalcin (the recently isolated hypocalcemic hormone of teleost fish), the corpuscles of Stannius (CS) of trout, flounder and goldfish, were immunocytochemically stained with antisera raised against trout hypocalcin. The secretory granules of the type-1 cells of the CS, considered to be the hypocalcin-producing cells, showed intense immunoreactivity in all species examined. However, in trout and flounder, the secretory granules produced by the type-2 cells, which have been suggested to represent a functionally different cell-type, also showed an intense immunoreactivity. In goldfish, no type-2 cells were observed. We tentatively conclude that type-1 and type-2 cells represent structurally different forms of the same functional cell-type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218804
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  • 106
    Electronic Resource
    Electronic Resource
    Vasoactive intestinal polypeptide-like immunoreactivity in the bovine heart: high degree of coexistence with neuropeptide Y-like immunoreactivity (1989)
    Springer
    Cell & tissue research 256 (1989), S. 125-135 
    Details
    ISSN: 1432-0878
    Keywords: Heart-conducting system ; Vasoactive intestinal polypeptide (VIP) ; Neuropeptide Y ; Dopamine-betahydroxylase ; Immunohistochemistry ; Cow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary It is not known whether VIP coexists with other neuropeptides or neurotransmitters in the heart. In the present study, the distribution of nerve fibers showing VIP-like immunoreactivity (VIP-LI) in various parts of the bovine heart was compared with that of fibers possessing neuropeptide Y (NPY)- and dopamine-beta-hydroxylase (DBH)-LI. It was found that fibers showing VIP-LI most regularly occurred in the regions of sinuatrial and atrioventricular nodes and intracardiac ganglia, the nerve fibers being associated with nodal and ganglionic cells and arterial walls. Furthermore, it was observed that almost all fibers showing VIP-LI also exhibited NPY-LI. The fibers displaying VIP-LI occurred close to fibers endowed with DBH-LI, and on some occasions it appeared that varicosities showing immunolabeling for VIP also displayed DBH-LI. VIP- and NPY-LI, but not DBH-LI, was detected in some of the intracardiac ganglionic cells. The observations are discussed in relation to the previously known distribution and function of VIP in the heart and other organs. Further studies examining the effects of VIP and NPY in the heart should take into account possible interactions between these two peptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224726
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  • 107
    Electronic Resource
    Electronic Resource
    The relationship between gastrin cells and bombesin-like immunoreactive nerve fibres in the gastric antral mucosa of guinea-pig, rat, dog and man (1989)
    Springer
    Cell & tissue research 257 (1989), S. 171-178 
    Details
    ISSN: 1432-0878
    Keywords: Gastrin ; Gastrin-releasing peptide ; Bombesin ; Stomach ; Autonomic innervation ; Immunohistochemistry ; Guinea pig ; Rat ; Dog ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The relationship between bombesin-like immunoreactive (bombesin-LI) nerve fibres and gastrin-LI G-cells was examined in gastric antral mucosa from guineapig, rat, dog and man using a double-labelling fluorescence immunohistochemical technique. The greatest density of bombesin-LI nerve fibres was found within the basal mucosa in all species and the density of innervation decreased towards the luminal surface. Most G-cells were in a band occupying approximately the middle third of the mucosa. The proportion of G-cells found within a distance of 2 μm from bombesin-LI nerve fibres was low in all species (6% in the guinea-pig, 22% in the rat, 14% in the dog, and 9% in the human). It is proposed that the neuropeptide released from bombesin-LI antral mucosal nerve fibres traverses distances of greater than several μm to reach the target G-cells. This may be achieved by passage through the mucosal microcirculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221648
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  • 108
    Electronic Resource
    Electronic Resource
    Immimohistochemical localization of corticotropin-releasing factor in selected brain areas of the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia) (1989)
    Springer
    Cell & tissue research 257 (1989), S. 155-161 
    Details
    ISSN: 1432-0878
    Keywords: Corticotropin-releasing factor (CRF) ; Immunohistochemistry ; Neurosecretory system ; Hypothalamus ; Nucleus striae terminalis ; European starling (Sturnus vulgaris) ; Song sparrow (Melospiza melodia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Corticotropin-releasing factor (CRF) was localized in the brains of two passerine species, the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), by means of immunohistochemistry. The hypothalamic distribution of this peptide in these species includes a complex of immunoreactive perikarya observed in the paraventricular nucleus (PVN), in both its medial and lateral divisions. Nerve fibers were also seen running from these areas to the anterior median eminence (AME) where a terminal field is apparent. A wide variety of extra-hypothalamic nuclei containing CRF-immunoreactive cells and fibers were identified. An apparent CRF terminal field can be visualized in the lateral septum. A dense fiber plexus is present in the nucleus accumbens (Ac) and more caudally in the nucleus of the stria terminalis (nST). In colchicinepretreated animals, it was revealed that these areas also contain CRF-stained perikarya. The pattern of CRF immunoreactivity in the Ac-nST complex is continuous, with no distinction apparent between the nuclei. The medial preoptic area (mPOA) and the adjacent diagonal band of Broca contain CRF-fibers, while cells are apparent in the mPOA. In the mesencephalon, cells were visualized in the midbrain central gray; a terminal field and scattered positively stained perikarya were found in areas more ventral to the central grey that are adjacent to the third cranial nerve. Scattered cells were also seen at the border of the nucleus intercollicularis-nucleus mesencephalicus lateralis, pars dorsalis complex. In contrast to mammalian studies, no immunoreactive nerve fibers or perikarya were observed in telencephalic areas homologous to the mammalian neocortex. These studies confirm the presence of a CRF path-way regulating pituitary function and suggest a broad role played by CRF as a neuromodulator or neurotransmitter in autonomic and possibly behavioral activities in these species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221646
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  • 109
    Electronic Resource
    Electronic Resource
    Immunohistochemistry of vacuoles occurring in rat hepatocytes after retinol administration (1989)
    Springer
    Cell & tissue research 257 (1989), S. 263-268 
    Details
    ISSN: 1432-0878
    Keywords: Retinol ; Vacuoles ; Immunohistochemistry ; Plasma proteins ; Hepatocytes ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The vacuoles occurring in rat hepatocytes after intraportal injection of retinol (33 or 67 μg) were examined immunohistochemically using respective antibodies against rat albumin, human retinol-binding protein, human ceruloplasmin, human α 1-antitrypsin, human transferrin, and human prealbumin as representative plasma proteins. The occurrence of the vacuoles reached a numerical maximum 30 min after injection of 67 μg retinol, followed by a temporal decrease. Hepatocytes from control rats, which had been intraportally injected with either blood plasma diluted to 2/3 concentration or with retinol palmitate solvent (castor oil) dissolved in blood plasma, showed immunoreactive fine granules without the occurrence of vacuoles in the cytoplasm. Identical vacuoles in serial sections appeared immunohistochemically either immunoreactive or non-immunoreactive for all the antibodies used, with rare exceptions. The occurrence of several rare exceptions suggested that 2 kinds of vacuoles might be formed in different cytoplasmic compartments. A zonal distribution of vacuoles was apparent in the hepatic laminae (or acini) within the liver lobules. The vacuoles were predominantly distributed in zone 2, and to a lesser extent in zone 3 and zone 1 in that order.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261829
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  • 110
    Electronic Resource
    Electronic Resource
    Localization and characterization of neuropeptide Y-like peptides in the brain and islet organ of the anglerfish (Lophius americanus) (1989)
    Springer
    Cell & tissue research 257 (1989), S. 303-311 
    Details
    ISSN: 1432-0878
    Keywords: Neuropeptide Y ; Anglerfish peptide YG ; Brain ; Pancreas, endocrine, innervation ; Immunohistochemistry ; Radioimmunoassay ; High performance liquid chromatography ; Anglerfish, Lophius americanus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Results from a previous report demonstrate that more than one molecular form of neuropeptide Y-like peptide may be present in the islet organ of the anglerfish (Lophius americanus). Most of the neuropeptide Y-like immunoreactive material was anglerfish peptide YG, which is expressed in a subset of islet cells, whereas an additional neuropeptide Y-like peptide(s) was localized in islet nerves. To learn more about the neuropeptide Y-like peptides in islet nerves, we have employed immunohistochemical and biochemical methods to compare peptides found in anglerfish islets and brain. Using antisera that selectively react with either mammalian forms of neuropeptide Y or with anglerfish peptide YG, subsets of neurons were found in the brain that labelled with only one or the other of the antisera. In separate sections, other neurons that were labelled with either antiserum exhibited similar morphologies. Peptides from brains and islets were subjected to gel filtration and reverse-phase high performance liquid chromatography. Radioimmunoassays employing either the neuropeptide Y or peptide YG antisera were used to examine chromatographic eluates. Immunoreactive peptides having retention times of human neuropeptide Y and porcine neuropeptide Y were identified in extracts of both brain and islets. This indicates that peptides structurally similar to both of these peptides from the neuropeptide Y-pancreatic polypeptide family are expressed in neurons of anglerfish brain and nerve fibers of anglerfish islets. The predominant form of neuropeptide Y-like peptide in islets was anglerfish peptide YG. Neuropeptide Y-immunoreactive peptides from islet extracts that had chromatographic retention times identical to human neuropeptide Y and porcine neuropeptide Y were present in much smaller quantities. These results are consistent with the hypothesis that peptides having significant sequence homology with human neuropeptide Y and porcine neuropeptide Y are present in the nerve fibers that permeate the islet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261834
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  • 111
    Electronic Resource
    Electronic Resource
    Reactivity of monoclonal islet cell antibodies on normal hyperplastic and neoplastic thyroid C-cells (1989)
    Springer
    Cell & tissue research 257 (1989), S. 437-443 
    Details
    ISSN: 1432-0878
    Keywords: Monoclonal islet antibodies ; Thyroid C-cells ; Differentiation antigens ; Immunohistochemistry ; Cow, Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Thyroid C-cell reactivity to 15 monoclonal antibodies raised against a series of pancreatic islet cells (H[human]ISL, B[bovine]ISL and R[rat]ISL) was evaluated using an indirect immunoperoxidase technique on frozen thyroid sections. Of the monoclonal anti-islet cell antibodies, five reacted specifically with bovine C-cells or human hyperplastic and neoplastic C-cells but not with follicular cells. Two monoclonal antibodies of the bovine series showed strong immunoreactivity with C-cells and only a weakly positive immunostaining of follicular cells. Five monoclonal antibodies reacted with both thyroid C-cells and follicular cells, whereas 3 monoclonal anti-islet cell antibodies did not stain any cell type of the thyroid. In human medullary carcinomas, calcitonin- and somatostatin-producing neoplastic cells were immunoreactive with the same monoclonal antibodies as were normal human C-cells. The protein bands identified by the monoclonal antibodies in human medullary carcinomas had the same molecular weight as those from pancreatic islet extracts. Our study demonstrates the presence of similar differentiation antigens on thyroid C-cells and pancreatic islet cells; this further illustrates common modes of differentiation and specialisation of these embryologically different members of the dispersed neuroendocrine system. The crossreactivity of seven of the monoclonal antibodies investigated with follicular epithelium of the thyroid suggests the existence of common antigenic determinants in different endocrine organs and may partly explain the multiple organ autoimmune response found in patients with polyendocrine diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261846
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  • 112
    Electronic Resource
    Electronic Resource
    Immunogold localisation of endogenous immunoglobulin-G in ultrathin frozen sections of the human placenta (1989)
    Springer
    Cell & tissue research 257 (1989), S. 603-607 
    Details
    ISSN: 1432-0878
    Keywords: Placenta ; Immunoglobulin G ; Endocytosis ; Immunohistochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Endogenous immunoglobulin-G was localised in ultrathin frozen sections of human term placenta by use of an indirect immuno electron-histochemical methodology. Immunoreactivity of endogenous IgG to rabbit anti-human immunoglobulin-G antibody was visualised by use of protein-A — colloidal gold complex. Gold marked the syncytiotrophoblast in both coated and uncoated regions of the apical plasmalemma, in vesicles and multivesicular bodies, and in vesicles near the basal plasmalemma. Immunoreactivity was also seen in the interstitial space between the trophoblast and the fetal endothelial layer as well as in various types of vesicles within the endothelial cells. No immunoreactivity was seen in the intercellular clefts of the endothelium. The pattern of localisation observed is consistent with receptor-mediated uptake of immunoglobulin-G into the syncytiotrophoblast of the human placenta followed by release into the interstitial space and then vesciular transport through the endothelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221471
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  • 113
    Electronic Resource
    Electronic Resource
    The occurrence and distribution of peptide- or 5-HT-containing nerves in the swimbladder of four different species of teleosts (Gadus morhua, Ctenolabrus rupestris, Anguilla anguilla, Salmo gairdneri) (1989)
    Springer
    Cell & tissue research 257 (1989), S. 641-647 
    Details
    ISSN: 1432-0878
    Keywords: Neuropeptides ; Immunohistochemistry ; Swimbladder ; Gas gland ; Gadus morhua ; Ctenolabrus rupestris ; Anguilla anguilla ; Salmo gairdneri (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The innervation of the swimbladder in four different teleost species has been studied by the use of immunohistochemical methods. The teleosts examined belong to two different groups regarding their swimbladder morphology: physoclists (the cod, Gadus morhua and the goldsinny wrasse, Ctenolabrus rupestris) and physostomes (the eel, Anguilla anguilla and the rainbow trout, Salmo gairdneri). Vasoactive intestinal polypeptide-like immunoreactivity was demonstrated in nerves of the swimbladder walls of all four species, and in the gas glands of the cod and the goldsinny wrasse. Substance P-like immunoreactivity was shown in swimbladders of the cod, eel and rainbow trout but not the goldsinny wrasse. Immunoreactivity to met-enkephalin antiserum was revealed in the swimbladder walls of the eel and the goldsinny wrasse, while neurotensin-like immunoreactivity was present in the goldsinny wrasse and rainbow trout swimbladders. Neurotensin-like immunoreactivity was also seen in the gas gland of the goldsinny wrasse. 5-Hydroxytryptamine immunoreactivity was found in endocrine cells in the pneumatic duct of the eel and in the swimbladder walls of the goldsinny wrasse and the rainbow trout. In conclusion, all teleosts examined showed a very close resemblance in the peptidergic/tryptaminergic innervation of the swimbladder to that of the gut, inasmuch as the immunoreactivity present in the swimbladders always occurred in the gut of the same species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221475
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  • 114
    Electronic Resource
    Electronic Resource
    Imunohistochemical demonstration of langerhans' cell in cholesteatoma using an antiserum against S-100 protein (1989)
    Springer
    European archives of oto-rhino-laryngology and head & neck 246 (1989), S. 48-52 
    Details
    ISSN: 1434-4726
    Keywords: Cholesteatoma ; Langerhans' cell ; S-100 protein ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The epidermal Langerhans' cells play an important role in immunological reactions resulting from chronic inflammations of the skin. Recently, S-100 protein, one of the nervous-system-specific proteins, has been shown to be a useful marker for the epidermal Langerhans' cells. We investigated the localization of Langerhans' cells in human cholesteatoma specimens by means of an immunohistochemical method for detecting S-100 protein. A large number of Langerhans' cells containing S-100 protein immunoreactivity were found in the epithelium of the cholesteatoma and also in the subepithelial region. This immunoreactivity was detected both in the cytoplasm of the Langerhans' cells and their dendritic processes along their entire lengths. The number of S-100 positive Langerhans' cells in cholesteatoma associated with otorrhea increased significantly as compared with normal epithelium from the external auditory canal and tympanic membrane, while no increase in the number of S-100-positive cells was recognized in cholesteatoma without otorrhea. The S-100-positive dendritic cells in the cholesteatoma revealed longer and more complexly branched processes than those in normal tissues. These findings suggest that the Langerhans' cells within the cholesteatomatous lesion are responsible for generating and maintaining the chronic immunological reactions in this disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454134
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  • 115
    Electronic Resource
    Electronic Resource
    An immunohistochemical method for the study of aminoglycoside ototoxicity in the guinea pig cochlea using decalcified frozen sections (1989)
    Springer
    European archives of oto-rhino-laryngology and head & neck 246 (1989), S. 161-164 
    Details
    ISSN: 1434-4726
    Keywords: Aminoglycosides ; Immunohistochemistry ; Ototoxicity ; Decalcified frozen sections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An immunohistochemical technique with decalcified frozen sections was used to study aminoglycoside ototoxicity. Decalcified guinea pig cochleas were cut with a fine blade parallel to the plane of the modiolus to facilitate the penetration of inclusion material and the manipulation of frozen sections. Light microscopy was carried out and additional frozen sections were employed for an immuno-electron microscopic study. Twenty-four hours after a single transtympanic injection of 10 mg gentamicin, there was a definite distribution of the drug in only type I hair cells of the ampullae as well as in both inner and outer hair cells along the length of the cochlea. In those animals treated intraperitoneally with 200 mg/ kg amikacin for 8 days, the drug was located in the outer hair cells of the cochlea, with a tendency to decrease from base to apex and in the inner hair cells towards the apex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456659
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  • 116
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720101
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  • 117
    Electronic Resource
    Electronic Resource
    The Conformation of Cycloartenol Investigated by NMR and Molecular Mechanics (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1-13 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloartenol (4), a natural plant sterol, was shown to be an effective membrane reinforcer; this was attributed to its conformation. We now present a conformational analysis of 4 by molecular modeling and NMR. Molecular modeling suggests that two conformations I and II coexist, differing mainly at the level of ring C, and of nearly equal energy, I and II each having ring A and B in a chair and half-chair conformation, respectively, with ring C 1,3-diplanar in I (solid-state structure as determined by X-ray crystallography) and in chair conformation in II. A complete assignment of the 1H- and 13C-NMR spectra of 4 and the entire coupling network in rings A and B is determined by various modern NMR techniques. The conformation of rings A and B thus determined is in agreement with conformations I and II. Low-temperature NMR experiments show a fast equilibrium between two conformations, presumably I and II. It is concluded, therefore, that the cyclopropane ring of 4 produces a flexibility at the level of ring C which may be important for the membrane properties.
    Additional Material: 8 Ill.
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    Palladium(0)-Catalyzed Cyclizations of Simple 1-Aryl-1,7-octadien-3-yl Acetates. Preliminary communicationPresented (W.O.) at the ‘3e Congrès national de la Société Française de Chimie’, Nice, September 5, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 14-16 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dienyl acetates 2 lacking a geminal disulfone or a malonate group cyclize selectively to (E)-l-methylidene-2-styrylcyclopentanes 4 in the presence of 7 mol-% of [Pd(PPh3)4].
    Additional Material: 1 Tab.
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  • 119
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    Über den Einfluss des Akzeptor-Teilchromophors bei Dimethin-merocyanin-Farbstoffen auf das Aggregationsverhalten in wässriger Lösung (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 17-28 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Influence of the Acceptor Part of the Chromophor of Dimethinemerocyanine Dyes upon the Aggregation Tendency in Aqueous SolutionA series of novel long-chain alkyl-dimethinemerocyanine dyes containing sulfonate groups is synthesized in good yield and their aggregation tendency in H2O and in organic solvent/H2O mixtures investigated. The merocyanine dyes 11 and 15 only exhibit an intense, red-shifted absorption band due to J-aggregation in H2O without addition of salt. The influence of cationic and anionic tensides and other compounds as urea, glucose, and polysaccharides upon the J-aggregation tendency is investigated.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720104
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  • 120
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    Generation and Trapping of TriafulveneFulvene, Fulvalenes, Part 55; Part 54: [1].Short communication: [2]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 29-40 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted methylidenecyclopropanes 12a-d, being easily available from 1,1-dibromo-2-(phenylthio)-cyclopropane (9a), are attractive precursors of triafulvene (2-methylidene-1-cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t-BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t-BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D-labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that H—C(2) of 12a-c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]-cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.
    Additional Material: 1 Ill.
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  • 121
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    A Nonconcerted Intramolecular Diels-Alder Reaction of Chiral Allenic-Acid Derivatives (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 59-64 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction between the chiral allenic acid (+)-(S)-1 and the carbodiimides 2a-d and the keten-imine 6 gives, under mild conditions, the tricyclic compounds 3-5, 7, and 8. Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.
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    URL: http://dx.doi.org/10.1002/hlca.19890720108
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  • 122
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    Konkurrenz von Endoperoxid- und Hydroperoxid-Bildung bei der Umsetzung von Singulett-Sauerstoff mit cyclischen, konjugierten Dienen. Teil I (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 51-58 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competition of Endoperoxide and Hydroperoxide Formation in the Reaction of Singlet Oxygen with Cyclic, Conjugated DienesRose-bengal-sensitized photooxygenation of (-)-(R)-α-phellandrene (1) in MeOH at room temperature yielded a complex mixture of products, contrary to previous reports describing cis-(3S, 6R)-epidioxy-p-menthene (2) and trans-(3R, 6S)-epidioxy-p-menthene (3) as the only products. The mixture was separated by prep. HPLC (silica gel, pentane/Et2O 9:1). Besides the known endoperoxides 2 (yield 39%) and 3 (26%), all those hydroper-oxides, which can be deduced from an ene reaction of 1O2 with 1, were isolated, i.e. 4β-p-mentha-2,5-dien-1β-yl hydroperoxide (4) (14%), 4β-p-mentha-2,5-dien-1α-yl hydroperoxide (5) (9%), (2R, 4R)-p-mentha-1(7), 5-dien-2-yl hydroperoxide (6) (2,1%), (2S, 4R)-p-mentha-1(7),5-dien-2-yl hydroperoxide (7) (1,5%) and (1R)-p-mentha-3,6-dien-yl hydroperoxide (8; 1,5%; Scheme 1). Furthermore, the constant cis/trans ratio for all diastereoisomeric pairs (2/2, 4/2, 6/2) was striking. With the help of the two possible conformers 1a and 1b of the starting material a model of a common first step for endoperoxide as well as for hydroperoxide formation is developed. A photooxygenation at -50° supports this model. The absolute value of the cis/trans ratio changes in the same way for the endoperoxides and the hydroperoxides.
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    Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 41-50 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).
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    Locoselective [4 + 2] Cycloadditions of Vinylindoles with Inverse Electron Demand: A new access of indolyl-substituted and annellated pyridazinesDedicated to Prof. Dr. C. H. Brieskorn (Würzburg, FRG) on the occasion of his 75th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 65-72 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Vinylindole (1a) and its donor- and acceptor-substituted (E)-derivatives 1b-e react highly locoselectively with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (3) to form the novel (indol-2-yl)-1,4-dihydropyridazines 4a and 7 as well as the heterocyclic annellated pyridazines 4b, 5, and 6. The reactions of the structurally related 3-vinylindoles 2a-e with 3 also gave rise to new indol-3-ylpyridazines 8, 9, and 10. The locoselectivities of these Diels-Alder reactions were controlled mainly by steric effects.
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    URL: http://dx.doi.org/10.1002/hlca.19890720109
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  • 125
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    Photochemistry of Thiophen-2(5H)-onesDedicated to Prof. Dr. O. E. Polansky on the occasion of his 70th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 83-92 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic evidence for the light-induced ring opening of thiophen-2(5H)-ones 1 in alcohols affording α, β-unsaturated mercapto esters 2 is presented. Regio-and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S-heterocycles 16 and 18, of 3-thiahex-5-enyl radicals 4 to (tetrahydrothien-3-yl)methyl radicals 6 and of (2,3-dihydrothien-3-yl)methyl radicals 30 (type 7, but-3-enyl radicals) to cyclopropane-methyl radicals 29 are discussed. Irradiation (λ 350 nm) of 1 in cyclohexane in the presence of 2,3-dimethylbut-2-ene affords [2 + 2] cycloadducts 14 albeit in very low yields.
    Additional Material: 1 Tab.
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  • 126
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    Electronic and Molecular Structure of the C8H10+· Valence Isomers 1,3,5-Cyclooctatriene+· and Bicyclo[4.2.0]octa-2,4-diene+· from their Electronic absorption Spectra in Freon (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 73-82 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular cations of 1,3,5-cyclooctatriene (COT+·) and bicyclo[4.2.0]octa-2,4-diene (BCO+·) can be observed intact in γ-irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements. This proves the superiority of the Freon-glass method for the generation of metastable primary cations. The electronic absorption (EA) spectra reveal a) that a previous analysis of the BCO+· electronic structure on the basis of the ultraviolet photoelectron (UP( spectrum of BCO was incomplete, and b) that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations. A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+·.
    Additional Material: 2 Ill.
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  • 127
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    Cyclization Studies with N-Mannich bases of 2-substituted indoles (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 93-100 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the indoles 7, 15, 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22, 23, and 24, respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26. In the presence of SnCl4, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27, 28) and eight-membered rings (→ 29) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series.
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    URL: http://dx.doi.org/10.1002/hlca.19890720112
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  • 128
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    Template-Dependent Incorporation of Spin-Labeled Thymidine Analogs into Viral DNA (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 110-116 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel pppUd analogs substituted at position C(5) with tethered nitroxide radicals is reported. It is shown that these analogs can serve as good substrates for E. coli DNA polymerase (Pol I) and T-4 DNA polymerase using lambda-phage DNA as template. The template-dependent incorporation of the substrates was established by radio-labeling and ESR experiments.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720114
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  • 129
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    Stereoselektive Synthesen von Taxan-Derivaten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 101-109 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Synthesis of Taxane DerivativesSubstituted racemic 4,8,12-trinortaxanes were prepared stereoselectively in several steps from the dienone 10. A variant of the de Mayo reaction with bicyclononenones 4 and cyclohexen produced the desired configuration at C(8) of the taxane framework. Retro-aldol cleavage of the tetracycle 5 led to the taxane skeleton 6. Stereoselective reduction followed by treatment with base afforded 7b. Hydrolysis of the acetal group and further reduction yielded 9 in which the relative configuration corresponds to the one of the natural products.
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    URL: http://dx.doi.org/10.1002/hlca.19890720113
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  • 130
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    Asymmetric Diels-Alder reactions: X-Ray crystal-structure analysis of [N-((E)-But-2-enoyl)bornane-10,2-sultam]tetrachlorotitaniumPresented (WO) at the Annual Congress of the Royal Society of Chemistry, Canterbury, April, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 123-130 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An X-ray diffraction analysis of the crystalline complex 2b (MLn — TiCl4) shows a chelation of the carbonyl O-atom and the upper SO2 O-atom by TiCl4, a slightly pyramidal N-atom, and a π -face-stereoselective shielding of the C(α)-Si face by the CH2(3) group. The Ti-atom is in a pseudo-octahedral environment.
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  • 131
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    Metal Complexes with Macrocyclic Ligands. Part XXVIIPart XXVI. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 131-138 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray structures of the Cu2+ complexes of 1,4,8,11-tetraazacyclotetradecane derivatives with an ethylpro-pionate and diethylphosphonate group, 5 and 6, respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one O-atom. In the case of 5, it is the carbonyl O-atom of the carboxylate group, whereas for 6 it is the phosphonyl O-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu2+ complexes with the 1,4,8,11-tetraazacyclotetradecanes 3-6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3-5 is proportional to the complex concentration and to [OH-] up to pH 13, whereas that of the phosphonate 6 is proportional to [OH-] up to pH 11.5, becoming independent of [OH-] at pH 〉 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra- or an intermolecular OH- attack and the results of the X-ray structure analyses.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720117
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    A New Method for the Preparation of (E)-3-Acylprop-2-enoic AcidsPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988.Dedicated to Prof. R. E. Ireland on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 117-122 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method for the preparation of (E)-3-acylprop-2-enoic acids ( = (E)-3-acylacrylic acids) of type II via acid-catalyzed isomerization of the corresponding 3-acylprop-2-ynal acetals of type I (Scheme 1) has been found. The described reaction gives a rapid and quite general access to these compounds known to exhibit a number of interesting biological activities. Some studies toward the elucidation of the reaction mechanism have been made, and a hypothetical mechanism is proposed.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720115
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    6-Thia-1-aza-5λ5-phosphabicyclo[3.2.0]hept-3-ene und Isothiocyanatophosphin-sulfide aus (Methylidenamino)phosphinen, Schwefelkohlenstoff und Acetylen- oder Ethylen-Derivaten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 139-146 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives(Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2. Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a, b, and acrylates yield isothio-cyanatophosphin-sulfides 5a-c. The structures of 4a and 5a are proven by an X-ray diffraction analysis.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720118
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    C45 und C50-Carotinoide. 6. Mitteilung5. Mitteilung, s. [1]. Synthese eines optisch aktiven cyclischen C20-Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotin) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 151-157 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C45- and C50-Carotenoids: Synthesis of an Optically Active Cyclic C20-Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotene)The synthesis of the optically active cyclic C20-building block (R, R)-15 and of the optically active C50-carotenoid (2R, 6R, 2′R, 6′R)-decaprenoxanthin (1) starting from (-)-β-pinene ((S)-2) is reported.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720120
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  • 135
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    Formation of the First Trimeric Monoterpenoid Indole Alkaloids (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 147-150 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3-hydroxy-14′-(3α″-tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′-(3α″-tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids.
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    URL: http://dx.doi.org/10.1002/hlca.19890720119
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    Polynuclear Iron and Rhodium Complexes of 7-Oxa[2.2.1]hericene (2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 158-164 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: μ-Carbonyl(Rh—Rh)di(η5-indenyl)[(2R,3S)-C,2,3,C-η-(2,3,4,5-tetramethylidenebicyclo[2.2.1]heptan-7-one)]]-dirhodium(I)(Rh—Rh) (7) and cis-μ-[(2R,3S,5R,6S))-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis[μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)] (8) have been prepared. Complex 7 reacts with Fe2(CO)9 in hexane/MeOH and gives cis-μ-[(2R,3S,5R,6S] (9), trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η: C,5,6, C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)-μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)-(tricarbonyliron) (10), and, μ-carbonyl(Rh—Rh)[(2R,3S)-C,2,3,C-η-(2,3-dimethyl-5,6-dimethylidenebicyclo-[2.2.1]hept-2-en-7-one)]di(η5-indenyl)dirhodium(I)(Rh—Rh) (11). Treatment of 7-oxa[2.2.1]hericene (4) with Fe2(CO)9 or (cyclooctene)2Fe(CO)3 gave a 1:2 mixture of cis-μ-[(2R,3S,5R,6S)-] (12) and trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis(tricarbonyliron)(13).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720121
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  • 137
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    Eine neue Aminoazirin-Reaktion. Bildung von 3,6-Dihydropyrazin-2(1H)-onen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 172-179 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-onesThe reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50-80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720123
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  • 138
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    Synthesis of the Oviposition-Deterring Pheromone (ODP) in Rhagoletis cerasi L. Preliminary communication (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 165-171 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the assignment of the configuration at C(8) and C(15) of the natural oviposition-deterring pheromone 1 in Rhagoletis cerasi L., the four possible stereoisomers of 1 are synthesized. By condensing the C6 building blocks (5R)-4 and (5S)-4 with the boron enolates of the C10 building blocks (4S)-13 and (4R)-13, followed by decarboxylative dehydration, all stereoisomers of 16 are available (Scheme 5). Glucosylation of 16 followed by formation of the taurin amide gives, after deprotection, the four stereoisomers (8R,15S)-1, (8R,15R)-1, (8R,15S)-1, and (8S,15S)-1 (Scheme 6).
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  • 139
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    Mitteilungen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 185-192 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720125
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  • 140
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    New Spermine Alkaloids from Aphelandra tetragona (VAHL) NEESDedicated to Prof. Dr. D. Gröger on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 180-184 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 18-O-Methylchaenorpine (1a) and iso-18-O-methylchaenorpine (1b) two novel stereoisomeric spermine alkaloids were isolated from the roots of Aphelandra tetragona (VAHL) NEES. Their structures were established by chemical and spectroscopic studies.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720124
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  • 141
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    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720201
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  • 142
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    1,5,7-Triazabicyclo[4.4.0]dec-5-en als Reaktionsmedium: Präparativ ergiebige einstufige Herstellung von Etioporphyrin aus Protoporphyrin (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 185-195 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,5,7-Triazabicyclo[4.4.0]dec-5-ene as Reaction Medium: An Efficient One-Step Formation of Etioporphyrine from ProtoporphyrineHeating the commercially available protoporphyrine (4) in molten 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 200° for 4 h under exclusion of O2 produces etioporphyrine (6) in 60-70% yield by bisdecarboxylation and concomitant reduction of the two vinyl groups. Mesoporphyrine (5) is bisdecarboxylated to 6 in over 80% yield under these conditions in TBD as well as in DBU as the reaction medium.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720202
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  • 143
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    The Chemistry of Thujone. Part XIV.Part XIII [1]. Synthesis of biologically active aryl terpenoid analogues (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 205-212 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Employing thujone-derived intermediates, a series of achiral (9a-d; Scheme 1) and chiral (11b and 11d; Scheme 2) terpene analogues related to the biologically active ‘terpenoid’ hybrids have been prepared. The stereochemistry of the key epoxidation reaction was established by correlation of the product 11b with the previously reported alcohol (R)-20 of known absolute configuration (Scheme 3).
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    URL: http://dx.doi.org/10.1002/hlca.19890720204
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  • 144
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    Vinyl Carbanions. Part 36.Part 35: [9]. Synthesis of 3-deoxy-D-manno-2-octulosonic acid (KDO) and derivatives (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 213-223 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The β-C-lithiated acrylamide 3A has been proven to be an ideal pyruvate β-carbanion equivalent useful in a highly diastereoselective KDO synthesis. The starting material 3 was prepared from pyruvate diethyl acetal in four convenient steps. Direct lithiation with 2 equiv. of LDA generated the dilithiated species 3A quantitatively. Reaction with 2,3:4,5-di-O-isopropylidene-D-arabinose (11) was highly D-manno-selective. The product 12 was obtained readily from the reaction mixture via crystallization. Ring closure to the butenolide 13, subsequent PhS-group removal with Bu3SnH and pyridinium bromide, and hydrogenolytic debenzylation afforded the known butenolide 19; this KDO precursor gives KDO in two convenient steps. Butenolide 19 was also transformed via two high-yielding steps into the 4,5:7,8-di-O-cyclohexylidene-KDO derivative 22, a valuable starting material for KDO α-glycoside syntheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720205
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  • 145
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    Colchicine models: Synthesis and Antitubulin Activity of 2′-Monosubstituted and 2′, 5-Disubstituted 2,3,4,4′-Tetramethoxy-1,1′-biphenyls. Synthesis of 4,4′, 5′, 6′-tetramethoxy-1,1′-biphenyl-2,3′-dicarboxylic acidThis paper is dedicated to our friend and colleague Dr. Tetsuji Kametani, Hoshi College of Pharmacy, Tokyo, Japan, who died on October 11, 1988 (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 196-204 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reductive amination of 2,3,4,4′-tetramethoxtybiphenyl-2-carbaldehyde (4) with MeNH2 afforded methylamine 5 (Scheme 1), Hydroxymethylation of amine 8, prepared similarly from 4 by reductive amination with benzylamine followed by N-methylation, afforded alcohol 12 which was converted the 5-methyl-substituted methylamine 14 by conventional chemical reactions (Scheme 2), Methylamine 14 was also obtained from ester 16 after hydroxymethylation to alcohol 17 and conventional manipulation of alcohol and ester functions (Scheme 2). Both amines 5 and 14 as well as the 2′, 5-dimethyl-substituted biphenyl 26 prepared from the dialdehyde 25 by a Wolff-Kishner reduction, did not show noteworthy activity in the tubulin binding assay or as inhibitors of tubulin polymerization (Table). However, the 2′ethyl-substituted biphebyl 11 prepared from 4 by reaction with MeLi followed by dehyderation and catalytic reduction of styrene 10 (Scheme 1) showed appreciable activity in both assays, coming close to that of known phenyltropolone models. The X-ray analysis of 14·HCl and 11 showed significant difference in the orientation of the rings with respect to one another (Fig.).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720203
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  • 146
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    Biosynthesis of Homoterpenes in Higher Plants (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 247-253 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In higher plants, the two homoterpenes 4,8-dimethyinona-1,3,7-triene (1) and 4,8,12-trimethyltrideca-1,3,7,11-tetraene (2) are synthesized from the regular terpene alcohols nerolidol and geranyllinalool by fragmentation into the homoterpene and butenone. The biosynthetic pathway is evidenced by conversion of (2H)nerolidol in Hoya purpureo-fusca, Magnolia liliiflora nigra, Robinia pseudoacacia, and Philadelphus coronarius.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720208
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  • 147
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    Sphinxolide, a 26-Membered Antitumoral Macrolide Isolated from an Unidentified Pacific Nudibranch (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 237-246 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that an unidentified nudibranch of Hawaiian waters contains a 26-membered macrolide, sphinxolide ((-)-1) with potent activity against the KB cell line. The structure of sphinxolide, a 2:1 mixture of (E/Z)-isomers at the formamide moiety, is established to be (-)-1 on the basis of extensive NMR and FAB-MS analysis, in combination with data for the products of mono- (→(-)-2) and diacetylation (→(+)-3).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720207
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  • 148
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    Synthesis of Aristotelia-Type Alkaloids.Part III: [1]. Part IV. Synthesis of (±)-aristoserratineDedicated to Prof. D. Arigoni on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 254-263 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A convergent diastereoselective synthesis of racemic aristoserratine ((±)-24) via an intramolecular iminium-ion cyclization is described. The pivotal imine (±)-19 was prepared by condensation of the two building blocks (± )-trans-8-amino-3-(2,6-difluorobenzyloxy)-1-p-menthene ((±)-11) and N-(p-methoxybenzenesulfonyl)-3-indo-leacetaldehyde (18) which were synthesized from (±)-trans-1-p-menthene-3,8-diol ((±)-7) and 3-indoleacetic acid, respectively. On the route to the target (±)-24, two previously unknown indole alkaloids have been characterized, namely (±)-‘anti’-hobartin-15-ol ((±)-22) and (±)-‘anti’-aristotelin-15-ol ((±)-23).
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720209
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  • 149
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    Syntheses of α, β-Epoxy Silyl Ketones (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 264-270 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the α, β-epoxy-acylsilanes 1 and 2 starting from the allylic silyl alcohols (E)- and (Z)-3, respectively, by epoxidation with t-BuOOH/VO(acac)2 followed by oxidation with Collins reagent (CrO3/pyridine) in up to 70% overall yields, is described. The acid-catalyzed rearrangement of the epoxy-silyl alcohols 4A + B und 5A + B led to the novel unstable diastereoisomeric α-silyl-β-hydroxy-aldehydes 9 and 10, respectively. The structure of 10 was established by X-ray crystal-structure analysis of the corresponding alcohol 11.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720210
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  • 150
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    Spectroscopic Studies of Cyclometallated Pd(II) and Pt(II) Complexes: Optical absorption and emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 224-236 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polarized optical absorption and emission (spectra, decay times) of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (thpy ≡ C(3′)-deprotonated form of 2-(2-thienyl)pyridine) at temperatures 1.9 K ≤ T ≤ 80 K are reported. The emission of [Pt(thpy)2] can be influenced strongly by applied magnetic fields (0 ≤ H ≤ 6 T). Depending on the central ions Pd and Pt, the lowest excited electronic states of the single complexes are ligand-centered (LC) states and metal-to-ligand charge transfer (MLCT) states, respectively. This difference leads to distinctly dissimilar properties of the emission of both compounds. The experimental data show that the emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] at T ≤ 30 K originates from several types of traps (defect states of symmetry 3B2-stabilized below the exciton band) with LC and MLCT character, respectively. In the Pt compound, the 3B2 is split by spin-orbit coupling into three states. The states B1′ and A2′, which determine the emission properties, are separated by Δv ∼ 13 cm-1. Both states can mix under the influence of an applied magnetic field yielding an increase of the emission intensity by a factor of ∼ 1.5 at H = 6 T.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720206
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  • 151
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    Total Synthesis of L-Allose, L-Talose, and derivatives.Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives (‘naked sugars’ [2]) as synthetic intermediates, Part IV. Part III, see [1]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 278-286 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (1S, 4R, 5S, 6S)-5-exo, 6-exo-(Isopropylidenedioxy)-7-oxabicyclo[2.2.1]heptan-2-one ((-)-1) was transformed with high stereoselectivity to L-allose. Similarly, enantiomer (+)-1 was transformed into L-talose. The ketones (+)-1 and (-)-1 were derived from furan and 1-cyanovinyl (1S)-camphanate and 1-cyanovinyl (1R)-camphanate, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720212
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  • 152
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    Highly Stereoselective Total Syntheses of 2,5-Anhydro-4-deoxy-D-ribo-hexonic Acid and of (1S)-1-C-(6-amino-7H-purin-8-yl)-1,4-anhydro-3-deoxy-D-erythro-pentitol (= cordycepin C)Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives (‘naked sugars’) as synthetic intermediates, Part V. Part III: [1]. Part IV: [2].Part of the planned Ph. D. thesis of F. G., University of Lausanne.Dedicated to Prof. Hans Dahn on the occasion of his 70th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 271-277 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly regio- and stereoselective monohydroxylation of the C=C bond of (+)-7-oxabicyclo[2.2.1]hept-5-en-2-one (8) was achieved via LiAlH4 reduction of the corresponding 5,6-exo-epoxy dimethyl acetal 9. The reaction gave exclusively (-)-(1R, 2R, 4S)-6,6-dimethoxy-7-oxabicyclo[2.2.1]heptan-2-exo-ol (10) which was transformed into 2,5-anhydro-3-O-benzyl-4-deoxy-D-ribo-hexonic acid (15) and 2,5-anhydro-4-deoxy-D-ribo-hexonic acid (6) via ozonolysis of (-)-(1R, 4S, 6R)-6-exo-benzyloxy-2-{[(tert-butyl)dimethylsilyl]oxy}-7-oxabicyclo[2.2.1]hept-2-ene (14). Cordycepin C (5) was derived from 6 and 4,5,6-triaminopyrimidine using CsF/DMF to generate the adenine heterocycle.
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    URL: http://dx.doi.org/10.1002/hlca.19890720211
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    Die absolute Konfiguration der Iridale und Cycloiridale unterschiedlicher HerkunftDr. G. Ohloff zum 65. Geburtstag mit den besten Wünschen gewidmet (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 287-294 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Absolute Configuration of Iridals and Cycloiridals of Different OriginNatural irones are known to occur in enantiomeric forms within Iris oils of different origin. They are formed by oxidative degradation of the cycloiridals (C31-triterpenoids) found in rhizomes of various Iris species. The absolute configuration of iridals from different varieties is determined by ozonolysis of the triterpenoids and comparison of their degradation products with authentic samples of known configuration. It is shown that the initial cyclization of squalene resulting in the formation of a monocyclic seco-ring-A iridal has the same stereo-chemical course throughout all Iris species studied. The subsequent cyclization of the homofarnesyl side chain of the iridals, however, produces cycloiridals with enantiomeric irone moieties within different subspecies of the sword lilies.
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    URL: http://dx.doi.org/10.1002/hlca.19890720213
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  • 154
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    Metal Complexes with Macrocyclic Ligands. Part XXVIII.Part XXVII: [1]. Structures and stabilities of the Cu2+ complexes with 1,4,7-triazacyclononane-1-acetic acid (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 307-312 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric study of the complexation of 1,4,7-triazacyclononane-l-acetic acid (1) with Cu2+ (I = 0.5 (KNO3), T = 25°) indicates the presence of the species [Cu(1)], [Cu(1)OH], [Cu(1)2], and [(Cu(1))2OH], the stability constants of which are determined. The two complexes [Cu(1)]ClO4 and [(Cu(1)2)OH]ClO4 were also characterized by X-ray structure analysis. In both cases, the Cu2+ ion is in a distorted square-pyramidal arrangement, penta-coordinated by the three N-atoms of the macrocycle, an O-atom of the carboxylate, and an additional O-atom either from a second carboxylate or from an OH-, acting as a bridge between two metal centres.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720215
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  • 155
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    Metal Complexes with Macrocyclic Ligands. Part XXIX.Part XXVIII: [1]. Structural and kinetic studies of two isomeric Cu2+ complexes with 1,4-dimethyl-8-[2-(2-pyridyl)ethyl]-1,4,8,11-tetraazacyclotetradecane (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 313-319 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and complexation properties of 1,4-dimethyl-8-[2-(2-pyridyl)ethyl]-1,4,8,11-tetraazacyclotetra-decane (2) are described. This ligand forms with Cu2+ two complexes, one of which has been characterized by X-ray structure analysis. The structural, spectral, and kinetic studies indicate that the two Cu2+ complexes are isomers with the macrocycle in the trans-III and trans-I configuration. The rate of the interconversion of the trans-I isomer to the thermodynamically more stable trans-III species is proportional to [OH-]. A mechanism for this reaction is proposed.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720216
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    Stereochemical Criteria Providing Unambiguous Experimental Evidence for the intermediacy of ion/molecule complexes in the generation of enolates from gaseous alkoxides. Short communicationDedicated to Prof. Josef Seibl on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 320-322 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The epimeric alkoxides 6a and 6b, generated in the gas phase by deprotonation of the stereospecifically deuterated isoborneols 5a and 5b, undergo loss of H2 and HD in a 1:1 ratio. This result, ruling out a concerted one-step process, establishes the intermediacy of an ion/molecular complex (‘solvated’ hydride ion) in the course of formation of enolates from the alkoxide anions in the gas phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720217
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  • 157
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    Neue Dimethinmerocyanin-Farbstoffe mit der (Sulfobutyl)benzothiazol-Gruppe als Donor-Teilchromophor und deren Aggregationsverhalten in wässriger Lösung (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 295-306 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel Dimethinemerocyanine Dyes with the (Sulfobutyl)benzothiazole Group as Donor Part of the Chromophor and their Aggregation Tendency in Aqueous SolutionA series of novel dimethinemerocyanine dyes with the (sulfobutyl)benzothiazole group as the donor part of the chromophor is synthesized in good yield and their aggregation tendency in H2O without addition of salt investigated. The merocyanine dye 2b only gives J-aggregation in H2O. The dyes 1a-f and 2a exhibit an intense, red-shifted absorption band due to J-aggregation in H2O in the presence of Me4NCl. In contrast, the dyes 1g and 2c-f show a slightly red-shifted absorption band. The degree of aggregation in H2O is investigated by ultracentrifugation of the representative 2e. Indeed, the slightly red-shifted absorption band in H2O is due to aggregation of ‘oligomers’ of the dye. Contrary to the aggregation of ‘polymers’ of dyes (J-aggregation), we suggest the term ‘K’ band for the slightly red-shifted absorption band. The hemicyanine dye 5 gives the same absorption band in MeOH and in MeOH/H2O 1:3. The dye 11 shows an absorption band in H2O that is probably blue-shifted because of negative solvatochromism. The merocyanine dye 13 gives H-aggregation in H2O.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720214
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  • 158
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    Models for Copper-Dioxygen Complexes: The chemistry of copper(II) with some planar tridentate nitrogen ligands (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 323-337 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1), 2,6-bis(l-methylbenzimidazol-2-yl)pyridine (mbzimpy, 2) 2,6-bis(benzothiazol-2-yl) pyridine (bzthpy, 3), 2,6-bis(benzoxazol-2-yl)pyridine (bzoxpy, 4), and 2,2′, 6′, 2″-terpyridyl (terpy, 5) is reported. Electronic and EPR spectra are consistent with the complexes [CuL]2+ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand-field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper. Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl- and OH- (provided that the ligand has no acidic protons) for all ligands except terpy. The reaction between [Cu(mbzimpy)]2+ and imidazole has been studied by potentiometric titration in MeCN/H2O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25°), and also the formation of an imidazolate-bridged dinuclear species.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720218
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  • 159
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    Synthesis of (-)-Conduritol C (1L-Cyclohex-5-ene-1,2,3/4-tetrol)Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5en-2-yl derivatives (‘naked sugars’ [1]) as synthetic intermediates, Part VI; Part V:[2]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 338-347 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (1R, 2R, 4R)-2-endo-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate ((-)-7) has been transformed into the all-cis-configurated 4L-4,5,6/0-trihydroxycyclohex-2-en-1-one derivatives (-)-12 and (-)-19. (-)-Conduritol C ((-)-3) was derived in a stereospecific manner from (-)-12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720219
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  • 160
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    Diels-Alder-Reaktionen mit 3-Cyclopropylidenprop-1-enyl-ethyl-ether als 1,3-Dien (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 348-352 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diels-Alder Reactions with 3-Cyclopropylideneprop-1-enyl Ethyl Ether as 1,3-DieneThe title compound undergoes readily Diels-Alder reactions with various dienophiles, especially with quinones. The resulting adducts constitute key intermediates in the synthesis of labdane diterpenoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720220
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  • 161
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    Synthese von (+)-Abscisinsäure (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 361-364 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (+)-Abscisic Acid.Starting from (4S)-4-hydroxy-2,6,6-trimethylcyclohex-2-enone (2), a short synthesis of the natural (+)-abscisic acid ((+)-1) has been accomplished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720222
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  • 162
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    Ein neuer Zugang zu 2,6,6-Trimethylcyclohexa-2,4-dienon aus 4-Oxoisophoron (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 365-369 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Access to 2,6,6-Trimethylcyclohexa-2,4-dienone from 4-Oxoisophorone2,6,6-Trimethylcyclohexa-2,4-dienone (1), a versatile starting material for the preparation of some carotenoids and several natural products, was efficiently (73% yield) prepared from oxoisophorone 3. After conversion of 3 to the alcohol 4 or the acetate 5, H2O was eliminated (4→1) under acidic distillative conditions, whereas AcOH could be eliminated (5→l) under Pd(O) catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720223
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  • 163
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    Neue Zugänge zu einigen aromatischen Retinoiden (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 370-376 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Approaches to Some Aromatic RetinoidsStarting from 2,3,5-trimethylphenol (2), two pathways to ethyl (all-E)-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethylnona-2,4,6,8-tetraenoate (1) and to some of its (Z)-isomers have been developed. The first one is based on a Pd(O)-catalyzed arylation of (Z)-3-methylpent-2-en-4-yn-l-ol (6) with 4-bromo-2,3,5-trimethylanisol (5). The acetylenic C15-alcohol 9 was transformed into the corresponding acetylenic phosphonium salt 10, which was catalytically hydrogenated to the olefinic Wittig salt. Wittig olefination led, then, to the (6Z, 8Z)- and (4Z, 6Z, 8Z)-isomers, 7 and 8, respectively. In a second approach, Friedel-Crafts reaction of 3-methylpent-l-en-4-yn-3-ol with the 2,3,5-trimethylanisol gave a C15-intermediate with a terminal C=C bond in the side chain. After deprotonation and reaction with a C5 aldehyd, the corresponding C20-intermediate could be isolated in high yield. Finally, further conversion led predominantly to the (all-E)-retinoid, accompanied by its (9Z)- and (13Z)-isomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720224
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  • 164
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    Synthesis of Gossypol AnaloguesDedicated to the memory of Professor Dr. Pierre Crabbé (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 353-360 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two gossypol analogues 2a and 2b were synthesized for biological evaluation as male contraceptive agents. The naphthol 8c was prepared by analogy with a known procedure starling from 3-isopropylcatechol (3). (t-Bu)2O2-Mediated phenolic coupling of 8c furnished the binaphthol 9c which, after pyrane ring closure, deprotection. and selective bisformylation with SnCl4/Cl2CHOCH3, gave the target compound 2a. The corresponding tetrahydroxy analogue 2b was prepared in a similar way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720221
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  • 165
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    Cyclometalated Compounds of Platinum(II) with two different C, N-aromatic ligands (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 377-382 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic route leading to bis-heteroleptic cyclometalated complexes is described. The complexes [2-(2′-thienyl)pyridinato-N, C-3′]{2-[3′-(trimethylsilyl)2′-thienyl]pyridinato-N, C3′}platinum(II) ([Pt(thpy) (TMS-thpy)]; I) and (l-phenylpyrazolato-N2, C2′)[2-(2′-thienyl)pyridinato-N, C3′]platinum ([Pt(Phpz)(thpy)]; II) are characterized by UV/VIS, NMR, and mass spectroscopy. Thermal and photochemical oxidative addition reactions yield two out of the 10 possible pairs of enantiomers of octahedral Pt(IV) compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720225
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  • 166
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    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720301
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  • 167
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    Mitteilungen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 401-402 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720228
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  • 168
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    The Radical Cations of Bicyclo[2.2.1]hepta-2,5-diene (8,9,10-Trinorborna-2,5-diene) and bicyclo[2.2.2]octa-2,5-diene (2,3-Dihydrobarrelene). An ESR and ENDOR studyPart 5 of ‘Applications of ENDOR Spectroscopy to Radical cations in Freon matrices’. Part-4: [1]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 383-390 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical cation of bicyclo[2-2.1]hepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1) in CF2ClCFCl2, and CF3CCl3 matrices and that of bicyclo[2.2.2]octa-2,5-diene (2,3-dihydrobarrelene; 2) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy. For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, methano-bridge, and bridgehead protons are -0.780 ±0.005, +0.304±0.002, and -0.049±0.002 mT, respectively. The hyperfine tensor for the methano-bridge protons is axial, Ax = +0.263 ± 0.002 and Ay = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = -0.594 ± 0.005, Ay= -0.913 ± 0.005, and Az = -0.834 ± 0.005 mT (x parallel to C—H- z parallel to 2pπ axis). For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are -0.68 ± 0.01, +0.162 ± 0.005, and -0.108 ± 0.005 mT, respectively. The hyperfine data for \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document} fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(π), of the two bonding ethene π-MO's.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720226
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  • 169
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    The Allylic Oxidation of Geraniol Catalyzed by Cytochrome P-450Cath., Proceeding with retention of configurationPresented in part at the ‘22nd Reaction Mechanisms Conference’, Pittsburgh, 12.6-16.6.88, at the ‘6th International Conference on Biochemistry and Biophysics of Cytochrome P-450’, Vienna, 3.7.-8.7.88, and at the meeting on the ‘Biocatalytic synthesis of Organic Compounds’, Saratoga Springs, NY, 8.-12.8.88.Dedicated to Prof. D. Arigoni on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 391-400 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Incubation of the geraniols (R)-(8-2H1)[8-3H1]-1 and (S)-(8-2H1)[8-3H1]-1 with microsomal cytochrome P-450Cath. from the subtropical plant Catharanthus roseus (L.)G. DON resulted in the formation of the chiral 8-hydroxygeraniols (S)-(8-2H1)[8-3H1]-2 and (R)-(8-2H1)[8-3H1]-2. Their absolute configuration was assigned on the basis of the 1H-decoupled 3H-NMR Spectra of the corresponding dicamphanates (S)-(8-2H1)[8-3H1]-9 and (R)-(8-2H1)[8-3H1]-9, of which the configurations are established in relation to the synthetic reference samples. The results clearly indicate retention of configuration during the allylic oxidation of 1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720227
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  • 170
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    Elektrochemische Decarboxylierung von L.-Threonin- und Oligopeptid-Derivaten unter Bildung von N-Acyl-N, O-acetalen: Herstellung von Oligopeptiden mit Carboxamid-oder Phosphonat-C-TerminusTeilweise in einer Kurzmitteilung erwähnt (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 401-425 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Electrochemical Decarboxylation of L-Threonine and Oligopeptide Derivatives with Formation of N-Acyl-N, O-acetals: Preparation of Oligopeptides with Amide or Phophonate C-TerminusDerivatives of α-amino acids with two stereogenic centers (cf. L-threonine) and of di-, tri-, and tetrapeptides are electrolyzed in MeOH or AcOH, with formation of N-acyl-N, O-acetals (1b-15b, 20b), in an anodic oxidative substitution of the COOH by an OR group. The amine ends of the oligopeptides may be benzyloxycarbonyl(Z)- or (tert-butoxy)carbonyl(Boc)-protected. With unprotected dipeptides, an electrolytic decarboxylative cyclization to imidazolidinones (18c, 19c) may also occur (in H2O/NH4OAc). The electrolyses are carried out in simple flasks with cooling jackets (‘undivided cell’), using constant current conditions and anodes of Pt or glassy C. The electrolyte is generated in situ by adding 10-20 mol-% of a tertiary amine. Mild acidic hydrolysis of electrolysis products thus obtained may lead to amino-acid amides or peptide amides (10c, 11c, 12c, 17c) with one amino acid less than the starting material. The N, O-acetals from L-threonine and the oligopeptides also react with organometallic nucleophiles such as Grignard compounds (→21-26, 29), with formation of products in which the original COOH group has been replaced by alkyl or allyl (sometimes even with moderate stereoselectivity). By treatment of the peptide-derived (open-chain) N, O-acetals with trialkyl or triaryl phosphites/TiCl4 the RO group is replaced by a phosphodiester group in a (non-diastereoselective) Michaelis-Arbuzov-type reaction (1d, 1e, 2d-9d, 5e). Thus, the two-step sequence of electrolysis and phosphonation converts an oligopeptide derivative to an analogue with a phosphonic-acid end group. The diastereoisomeric N-protected dimethyl and diethyl dipeptidephosphonates (also prepared from the corresponding diaryl esters by Ti(OR)4-mediated transesterification) could be separated by preparative HPLC (SiO2, Lichrosorb Si 60, 10 μm); the dextrorotatory isomers of 1d-3d were assigned L, D-, the laevoratory ones L, L-configuration by hydrolysis to and identification of the known amino and aminophosphonic acids. The results described demonstrate a new simple route leading, from a given oligopeptide, to pure peptide analogues of known configuration.
    Notes: No abstract.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720302
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  • 171
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    Acid-Catalyzed Cyclization Reactions of Substituted Acetylenic Ketones: A new Approach for the Synthesis of 3-Halofurans, Flavones, and StyrylchromonesPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 447-456 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetylenic acetals of type I (Scheme 1) and acetylenic ketones of type III (Scheme 1), 37 and 38 (Scheme 7) are versatile synthetic precursors for the synthesis of various heterocycles by acid-catalyzed cyclization reactions. By this way, substituted 3-halofurans of type II and IV (Scheme 1) and flavones and styrylchromones (Scheme 7) can be synthesized in good-to-excellent yields. The high degree of regioselectivity in the synthesis of the 3-halofurans (Scheme 4) is the result of the regioselective β-addition of HX (X = Cl, Br, I) to the acetylenic aldehyde and acetylenic ketone moieties. A possible mechanism is depicted in Scheme 5. Since 3-halofurans can easily be metalated and substituted, this approach constitutes a new synthesis of highly substituted furans.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720305
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  • 172
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    Stoffwechselprodukte von Mikroorganismen. 253. Mitteilung252, Mitteilung. Hormaomycin, ein neues Peptid-lacton mit morphogener Aktivität auf Streptomyceten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 426-437 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hormaomycin, a Novel Peptide Lactone with Morphogenetic Activity on StreptomycesA culture identified as Streptomyces griseoflavus (strain W-384) has been found to produce a novel peptide-lactone antibiotic designated hormaomycin (6). The empirical molecular formula of the compound is established to be C55H69ClN10O14. The constituent amino acids of the antibiotic are suggested to be allothreonine (1; 1), isoleucine (2; 1), 3-methyl-phenylalanine (3; 2), and, for the first time identified from a natural source, 4-[(Z)-prop-1-enyl]-proline (4; 1) and 3-(2-nitrocyclopropyl)-alanine (5; 2). The amino acids were delivered by acidic hydrolysis and assigned by high-resolution- GC/MS analysis (after transformation to derivatives) in combination with extended 2D-NMR experiments of the antibiotic itself. From the latter, it became plausible that the N-terminus of the peptide chain is acylated by a Cl-containing derivative of 1H-pyrrol-2-carboxylic acid. Hormaomycin is active against some Gram-positive bacteria. In addition, the antibiotic exhibits potent aerial mycelium-inducing activity and effects the production of antibiotics.
    Notes: No abstract.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720303
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  • 173
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    Novel Trinor-eremophilanes (Dendryphiellin B, C, and D), Eremophilanes (Dendryphiellin E, F, and G), and Branched C9-Carboxylic Acids (Dendryphiellic Acid A and B) from the Marine Deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 438-446 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further investigation of global extracts from cultures of the marine deuteromycete Dendryphiella salina leads to the isolation of three novel trinor-eremophilanes esterified by branched C9-carboxylic acids, dendryphiellin B(= (+)-(1R*,2S*,7R*,8aR*)-1,2,6,7,8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*, 2E, 4E)-6-hydroxy-6-methylocta-2,4-dienoate; (+)-2), dendryphiellin C (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7,8,8a-hexa-hydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6S, 2E, 4E)-6-methylocta-2,4-dienoate; (+)-3)), and dendryphiellin D (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7(8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*,2E,4E)-6-(hydroxymethyl)octa-2,4-dienoate; (+)-4). An intact eremophilane, dendryphiellin E (5), and its ethanolysis product dendryphiellin F whose absolute configuration is represented by structural formula (+)-6 are also isolated from the above extracts. Dendryphiellin E exists as an open form 5a in equilibrium with a closed form 5b. A similar equilibrium exists between the open form 8a and the closed form 8b of a non-esterified eremophilane, dendryphiellin G (8), which is isolated too from the above extracts and proves structurally related to the cyclic portion of 5. Finally, the free, branched C9-carboxylic acids dendryphiellic acid A ((+)-9) and B ((+)-10) which correspond to side chains of the above esterified terpenes are also isolated from the above extracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720304
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  • 174
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    Eine neue Azepinring-Synthese (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 457-463 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Azepine-Ring SynthesisA new one-step synthesis of an azepine ring is described. The 2H-pyran-2-one ring of methyl cumalate (8) or cumalaldehyde (2) upon reaction with an 1-aminoacryl derivative, e.g. 1 or 6, is opened with subsequent decarboxylation to give a 1-aminobutadiene derivative that undergoes an electrocyclic ring closure to the azepine ring (Schemes 1 and 2).
    Notes: No abstract.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720306
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  • 175
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    New Hyperforin Derivatives from Hypericum revolutum VAHL with Growth-Inhibitory Activity against a Human Colon Carcinoma Cell LinePresented in part at the 36th Annual Congress on Medicinal Plant Research, Freiburg im Breisgau, FRG, 12-16th September, 1988, and at the Meeting of the Swiss Chemical Society, Bern, 21st October, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 464-471 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crude petroleum-ether extract of the root bark of Hypericum revolutum VAHL (Guttiferae) exhibited in vitro growth-inhibitory activity against the Co-115 human colon carcinoma cell line. Activity-guided fractionation of this extract resulted in the isolation of two new hyperforin derivatives 1 and 2. The structure of 1 (hyperevolutin A) was established by X-ray analysis as the 4-hydroxy-8-exo-methyl-5,7-exo-bis(3-methylbut-2-enyl)-1-(2-methyl-1-oxopropyl)-8-endo-(4-methylpent-3-enyl)bicyclo[3.3.1]non-3-ene-2,9-dione. The structure of the homologue 2 was deduced by comparison of its UV and 1H- and 13C-NMR spectra with those of 1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720307
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  • 176
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    Asymmetric Diels-Alder Reaction of 1-Methoxybuta-1,3-diene with (2R)-N-Glyoxyloylbornane-10,2-sultam (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 482-486 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from sultam 1, the chiral dienophile (2R)-N-glyoxyloylbornane-10,2-sultam (4) was readily prepared. Non-catalyzed atmospheric- and high-pressure as well as [Eu(fod)3]-promoted [4 + 2] cycloadditions of 1-methoxy-buta-1,3-diene (5) to chiral dienophile 4, leading with high asymmetric induction to 6-methoxy-3,6-dihydro-2H-pyran-2-yl derivatives 6-9, are described. The extent and direction of asymmetric induction in these reactions were established by 1H-NMR analysis and chemical correlation, respectively. Stereochemical models for both non-catalyzed and [Eu(fod)3]-promoted reactions are proposed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720310
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  • 177
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    5,10:8,9-Disecosteroids (= Steroklastanes): A new type of modified steroidsDr. Günther Ohloff on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 608-623 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermolysis of steroidal 5α, 8α- peroxides of type 3a-d generates as major products the corresponding diseco compounds containing a 14-membered ring instead of the standard A-B-C-ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β-unsaturated ketones of type 4, formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer-Villiger oxidation to give, as final products, the 15-membered cyclic epoxyenol lactones of type 20 and 21. The structures of the various products were determined by 1H- and 13C-NMR spectroscopy. The conformations of the 14- and 15-membered rings were established by X-ray structure analyses of 7 and 21a. A reaction mechanism for the above transformations is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720320
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  • 178
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    Thermal and Photochemical Reactions of 1,2-Annelated Barrelenes and Hydrobarrelenes in the presence of transition-metal carbonyls (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 648-652 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [Co2(CO)8]-mediated retro-Diels-Alder reaction of the annelated barrelenes 1 afforded the 1H-indol-2(3H)-one derivatives 3 (Scheme 1), while the hydrobarrelene 4a, under the same conditions, was converted to the anilide 6 (Scheme 2); 4b remained unaffected. The direct irradiation of 1 led to the annelated cyclooctatetraenes 7 (Scheme 3). On irradiation in the presence of excess of [Fe(CO)5], 1a, 1b, and 4a gave the tricarbonyliron complexes 8, 9, and 11, respectively (Schemes 3 and 4); under these conditions, 4b was inert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720404
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  • 179
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    A Simple and Efficient Method for the Preparation of Binaltrorphimine and Derivatives and determination of their K opioid antagonist selectivity (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 675-677 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bimorphinans 1 (binaltrorphimine), 3, and 7 have been prepared by treatment of the parent morphinan-6-ones naltrexone (5), naloxone (4), and dihydrocodeinone (6), respectively, with N-methylhydrazine sulfate in AcOH at room temperature. Compound 3 showed opioid antagonist potency and selectivity for K receptors which were somewhat lower in comparison to 1.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720408
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  • 180
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    Synthèse d'une sonde biotinylée à bras clivable allongé pour l'isolement des récepteurs de l'angiotensine II (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 678-689 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of a Biotinylated Probe with an Extended Cleavable Arm for Angiotensin II Receptors PurificationWe have synthesized a new biotinylated probe for angiotensin II receptors studies: biotinyl-NH(CH2)2—SS—(CH2)2—CO-Gly-∊ Ahx-[Ala1, Phe(4N3)8]angiotensin II (5). This molecule can be photoactivated through an arylazido group. 1H-NMR studies suggest that it adopts an extended conformation which should allow a simultaneous recognition of both streptavidin and hormone receptor. It has a good affinity for receptors (Kd = 1 nM) and hence is a promising tool in their detection (autoradiography, gold-, ferritin-, enzyme-, or fluorescent streptavidin derivatives) and separation (cell sorting, affinity chromatography). It can be monoiodinated (°6) at its tyrosine residue without a significant loss of affinity. Its extended cleavable arm allows an easy recovery of the ‘probe-receptor’ complex from streptavidin. An HPLC monitoring of the synthesis is described, particularly of the segment coupling 1 + 2 in presence of (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP). This method can be used as well for synthesis of the D-Phe8 derivative that has antagonist properties.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720409
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  • 181
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    Synthesis of 11-Oxaestrogens via Dye-Sensitized Photo-oxygenation of a 9,11-Didehydroestrone Derivative (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 725-730 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 3-methoxy-1 1-oxaestrone (13) has been synthetized from estrone (3) following an approach that involves the ring-C fragmentation of the estrogenic skeleton by dye-sensitized photo-oxygenation of the properly C(17)-protected 9,11-didehydroestrone derivative 6 as the key step. The C(13)-side-chain degradation of the 9-oxo-9,11-seco-aldehyde 7 followed by reduction to the 9β, 12-diol 10 and further cyclization yields the 11-oxaestrogenic skeleton. By this procedure, 13 is obtained in 9 steps from 3 with a non-optimized overall yield of ca. 15%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720412
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  • 182
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    Photo-oxygenation of Styrenic Estrogens: Product characterization and kinetics of the dye-sensitized photo-oxygenation of 9,11-didehydroestrone derivativesPhotochemical Reactions, Part 23. Part 22: [1] (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 715-724 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dye-sensitized photo-oxygenation of 3-hydroxyestra-1,3,5(10), 9(11)-tetraen-17-one (8) gives a complex mixture from which only the 1,4-endo-peroxide 10 can be isolated in low yield. In contrast, the 3-methoxy derivative 9 yields the C-seco-aldehyde 11 as a major product, suggesting that 1,2-dioxetane is a primary photo-oxygenation intermediate. As the electron-donating character of the substituent at C(3) decreases in the sequence 12 (R = PhCO), 13 (R = Ac), and 14 (R = Ts), the rate constant in substrate disappearance becomes drastically smaller as compared with 8 and 9, and no photoproducts are detected. The results are rationalized by means of electronic and conformational factors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720411
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  • 183
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    Synthèse énantiospécifique des acides (+)-(2R)- et (-)-(2S)-éthyl-6-dihydro-3,4-méthyl-2-oxo-4-2H pyranecarboxylique-5 (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 731-737 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiospecific Synthesis of (+)-(2R)- and (-)-(2S)-6-Ethyl-3,4-dihydro-2-methyl-4-oxo-2H-pyran-5-carboxylic AcidThe two enantiomers (-)-(2S)- and (+)-(2R)-6-ethyl-3,4-dihydro-2-methyl-4-oxo-2H-pyran-5-carboxylic acid ((S)- and (R)-7) have been synthesized from (+)-(3S) and (-)-(3R)-3-hydroxybutanoates, respectively (Scheme 1). By reduction and decarboxylation, the tetrahydro-2H-pyranols (2R, 4R, 6S)- and (2S, 4S, 6R)-13, respectively, were obtained with an enantiomeric excess of ≥ 93%.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720413
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  • 184
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    Pteridines. Part XLIPart XL, see[1]. Synthesis and properties of 6,7,8-trimethyl-4-thiolumazine (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 738-743 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first representative of the 8-substituted 4-thiolumazine series has been synthesized. In a sequence of reactions, 4,6-dichloropyrimidin-2-(1H)-one (1) is first converted into 4-chloro-6-(methylamino)pyrimidin-2(1H)-one (6), then the Cl-atom displaced by the thioxo group (→7) followed by a coupling reaction with 4-chlorophenyldiazonium chloride to introduce the necessary N-function into the 5-position (→ 9; Scheme 1). Reduction of the p-chlorophenylazo group leads to the 6-(methlyamino)-4-thiouracil-5-amine (10) which on condensation with diacetyl gives 6,7,8-trimethyl-4-thiolumazine (8). The physical properties of 8 are compared with the 2-thio analog and 6,7,8-trimethyllumazine indicating that 8 possesses the highest acidity and the longest UV absorption.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720414
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  • 185
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    Studies on the Biosynthesis of Spirostaphylotrichin A (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 774-783 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Incorporation of 14C-labelled acetate and amino acids as well as of [1-13C]-, [2-13C]-, and [1,2-13C2] acetate, L-[methyl13C] methionine, [2,3-13C2] succinate, and L-[2,3-13C2] aspartate into spirostaphylotrichin A (1) by Staphylotrichum coccosporum demonstrates that the building blocks of 1 are 5 units of acetate/malonate, 1 unit of methionine, and a C4-dicarboxylic acid. The latter is most likely aspartate and derived from the citric-acid cycle. Using [2-13C, 2-2H3] acetate as a precursor, the starter unit of the polyketide chain was identified.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720418
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  • 186
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    New Spirostaphylotrichins from Staphylotrichum coccosporum (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 784-792 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isolation and structure elucidation of the new spirostaphylotrichins B (2), C and D (3/4), F (5), Q (6), and R (7) are described. Compounds 2 and 3 are artefacts formed during the isolation of the metabolites from the cultures. The absolute configuration of spirostaphylotrichin A (1) has been determined by CD spectroscopy.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720419
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  • 187
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    Diazotisation Mechanism of Heteroaromatic Amines. Diazotisation of 2-aminothiazole as an equilibrium (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 800-805 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate of diazotization of 2-aminothiazole was measured in 65 to 75% (w/w) aqueous H2SO4. The kinetic solvent isotope effect of the diazotization in 72% D2SO4/D2O was determined (kH/kD = 5.8 ± 0.2). These data are consistent with a mechanism in which the 2-aminothiazole, protonated at the ring N-atom, but not at the NH2 group, is attacked by the NO+ ion. The reaction does not go to completion, but to an equilibrium. The equilibrium concentration of the diazonium ion was determined in 30,50,70, and 90% (w/w) H2SO4 at three initial concentration of reagents (0.001,0.01, and 0.1m). The final concentrations of the reagents and the diazonium ion are consistent with a reversible process. This is the first diazotization for which quantitative evidence for equilibration has been found. In the very large range of acidities used (Ho = -1.73 to -9.01), it was not possible to calculate meaningful equilibrium constants that are independent of the acidity.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720421
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  • 188
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    Struktur/wirkung-Beziehungen bei Geruchsstoffen mit dem Bicyclo[2.2.2.]octan-GerüstHerrn Dr. Günther Ohloff mit den besten Wünschen zum 65. Geburtstag gewidmetAuszugsweise vorgetragen an ‘The Conference on Terpene Chemistry’, 25.4.1986, Grasse, und am ‘19th International Symposium on Essential Oils and Other Substrates’, 9.19.1988, Greinfensee/Dübendorf, Schweiz. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 806-810 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure-Activity Relationships of Odorants with a Bicyclo[2.2.2]octane SystemThe synthesis of the olfactory interesting homonojigikualcohol 2 and of its epimer 10 leads to the keto alcohols 6a, b and 7a, b as intermediates. The latter have OH and C=O groups (an AH/B system) fixed at the rigid bicyclic nucleus at different distances (2.8 and 4.7 Å) and confirm Ohloff's rule for odoriferous properties which is based on this distance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720422
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  • 189
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    Solubilization of Peptides in Non-polar Organic Solvents by the Addition of Inorganic Salts: Facts and ImplicationsDedicated to Prof. Gerhard Schröder on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 857-867 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solubility of open-chain peptide derivatives (12 examples) in non-polar, ether-type organic solvents may be greatly increased by addition of salts (LiCl, LiBr, LiI, LiBF4, LiClO4, NaI, MgBr2 CaBr2, ZnCl2) or of titanates (Ti(OEt)4, Ti(OCHMe2)4). Examples are reported (Tables 2-6) in which this solubilizing effect leads to peptide concentrations more than one-hundred-fold those in the absence of salt (cf, Boc—Ala—Gly—Gly—Gly—OH in THF from 2g·1-1 to ≥ 300 g·1-1 with 6 equiv. of LiCl), 1H-NMR Spectra of one of these solutions are reported (Fig. 1). There are no indications for epimerizations of stereogenic centres on the peptide backbone. Possible applications of these solutions in peptide chemistry are discussed.
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    URL: http://dx.doi.org/10.1002/hlca.19890720502
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  • 190
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    Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]ironPart of the planned Ph. D. thesis of Edia Bonfantini, Ecole Polytechnique Fédérale de Lausanne. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 906-916 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene-l-methanol (7) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe2(CO)9] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene (8) led to the formation of a 1.7:1 mixture of ‘trans’ (19, 21, 22) vs. ‘cis’ (20, 23, 24) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron (25) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron (26). The structures of products 19 and of its exo (21) and endo (22) [Fe(CO)3(1,3-diene)]complexes) and 20 (and of its exo (23) and endo (24) (Fe(CO)3(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron (21). In the latter, the Fe(CO)3(1,3-diene) moiety deviates significantly from the usual local Cs symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η3-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720506
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  • 191
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    Synthesis of Chiral 12-Phenyl(2H)dodecanoic Acids: Useful metabolic probes for the biosynthesis of 1-alkenes from fatty acids (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 917-928 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of chiral 12-phenyi(2H)dodecanoic acids as metabolic probes for the evaluation of the stereo-chemical course of the biosynthesis of 1-alkerses from fatty acids in plants and insects is described. The diastereoisomeric (2R, 3R)- or (2S, 3S)-12-phenyl(2,3-2H2)dodecanoic acids 11 are obtained in high chemical and optical yield (〉97% e.e.) from the readily available (E)-12-phenyl(2,3-2H2)dodec-2-enoic acid (10) or (E)-12-phenyldodec-2-enoic acid (10a) by microbial reduction with wet packed cells of Clostridium tyrobutyricum in either 2H2O or H2O buffer. (2R)- and (2S)-12-phenyl(2-2H)dodecanoic acids 9 (〉97% e.e.) are accessible from the allylic alcohol 6 via Sharpless epoxidation with (+)-L- or (-)-D-diethyl tartrate, Synthetic routes to the (E)- and (Z)-11-phenyl(1-2H) undec-1-enes 16 and 16a as reference compounds are also included.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720507
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  • 192
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    Photochemical Reactions 150th Communication149th Communication: [1]. Wavelength Dependence of the Photochemistry of 7-Methyl-β-ionone (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 933-942 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The wavelength dependence of the photolysis of 7-methyl-β-ionone ((E)-1) was investigated. Irradiation of (E)-1 with light of λ 〉 347 nm leads primarily to (E/Z)-isomerization followed by transformation to the tricyclic enol ether 3 as the only secondary photoproduct. On photolysis of (E)-1 with light of shorter wavelength (λ 〉 280 nm or λ = 254 nm), however, a series of other products was formed (via a) photocyclization of the dienone chromophore (→ 5), (b) photo-enolization (→8), and (c) a 1,5-sigmatropic H-shift (→ (E/Z)-7). For the structure elucidation of the new products, 7-[13C]methyl-β-ionone ((E)-[7-methyl-13C]-1) was prepared and irradiated furnishing the corresponding 13C-labelled photoproducts.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720509
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  • 193
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    Catechol-O-methyltransferase-Inhibiting Pyrocatechol Derivatives: Synthesis and Structure-Activity Studies (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 952-968 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Nitro- and 3-cyanopyrocatechols bearing electron-withdrawing substituents at C(5) have been found to inhibit the enzyme catechol-O-methyltransferase. Structure-activity studies are discussed on the basis of the pharmocological data of 50 compounds (cf, Chapt. 4, Tables 1-7). Some 3-nitro-5-aroylpyrocatechols (Type A2, Table 1) fulfil the requirements for a clinical candidate, being orally active, specific, reversible, and relatively short-acting. The chemical work involved is illustrated by describing a choice of exemplary syntheses, dealing with compounds 9, 11, 14, 18, 22, 24, 25, 35, 41, and 42 (Chapt. 5, Schemes 1-10).
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720511
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  • 194
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    Glycosylidene Carbenes a new approach to glycoside synthesis. Part 1. Preparation of glycosylidene-derived diaziridines and diazirinesPresented at the ‘197th ACS National Meeting’, Dallas, Texas, 9th-14th April 1989, Abstr. Carb 9. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1371-1382 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach towards the synthesis of glycosides based upon a (formal) insertion of glycosylidene carbenes into O—H bonds is presented. The synthesis and characterization of the glycosylidene-derived diazirines 25-28, precursors of glycosylidene carbenes, are described. The diazirines were prepared by the rapid, high-yielding oxidation of the diaziridines 20 and 22-24 with I2/Et3N. The diaziridines, the first examples of C- alkoxy-diaziridines, were formed in high yields by the reaction of the [(glycosylidene)-amino]methanesulfonates 14 and 17-19 with a saturated solution of NH3 in MeOH. The diazirines are highly reactive compounds, losing N2 at room temperature or below. The reaction of the gluco-configurated diazirine 25 with i-PrOH yielding a mixture of the α- and β-D-glucosides 29 and 30 illustrates the potential of glycosylidene-derived diazirines as a new type of glycosyl donors.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720626
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  • 195
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    An Electrochemical Variant in the Syntheses of Exaltone® and muscone: Anodic fragmentation of α, β-unsaturated tosylhydrazonesDedicated to Dr. Günther Ohloff on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1383-1389 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring enlargement of bicyclo[10.3.0]pentadec-1(12)-en-13-one p-toluenesulfonylhydrazone into cyclopentadec-4-yn-l-one was accomplished under mild and controlled anodic oxidation conditions. The mechanism of this fragmentation is reconsidered.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720627
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  • 196
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    Structure-Activity Relationship in Ambergris-Type Woody Odorants possessing a hydronaphthalene skeletonDedicated to Dr. G. Ohloff on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1390-1399 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of methyl hydronaphthyl alcohols, formates, acetates, and ketones were prepared and their odour properties evaluated. Minor structural changes, even opposite to the osmophoric group, were found to have major effects on the odour. 13C—NMR shift assignments of the hydronaphthyl derivatives are presented.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720628
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  • 197
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    New Irone-Related Constituents from the essential oil of Iris germanica L.Dedicated to Dr. G. Ohloff on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1400-1415 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Twenty irone-related compounds 1-20 containing from 10 to 16 C-atoms have been identified for the first time in commercial Iris oil of Moroccan origin (Iris germanica L.). Most of the structures and the absolute configurations of natural 6, 16, and 17 are corroborated by partial synthesis. The organoleptic properties of some of the new constituents are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720629
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  • 198
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    Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1428-1434 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ESR and ENDOR studies have been carried out on the radical cations obtained consecutively by reaction of trans-10b, 10c-dimethyl-10b, 10c-dihydropyrene (4) with AlCl3 in CH2C12. The primarily formed \documentclass{article}\pagestyle{empty}\begin{document}${\bf 4}^{+ \atop \dot{}}$\end{document} rearranges at 253 K to the radical cation(s) of 1,6- (5a) and/or 1,8-dimethylpyrene (5b). At 323 K, the spectra of \documentclass{article}\pagestyle{empty}\begin{document}${\bf 5a}^{+ \atop \dot{}}$\end{document}/\documentclass{article}\pagestyle{empty}\begin{document}${\bf 5b}^{+ \atop \dot{}}$\end{document} are replaced by that of the highly persistent radical cation of 1,3,6,8-tetramethylpyrene (6). Surprisingly, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 6}^{+ \atop \dot{}}$\end{document} is also the only observable paramagnetic product resulting from a treatment of 4,5,7,8- (1), 4,7,13,16- (2), and 4,5,12,13-tetramethyl[2.2]paracyclophane (3) with AlCl3 in CH2Cl2 at 353 K. The structures of the intermediates in the rearrangement [\documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 3}^{+ \atop \dot{}}$\end{document}] → \documentclass{article}\pagestyle{empty}\begin{document}${\bf 6}^{+ \atop \dot{}}$\end{document} are discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720631
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  • 199
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    [4 + 2]-Cycloadditionen von α, β- ungesättigten hydrazonen. Teil3Teil 2: [1]. Isothiazolo[4,5-b]pyridin-3(2H)-on-1,1-dioxide (= 4-azasaccharine) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1435-1443 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [4 + 2] Cycloaddition of α, β-Unsaturated Hydrazones: Isothlazolo[4,5-b]pyridin-3(2H)-on 1,1-Dioxides (= 4-Azasaccharine Derivatives)The [4 + 2] cycloaddition of α, β -unsaturated hydrazones of type 1 (1-azabuta-1,3-dienes) with isothiazol-3(2H)-on 1,1-dioxide derivatives 10 affords, depending on the solvent used, picolinamides 15 or 17, 4,7-dihydro-4-azasaccharine 14 or 4-azasaccharine derivatives 16 (Scheme 4). The course of the reaction is mainly influenced by the substituent R of the dienophile 10.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720702
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  • 200
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    Bildung von 5,6-Dihydro-1,3(4H)-thiazin-4-carbonsäure-estern aus 4-Allyl-1,3-thiazol-5(4H)-onen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1639-1646 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of Methyl 5,6-Dihydro-l, 3(4H)-thiazine-4-carboxyiates from 4-Allyl-l, 3-thiazol-5(4H)-ones.The reaction of N-[1-(N, N-dimethylthiocarbamoyl)-1-methyl-3-butenyl]benzamid (1) with HCl or TsOH in MeCN or toluene yields a mixture of 4-allyl-4-methyl-2-phenyl-1,3-thiazol-5(4H)-one (5a) and allyl 4-methyl-2-phenyl-1,3-thiazol-2-yl sulfide (11; Scheme 3). Most probably, the corresponding 1,3-oxazol-5(4H)-thiones B are intermediates in this reaction. With HCl in MeOH, 1 is transformed into methyl 5,6-dihydro-4,6-dimethyl-2-phenyl-1,3(4H)-thiazine-4-carboxylate (12a). The same product 12a is formed on treatment of the 1,3-thiazol-5(4H)-one 5a with HCl in MeOH (Scheme 4). It is shown that the latter reaction type is common for 4-allyl-substituted 1,3-thiazol-5(4H)-ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720724
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