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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 14 (1864), S. 301-303 
    ISSN: 1615-6110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Reactivity of Silicon Transition Metal Complexes, V. The Modified Alkali Salt Elimination Method  -  a General Procedure for the Synthesis of Silicon Transition Metal CompoundsThe heterogeneous reaction of the sodium carbonylmetallates Na[Fe(CO)2π-C5H5], Na[M(CO)3π-C5H5] (M=Mo, W), and Na[Mn(CO)5] with various halo- and organohalosilanes leads to the formation of the corresponding silyl complexes. The new compounds are characterized by spectroscopy and the chemical properties are described. The results of a decomposition study of the trimethylsilyl-VIB transition metal complexes are discussed in connection with former synthetic experiments. Exchange reactions of these species with heterosiloxanes can be used for a qualitative estimation of relative metal-metalloid bond reactivity.
    Notes: Die Umsetzung der komplexen Metallate Na[Fe(CO)2π-C5H5], Na[M(CO)3π-C5H5] (M=Mo, W) und Na[Mn(CO)5] mit verschiedenen Halogen- und Organohalogensilanen führt in heterogener Reaktion zu den Silylkomplexen dieser Metalle. Die neuen Verbindungen werden spektroskopisch charakterisiert und ihre chemischen Eigenschaften beschrieben. Die Ergebnisse einer Zerfallsstudie der Trimethylsilyl-VIB-Übergangsmetallkomplexe werden im Zusammenhang mit früheren Syntheseversuchen diskutiert. Der Verlauf von Austauschreaktionen der gleichen Verbindungen mit Heterosiloxanen (Ge, Sn) ermöglicht eine qualitative Abschätzung der Reaktivität der Metall- Metalloideinheit.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition Metal Substituted Phosphanes, Arsanes, and Stibanes, XXIII. Stable Transition Metal Dimethylarsanes Bearing a Tricarbonyl(cyclopentadienyl)chromium, -molybdenum or -tungsten SubstituentBy the interaction of (CH3)2AsCl with [C5H5(CO)3M]Na or C5H5(CO)3M - Si(CH3)3 stable carbonyl(cyclopentadienyl)metal dimethylarsanes of the formula C5H5(CO)3M - As(CH3)2 (M = Cr, Mo, W) (1 - 3) are obtained for the first time. Their thermal treatment in the solid state yields [(CH3)2As]2 and [C5H5(CO)3M]2, in solution with loss of CO the cyclic species [C5H5(CO)2M - As(CH3)2]2 4a (Mo), 4b (W) are formed. Under photolytic conditions in addition to 4a, b the aggregation products trans-C5H5(CO)2[C5H5(CO)3M - As(CH3)2]M - As (CH3)2 (5a, b) and [trans-C5H5(CO)2M - As(CH3)2]x (6a, b) are isolated. Alkyl halides and (CH3)3SiI readily convert 1 - 3 into the cationic complexes [C5H5(CO)3M - As(CH3)2R]X (R = CH3, CH2C(O)C6H5, CH2Si(CH3)3, Si(CH3)3; X = Br, I) (7a - f). With chlorine or bromine the extremely labile dihalogen adducts C5H5(CO)3M - As(CH3)2Hal2 (8a - c) are formed, which rapidly decompose to (CH3)2AsHal and C5H5(CO)3MoHal or C5H5(CO)3WH. HCl, CF3CO2H, (CH3)3SnH, Na/Hg, CH3MgI, and (CH3)3PCH2 cleave the transition metal-arsenic bond under very mild conditions.
    Notes: Durch die Reaktion von (CH3)2AsCl mit [C5H5(CO)3M]Na oder C5H5(CO)3M - Si(CH3)3 werden erstmals stabile Carbonyl(cyclopentadienyl)metall-dimethylarsane der Form C5H5(CO)3M - As(CH3)2 (M = Cr, Mo, W) (1 - 3) erhalten. Ihre thermische Behandlung in Substanz liefert [(CH3)2As]2 und [C5H5(CO)3M]2, in Lösung unter CO-Eliminierung die cyclischen Verbindungen [C5H5(CO)2M - As(CH3)2]2 4a (Mo), 4b (W). Unter photolytischen Bedingungen werden zusätzlich zu 4a, b die Aggregationsprodukte trans-C5H5(CO)2[C5H5(CO)3M - As(CH3)2]M - As(CH3)2 (5a, b) und [trans-C5H5(CO)2M  -  As(CH3)2]x (6a, b) isoliert. Alkylhalogenide und (CH3)3SiI überführen 1 - 3 glatt in die kationischen Komplexe [C5H5(CO)3M - As(CH3)2R]X (R = CH3, CH2C(O)C6H5, CH2Si(CH3)3, Si(CH3)3; X = Br, I) (7a - f). Mit Chlor oder Brom werden die extrem labilen Dihalogenaddukte C5H5(CO)3M - As(CH3)2Hal2 (8a - c) gebildet, die rasch zu (CH3)2AsHal und C5H5(CO)3MoHal bzw. C5H5(CO)3WH zerfallen. HCl, CF3CO2H, (CH3)3SnH, Na/Hg, CH3MgI und (CH3)3PCH2 spalten die Übergangsmetall-Arsenbindung unter sehr milden Bedingungen.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 2835-2851 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Reactivity of Silicon Transition Metal Complexes, VI. Halogenation of Transition Metal Substituted Silicon HydridesTreatment of the complexes LnM—Si(CH3)2H, LnM—SiCh3ClH and Ln—SiCl2H [LnM = Fe(CO)2π-C5H5 M(CO)3 π-(5H5) (M=Cr, Mo, W), Mn(CO)5] with CCl4 and CBr4 yields the halogenated compounds LnM—Si(CH3)2Cl, LnM—Si(CH3)2Br, LnM—SiCH3Cl2 and LnM—SiCl3. This procedure represents in some cases the only access to the halosilylsubstituted derivatives. With the exception of metallate reactions involving extremely reactive silanes, e. g. chlorosilacyclobutanes, this route proves to be superior to the „direct“ method. A quantitative study of the exchange rate suggests a free radical mechanism for the halogenation of the metalsubstituted silicon hydrides. The properties of the new silicon transition metal compounds are described.
    Notes: Die Umsetzung der Hydrogensilyl-Komplexe LnM—Si(CH3)2H, LnM—SiCh3ClH und LnM—SiCl2H [LnM = Fe(CO)2π-C5H5 M(CO)3 π-(5H5)(M = Cr, Mo, W), Mn(CO)5] mit CCl4 und CBr4 führt unter Wasserstoff/Halogen-Austausch zu den halogenierten Produkten LnM—Si(CH3)2Cl, LnM—Si(CH3)2Br, LnM—SiCH3Cl2 und LnM—SiCL3. Der Weg über die HSi-Verbindungen stellt teilweise den einzigen Zugang zu halosilylierten Metallkomplexen dar und ist mit Ausnahme der Metallatreaktion besonders reaktiver Siliciumkomponenten wie z. B. der Halosilacyclobutane dem „direkten“ Verfahren überlegen. Eine quantitative Studie der Austauschgeschwindigkeit macht für die Halogenierung metallsubstituierter Hydrogensilane eine Radikalkettenmechanismus wahrscheinlich. Die Eigenschaften der neu hergestellten Silicium-Übergangsmetallverbindungen werden beschrieben.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 84 (1972), S. 538-539 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Cyclopeptides from Trichoderma polysporum (LINK EX PERS.) RIFAI: Cyclosporins B, D and ECyclosporins represent a new group of biologically active metabolites produced by Trichoderma polysporum (LINK EX PERS.) RIFAI and other fungi imperfecti. The structures of the main components, cyclosporins A (1) and C(3) have been determined as neutral cyclic oligopeptides composed of 11 amino acids, among them a new C9-amino acid [2-4]. In addition, three minor metabolites, cyclosporins B, D and E, have now been isolated and characterized. Chemical investigation, spectroscopic evidence and X-ray analysis led to the structural formulae of cyclosporins B (2) and D (4). Both compounds have the same sequence of amino acids as cyclosporin A (1), with the exception of L-α-aminobutyric acid, replaced in cyclosporin B (2) by L-alanine and in cyclosporin D (4) by L-valine, respectively. Cyclosporins undergo a characteristic intramolecular N,O-acyl migration to furnish the corresponding basic isocompounds. The antifungal activities of cyclosporins are reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isolation of lignan J, C28H34O13, a new compound from the roots and rhizomes of American Podophyllum peltatum L. and Indian P. emodi Wall. is described. Lignan J is easily cleaved to desoxypodphyllotoxin and D-glucose. By degradation of its penta-phenylurethane, the structure of lignan J has been deduced as the 1β-D-glucopyranosylester of desoxypodophyllinic acid. It is suggested that glucose esters of this type may act as intermediates in the biogenesis of lignans.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 1247-1255 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Structure of Cyclosporin CThe structure of cyclosporin C (2), a minor antifungal metabolite from Trichoderma polysporum (Link ex Pers.) RIFAI has been elucidated. Hydrolytic cleavage and spectroscopic evidence show that cyclosporin C is a neutral oligopeptide of 11 amino acids linked together in a 33-membered ring. Cyclosporin C (2) differs from the main metabolite cyclosporin A (1) [2] [4] only by containing L-threonine in the place of L-α-aminobutyric acid as has been shown by the conversion of 2 into 1. 13C-NMR. spectra and study of molecular models suggest that cyclosporin C (2) has the same molecular conformation as 1, which is best described as a twisted β-pleated sheet held together in a conformationally stable form by intramolecular hydrogen bonding.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclosporin A, a Peptide Metabolite from Trichoderma polysporum (LINK ex PERS.) Rifai, with a remarkable immunosuppressive activityTwo antifungal metabolites, cyclosporins A and C, were isolated from a strain of Trichoderma polysporum (LINK ex PERS.) Rifai. Cyclosporin A, the main component, has the molecular formula C62H111N11O12 as deduced by NMR. and mass spectra. Hydrolytic cleavage of cyclosporin A furnished 11 amino acids as fragments, among them an artefact of a new C9-amino acid. The amino acid sequence was determined by Edman degradation of iso-cyclosporin A, a basic rearrangement product formed from cyclosporin A by N, O-acyl migration. In an independent investigation an X-ray analysis of the iodo derivative 10 was performed (see the following paper). On the basis of the chemical, spectroscopic and crystallographic evidence the complete structure of cyclosporin A was elucidated as the neutral cyclic oligopeptide 1. Cyclosporin A and C show remarkable immunosuppressive and antiphlogistic activities in several pharmacological models.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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