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  • Organic Chemistry  (3,406)
  • ddc:330
  • 1980-1984  (3,406)
Collection
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 616-624 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural modifications of multifidene (1), viridiene (2) and ectocarpene (5) led to the synthesis of eleven new pheromone components or imitatin substances mostly by Grignard alkylation of cyclopentene and cycloheptadiene synthons. A new lactone α,ω dienol conversion is reported.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 640-653 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The He(Ia) photoelectron (PE) spectra of the (E,E)-, (E,Z)- and (Z,Z)-isomers of the title compound have been recorded to obtain information about their conformation in the gas phase. For a valid correlation with the PE data of other dienes it is necessary to take the potentials V(ϕ) for internal rotation and the corresponding conformer population densities P (ϕ) into account, as well as the rather complicated way wy in which the π-1 ionization energy gap ΔI(ϕ) depends on the direct π-orbital interaction and the long-range ‘through-space’ interaction between the semi-localized methyl-group orbitals and the π-orbitals. These factors being taken into account, the mean twist angles, ϕ, compatible with the PE-spectroscopic results are ϕ (E,E) ≍ O° ± 30°, ϕ (E,Z) ≍ 80° or 110° within ± 15°, and ϕ (Z,Z) ≍ 85° to 105°. These results are in rough agreement with electron diffraction data by Traetteberg [15], other spectroscopic results and, for the (E, E)- and (Z,Z)-isomers, internal rotation potentials V(ϕ) previously calculated by Roth [17]. On the other hand the potential V (ϕ) proposed for the (E,Z)-isomer does not seem to be compatible with our findings.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The olefins 2, 7, 11, and 19, have been reduced using catalytic amounts of cob(I)alamin(I(I)). During a slow saturation, the catalyst is able to differentiate the two diastereotopic faces of the endocyclic double bonds in 11 (t1/2 4 h,. cf. Scheme 3) are reduced much faster. A rationalization of the data can be obtained formulating tertiary alkylcobalamins as intermediates. Of the oxime 6 (cf. Scheme 2) and the p- bromobenzoate 23 (cf. Scheme 5) the structures have been determined by X-ray analysis.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural Elucidation of Niphimycin, Part 3. Identity of Scopafungin and Niphimycin I. Position of the Malonyl Residue of Niphimycin and CopiamycinThe identity of scopafungin with niphimycin I was proven by spectroscopic and chromatographic methods and by common degradation products. The position of the malonyl residue in niphimycin I (9) and in copiamycin (14) was deduced by 1H-NMR spin-decoupling experiments of a degradation product (10).
    Additional Material: 2 Tab.
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses, Chemical and Electrical Properties of Tetrathiafulvalene with a 1,6-Methano[10]annulene Moiety and of Chalcogendiimide-DerivativesThe synthesis of the tetrathiafulvalene 6 has been described: the reaction of 1 with the benzenedithoil 2 yielded the bis-dithioacetal 3 of 1,6-methano[10]annulene-dicarbaldehyde 1. The oxidation of 3 in the presence of HBF4 in Et2O yielded the salt 4, elimination of a hydride anion with triphenylmethylium tetrafluoroborate the salt 5, and elimination of a proton in 5 with Et3N the tetrathiafulvalene 6 with a 1,6-methano[10]annulene moiety. The spectroscopic and electrochemical properties of 6 are described, and also the syntheses and properties of charge-trasnfer complexes 7 and 8, including the properties of electric conductivity of 7 and 8. the syntheses of 9-13 are reported and also their spectroscopic properties.
    Additional Material: 1 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 765-769 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Voltammetric Investigations on the Oxidation Step of Symmetrical Triazacarbocyanine Dyes in Acetonitrile SolutionThe oxidation behaviour of twelve symmetrical triazacarbocyanine dyes with different heterocycles in MeCN (containing tetrabutylammonium perchlorate) has been investigated by means of dc-, ac- and cyclic triangular wave voltammetry. The oxidation mechanism has been found to be of the type ec, with the electrochemical step being reversible to irreversible. Oxidation potentials and transfer coefficients have been measured (E1/2 1.60 to 2.12 V vs. Ag/AgCl) and compared with known properties of carbocyanines. The effect of substituents X has been studied on the compounds 1,3-diethyl-2-[3-(1,3-diethyl-5-X-benzimidazolin-2-ylidene)-1-triazeno]-5-X-benzimidazolium tetrafluoroborate ((1a(X)) and 3-ethyl-2-[3-ethyl-5-X-Δ4-1,3-thiazolin-2-ylidene)-1-triazeno]-5-X-1,3-thiazolium tetrafluoroborate (1g(X)), and ρ-values of 0.425 and 0.565 V, respectively, have been found.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 947-952 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselective synthesis of (+)- and (-)-cis-2-methyl-4-propyl-1,3-oxathine 8 and 9 form (E)-2-hezen-1-ol (1) as common starting material is described. The two enantiomeric forms exhibit different organoleptic properties.
    Additional Material: 2 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1003-1011 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plectranthons A, B, C, and D. Diterpenoid Phenanthrene-1,4-diones from Leaf-glands a Plectranthus sp. (Labiatae)The following structures of four new 1,4-phenanthraquionones, isolated in minute amounts from the coloured leaf-glands of a Plectranthus sp. obtained from the borders of Lake Kiwu2, Rwanda, are proposed: plectranthon A (1; 3-hydroxy-5, 7,8-trimethyl-2-(2-propenyl)phenanthrene-1, 4-dione), plectranthon B (2; 2-(2ξ-acetoxypropyl)-3-hydroxy-5,7,8-trimethylphenanthrene-1,4-dione), plextranthon C (3; 3-hydroxy- 7,8-diemethyl-2-(2-propenyl)phenanthrene-1,4-dione), and plectranthon D (4; 3-hydroxy-7,8,10-trimethyl-2-(2-propenyl)phenanthrene-1,4-dione). 2-(2ξ-Hydroxypropyl)-3,6-dihydroxy-5,7,8-trimethylphenanthrene-1,4-dione (11), a compound very similar to 1-4, was prepared by a Wagner-Meerwein, rearrangement of coleon E (5). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C20-phenanthrenes of diterpenoid origin.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 535-556 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclitol Reactions, VIII. - Synthesis of Enantiomerically Pure (+)-Lycoricidine from D-GlucoseThe synthesis of enantiomerically pure (+)-lycoricidine (1) from D-glucose is described. The key reaction step is the addition of the aromatic anion 31 to the nitroolefin sugar 18 which gives the branched-chain sugars 32 and 33. After liberation of the aldehyde function of 32 and intramolecular aldol addition, 32 yields the lacton 35, a branched-chain nitroinositol with muco configuration. Reduction of the nitro group yields the amine 38 and rearrangement the lactam 40. Selective benzoylation to 43 followed by dehydration gives 47 which allows deblocking to (+)-lycoricidine (1). (+)-Lycoricidine (1) and its triacetate 49 are identical with the natural product.
    Notes: Die Synthese von enantiomerenreinem (+)-Lycoricidin (1) aus D-Glucose wird beschrieben. Der Schlüsselschritt der Reaktionsfolge ist die Addition des aromatischen Anions 31 an den Nitroolefin-Zucker 18, der zu den verzweigten Nitrozuckern 32 und 33 führt. Durch intramolekulare Aldolreaktion ist nach Freisetzung der Aldehydgruppe in 32 über 34 das Lacton 35 erhältlich, das einen verzweigten Nitroinosit der muco-Konfiguration enthält. Die Reduktion der Nitrogruppe in 35 führt zur Aminoverbindung 38, deren Lactongruppierung in das Lactam 40 umgelagert werden kann. Das aus 40 durch selektive Benzoylierung erhältliche Tribenzoat 43 ergibt durch Eliminierung von Wasser das Derivat 47, aus dem freies (+)-Lycoricidin (1) gewonnen werden kann. (+)-Lycoricidin (1) und dessen Triacetat 49 sind mit dem Naturprodukt identisch.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 575-584 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aminonucleosides, XI. - Bis(trimethy ammonio) Derivatives of AdenosineA five-step reaction starting from the aminonucleosides 1a or 1b yields the bis(trimethylammonio) derivatives 3′-trimethylammonio-6-[3-(trimethylammonio)propylamino]-3′-deoxyadenosine (8a) and 5′-trimethylammonio-6-[2-(trimethylammonio)ethylamino]-5′-deoxyadenosine (8b), respectively. The new compounds are biologically active and have muscle relaxing properties.
    Notes: Ausgehend von den Aminonucleosiden 1a und 1b wird in einer Fünf-Stufen-Reaktion die Synthese der Bis(trimethylammonio)-Derivate 3′-Trimethylammonio-6-[-3-(trimethylammonio)propylamino]-3′-desoxyadenosin (8a) und 5′-Trimethylammonio-6-[2-(trimethylammonio)ethylamino]-5′-desoxy-adenosin (8b) beschrieben. Die neuen Verbindungen sind biologisch aktiv und besitzen muskel-relaxierende Eigenschaften.
    Additional Material: 2 Tab.
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