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  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Luteochrome isolated from the tubers of a white-fleshed variety of sweet potato (Ipomoea batatas LAM.) has been shown by HPLC, 1H-NMR and CD spectra to consist of a mixture of (5R,6S,5′R,8′R)- and (5R,6S,5′R,8′S)- 5,6:5′,8′-diepoxy-5,6,5′,8′-tetrahydro-β,β-carotene (1 and 2, resp.). Therefore, its precursor is (5R,6S,5′R,6′S)-5,6:5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene (4). This is the first identification of luteochrome as a naturally occurring carotenoid and, at the same time, gives the first clue to the as yet unknown chirality of the widespread β,β-carotene diepoxide. These facts demonstrate that the enzymic epoxidation of the β-end group occurs from the α-side, irrespective of the presence of OH groups on the ring.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Addition von Crotylchrom(II) und Dilithium-propionat an (R)-2,3-O-Isopropylidenglycerinaldehyd: sterischer Ablauf und Anwendung in einer formalen Synthese von (+)- und (-)-δ-MultistriatinBei der Addition an (R)-2,3-O-Isopropylidenglycerinaldehyd (1) zeigt das Chrom(II)-Salz 4a von Crotylbromid hohe enantiofaciale und geringe diastereofaciale (d. h. Cram-)Selektivität, während sich Dilithium-propionat (9) entgegengesetzt verhält. Die Addukte 5, 7 und 10 lassen sich zu einer formale Synthese beider Antipoden des Insektenpheromons δ-Multistriatin (30) verwenden.
    Notes: The chromium(II) salt 4a of crotyl bromide adds to (R)-2,3-O-isopropylideneglyceraldehyde (1) with high enantiofacial and low diastereofacial (i. e. Cram) selectivity, whereas dilithium propionate (9) shows the opposite behaviour. The adducts 5, 7, and 10 can be used in a formal synthesis of both enantiomers of the insect pheromone δ-multistriatin (30).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1540-1547 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese von kationischen und mesoionischen Derivaten von 1,2,4-Triazolo[3,4-b][1,3,4]-thiadiazolen über Iminophosphorane1,2,4-Triazolo[3,4-b][1,2,4]thiadiazolium-Salze 4 werden nach zwei allgemeinen Methoden aus 4-Amino-2,4-dihydro-2-methyl-5-(methylthio)-3H-1,2,4-triazol-3-thion (1) dargestellt. Nach der ersten Methode werden Aryliden-Derivate 2 erhalten, die mit Phosphorpentachlorid cyclisieren; die zweite Methode basiert auf der Reaktion des Iminophosphorans 5 mit Säurechloriden. Die Umsetzung von 5 mit Acylisothiocyanaten führt direkt zu den mesoionischen Verbindungen 6.
    Notes: Two general methods are reported for the preparation of 1,2,4-triazolo[3,4-b][1,2,4]-thiadiazolium salts 4 from 4-amino-2,4-dihydro-2-methyl-5-(methylthio)-3H-1,2,4-triazol-3-thione (1). The first one involves the initial formation of arylidene derivatives 2 which undergo cyclization by the action of phosphorus pentachloride; the second one is based on the reaction of the iminophosphorane 5 with acyl chlorides. The reaction of 5 with acyl isothiocyanates led directly to the mesoionic compounds 6.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 299-304 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktionen mit stabilen Phenoxyl-RadikalenWasserstoffabstraktion bei aktiven Methyl-, Methylen- und Methinverbindungen mit 4-Methoxy-2,6-diphenylphenoxyl erwies sich als geeignetes Verfahren zur Synthese von Ethern des 4-Methoxy-2,6-diphenylphenols. Bei dreifach aktivierten Methinverbindungen erfolgt hauptsächlich Dimerisierung (C—C-Verknüpfung) der durch H-Abstraktion gebildeten Radikale.
    Notes: Hydrogen abstraction from activated methyl, methylene, and methine compounds with 4-methoxy-2,6-diphenylphenoxyl proved to be a useful approach for the synthesis of the corresponding ethers of 4-methoxy-2,6-diphenylphenol. With triple activated methine compounds dehydrogenation mainly results in C—C dimerization of the radicals.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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