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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1505-1509 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Functionally Substituted Pyridines by Hetero-Diels-Alder Reaction with Inverse Electron DemandInverse type hetero-Diels-Alder reaction of functionally substituted α,β-unsaturated carbonyl compounds with enol ethers afforded “exo/endo” mixtures of the γ-acetoxy-substituted dihydropyrans 2, 5, and 8, respectively. Deacetylation, oxidation of the hydroxy group, alcohol elimination, and ammonia treatment provided the γ-pyridones 14-16, which upon O-alkylation were transformed into the pyridines 21, 22, and 25, respectively, possessing electron-donating ring substituents. The structures were assigned by 1H-NMR data and by comparison with structural isomers.
    Notes: Die inverse Hetero-Diels-Alder-Reaktion zwischen funktionell substituierten α,β-ungesättigten Carbonylverbindungen und Enolethern lieferte die γ-Acetoxy-substituierten Dihydropyrane 2, 5 und 8 als “exo/endo”-Gemische. Durch Desacetylierung, Oxidation der Hydroxygruppe, Alkohol-Eliminierung und Behandlung mit Ammoniak wurden daraus die γ-Pyridone 14-16 gewonnen, die durch O-Alkylierung in die Pyridine 21, 22 und 25 mit elektronenliefernden Ringsubstituenten übergeführt wurden. Die Strukturen wurden mit Hilfe von 1H-NMR-Daten und durch Vergleich mit Strukturisomeren zugeordnet.
    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: De novo Synthesis of Carbohydrates and Related Natural Products, 321). - The Inverse Type Hetero-Diels-Alder Reaction for the Synthesis of Partial Structures of Polyketide Natural ProductsInverse type hetero-Diels-Alder reaction of the 1-oxa-1,3-diene 1a as heterodiene with (Z) ethyl 1-propenyl ether as dienophile afforded in an endo-specific cycloaddition reaction the persubstituted 3,4-dihydro-2H-pyran 2a. Convenient regio- and diastereospecific transformations furnished the 2-deoxy-2-methyl-manno-hexopyranoside 8; oxidation of this compound and subsequent Wittig reaction, hydrogenation, and acetylation gave diastereoselectively the 2,4-dideoxy-2,4-dimethyl-talo-hexopyranoside 12.
    Notes: Die inverse Hetero-Diels-Alder-Reaktion des 1-Oxa-1,3-diens 1a als Heterodien mit (Z)-Ethyl-1-propenylether als Dienophil lieferte in einer endo-spezifischen Cycloaddition das persubstituierte 3,4-Dihydro-2H-pyran 2a. Durch einfache regio- und diastereo-spezifische Umwandlungen wurde das 2-Desoxy-2-methyl-manno-hexopyranosid 8 erhalten, das durch Oxidation, Wittig-Reaktion, Hydrierung und Acetylierung diastereoselektiv zum 2,4-Didesoxy-2,4-dimethyl-talo-hexopyranosid 12 führte.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0170-2041
    Keywords: 1,3-Dienes, 1-oxa, chiral ; α-Methoxyacrylates as heterodienophiles ; Asymmetric Induction ; Hetero-Diels-Alder reaction, inverse-type ; N-Acetylneuraminic Acid ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inverse-type hetero-Diels-Alder reaction-based diastereoselective synthesis of 3-deoxy-2-glyculosonates is performed with the help of chiral carbon substituents in the 2-position of the 1-oxa-1,3-diene required as heterodiene. This is demonstrated for the synthesis of the selectively O-protected and the O-unprotected N-acetylneuraminic acid derivatives 21 and 22, respectively. Thus, the heterodiene 10, obtained from D-mannose in high overall yield, affords with methyl α-methoxy-acrylate as heterodienophile preferentially the stereoisomer 11 with β-D-ribo configuration. Phenylthio group removal, diastereospecific 5-hydroxy and 6-hydrogen transfer, and then stereocontrolled introduction of the acetamino group into the 5-position furnished compound 21 with the required D-glycero-D-galacto configuration. Structural proof comes from the transformation into the known N-acetylneuraminic acid derivative 22.
    Type of Medium: Electronic Resource
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