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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 232-239 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A Procedure for an α-Glycoside Synthesis of 3-Amino-2,3,6-trideoxyhexopyranoses from GlycalsThe anomeric mixture of the hex-2-enopyranosyl azides 2 und 3, either of which adopts an equilibrium with the 3-azidoglycals 5 and 6, reacts with cyclohexanol and N-iodosuccinimide to give the 3-azido-2-iodo derivatives having α-D-altro- (4) and α-D-manno configuration (9). By reductive work-up and subsequent acetylation the synthesis of 3-acetylamino-2,3-dideoxy-α-glycosides of D-ribo (7) and of D-arabino structure (8) is achieved. By a corresponding reaction sequence starting with di-O-acetyl-L-rhamnal (10) a three step synthesis of both α-L-ristosaminide (16) as well as α-L-acosaminide (17) is realized.
    Notes: Das Anomerengemisch der Hex-2-enopyranosylazide 2 und 3, die jeweils mit den 3-Azidoglycalen 5 bzw. 6 im Gleichgewicht stehen, wird mit Cyclohexanol und N-Iodsuccinimid zu den 3-Azido-2-iod-Derivaten mit α-D-altro- (4) und α-D-Manno-Konfiguration (9) umgesetzt. Deren reduktive Aufarbeitung nebst Acetylierung ermöglicht die Synthese von 3-Acetylamino-2,3-didesoxy-α-glycosiden der D-ribo- (7) und der D-arabino-Struktur (8). In einer vergleichbaren Reaktionssequenz wird aus Di-O-acetyl-L-rhamnal (10) in nur drei Stufen die Synthese des α-L-Ristosaminids (16) sowie des α-L-Acosaminids (17) realisiert.
    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: Building Units of Oligosaccharides, LVIII.  -  Regioselective Glycosylation at 3′—OH or 4′—OH of Lactose Using Different Catalyst SystemsThe lactose derivative 4 with unsubstituted 3′—OH and 4′—OH groups makes regioselective glycosylation reactions possible depending on the chosen type of catalyst system. In the presence of silver triflate, 4 reacts in homogenic phase with the phthalimido bromide 1 to yield the β(1→3)-glycosidically linked trisaccharide 5. The same compounds give in heterogenic phase with silver silicate regioselectively the β(1→4)-glycosidically linked trisaccharide 7. In the presence of silver silicate, 4 reacts with the azido halide 2 to yield in heterogenic phase regioselectively the β(1→4)-glycosidically linked product 17. In homogenic phase with silver perchlorate, however, the azido halides 2 and 3 yield the α-glycosidically linked products, following the in situ anomerization procedure.
    Notes: Mit dem Lactose-Derivat 4 mit unsubstituierten 3′—OH— und 4′—OH—Gruppen ist eine regioselektive Glycosylierung je nach Wahl des Katalysator-Systems möglich. Mit dem Phthalimidobromid 1 reagiert 4 in homogener Phase bei Gegenwart von Silbertriflat regioselektive zum β(1→3)-glycosidisch verknüpften Trisaccharid 5. Die gleichen Verbindungen reagieren dagegen in heterogener Phase mit Silbersilicat regioselektive zum β (1→4)-glycosidisch verknüpften Trisaccharid 7. Umsetzung von 4 mit dem Azido-Halogenid 2 ergibt bei Gegenwart von Silbersilicat in heterogener Phase ebenfalls regioselektive das β(1→4)-glycosidisch verknüpfte Produkt 17. In homogener Phase bei Gegenwart von Silberperchlorat liefern dagegen die Azido-Halogenide 2 und 3 nach dem in-situ-Anomerisierungsverfahren α-glycosidisch verknüpfte Produkte.
    Type of Medium: Electronic Resource
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