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- W2019298510 abstract "Methyl-3,4-anhydro-6-desoxy-α-L-arabino-hex-5-enopyranosid1) (3a) und das β-Anomere 3b reagieren bei Raumtemperatur glatt mit Ammoniak in Methanol, sowie mit Azid und Cyanid in Wasser zu einheitlichen Produkten. 3a liefert mit Ammoniak Methyl-4-amino-4,6-didesoxy-βD-xylo-hex-5-enopyranosid (4a); 3b ergibt das α-Anomere 4b. Durch Acetylierung von 4b und nachfolgende katalytische Hydrierung erhält man Methyl-4-acetamido-2,3-di-O-acetyl-4,6-didesoxy-α-D-glucopyranosid (5b), dessen Eigenschaften mit denen eines bekannten 2) Derivats des in den Antibiotica Amicetin und Bamicetin enthaltenen Viosamins (4,6-Didesoxy-4-amino-α-Dglucose) übereinstimmen. 3a und 3b reagieren mit Natriumazid in wenigen Minuten wahrscheinlich zunächst zu Methyl-4-azido-4,6-didesoxy-β-D-xylo-hex-5-enopyranosid und -α-D-xylo-hex-5-enopyranosid (6a bzw. 6b). Die Verbindungen 6a und 6b sind instabil und lagern sich im Verlauf von einigen Stunden in Methyl-6-azido-4,6-didesoxy-α-L-threo-hex-4-enopyranosid und -β-L-threo-hex-4-enopyranosid (7a bzw. 7b) um. Die Umsetzung von 3a mit Natriumcyanid ergibt Methyl-4-cyan-4,6-didesoxy-α-L-threo-hex-4-enopyranosid (9), das offensichtlich durch Tautomerisierung aus dem primär gebildeten, aber nicht nachweisbaren Methyl-4-cyan-4,6-didesoxy-β--D-xylo-hex-5-enopyranosid (8) entsteht. Die Gruppierung eines Vinyloxirans macht Verbindungen vom Typ 3a und 3b, wie die Beispiele zeigen, zu wertvollen Ausgangsprodukten für regio- und stereoselektive Synthesen spezieller Monosacharidderivate. Reactions of Enolic Sugar Derivatives, XI. — Reaction of Methyl 3,4-Anhydro-6-deoxy-α-L-arabino-hex-5-enopyranoside and -β-L-arabino-hex-5-enopyranoside with Nucleophiles At room temperature methyl 3,4-anhydro-6-deoxy-α-L-arabino-hex-5-enopyranoside1) (3a) as well as its β-anomer 3b react smoothly with methanolic ammonia, aqueous sodium azide and aqueous sodium cyanide to give uniform products. Reaction of 3a and of 3b with ammonia affords methyl 4-amino-4,6-dideoxy-β-D-xylo-hex-5-enopyranoside (4a) and the corresponding α-anomer 4b, respectively. Acetylation of 4b and subsequent catalytic hydrogenation leads to methyl 4-acetamido-2,3-di-O-acetyl-4,6-dideoxy-α-D-glucopyranoside (5b). The properties of 5b are consistent with those of a viosamine derivative2). 3a and 3b react with sodium azide within few minutes probably at first to methyl 4-azido-4,6-dideox-β-D-xylo-hex-5-enopyranoside and -α-D-xylo-hex-5-enopyranoside (6a and 6b) The compounds 6a and 6b are unstable and rearrange during the course of several hours to methyl 6-azido-4,6-dideoxy-α-L-threo-hex-4-enopyranoside and -βL-threo-hex-4-enopyranoside (7a and 7b). Reaction of 3a with sodium cyanide yields methyl 4-cyano-4,6-dideoxy-α-L-threo-hex-4-enopyranoside (9). The pyranoside 9 is most probably formed by tautomerization of the unidentified primary product methyl 4-cyano-4,6-dideoxy-β-D-xylo-hex-5-enopyranoside (8). As shown by several examples, compounds like 3a and 3b containing a vinyl epoxide grouping are useful starting materials for regio- and stereoselective syntheses of rare monosaccharides." @default.
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- W2019298510 title "Reaktionen enolischer Zuckerderivate, XI. Umsetzung von Methyl-3,4-anhydro-6-desoxy-α-L-arabino-hex-5-enopyranosid und -β-L-arabino-hex-5-enopyranosid mit Nucleophilen" @default.
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