Reactions of nitro sugars. V. Some reactions with methyl 3-deoxy-3-nitro-α-d-hexopyranosides

Abstract

The acetylations and catalytic hydrogenations of derivatives of methyl 3-deoxy-3-nitro-α-d-hexopyranosides were compared with the analogous reactions previously performed in the β-anomeric series. The acetylation of methyl 4,6-O-benzylidene-3-deoxy-3-nitro-α-d-glucopyranoside (II) gave its 2-O-acetyl derivative III, which, upon base-catalyzed elimination of acetic acid, yielded the nitroolefin, methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-α-d-erythro-hexopyranos-2-enide (IV), whereas acetylation of the corresponding α-d-talopyranoside XI proceeded with dehydration, giving directly the α-d-threo nitroolefin XIII. These courses of reaction had their counterparts in the β-series and are believed to depend on the configurations at C-4. On the other hand, palladium-catalyzed hydrogenations of the nitroolefins IV and XIII gave results that were similar to each other but different from those obtained in the β-series. Besides the expected saturated nitro glycosides with α-d-arabino (V) and α-d-lyxo (XV) configurations, two oximes (VI and XIV) were produced in yields of 49 and 30%, respectively. This may be attributed to a measure of steric interference by the glycosidic methoxyl group during the hydrogenation of the olefinic double bonds in IV and XIII. Amino glycosides were obtained from V and XV by debenzylidenation and platinum-catalyzed hydrogenation.