Branched-chain sugars. Part 16. The synthesis of a derivative of 3-amino-2,3,6-trideoxy-3-C-methyl-L-xylo-hexopyranose, the novel branched-chain amino sugar of antibiotic A35512B

Methyl 2,6-dideoxy-4-O-methoxymethyl-α-L-erythro-hexopyranosid-3-ulose (1) reacted with potassium cyanide under equilibrating conditions to give methyl 3-C-cyano-2,6-dideoxy-4-O-methoxymethyl-α-L-arabino-hexopyranoside (11). The mesylate (12) derived from this cyanohydrin was converted by established procedures, although not without difficulty, into methyl 3-acetamido-2,3,6-trideoxy-4-O-methoxymethyl-3-C-methyl-α-L-ribo-hexopyranoside (17), which was then converted in a straightforward manner into methyl 3-acetamido-2,3,6-trideoxy-3-C-methyl-α-L-ribo-hexopyranoside (20). Inversion of the configuration at C-4 of the latter compound, by means of an oxidation–reduction sequence, yielded methyl 3-acetamido-2,3,6-trideoxy-3-C-methyl-α-L-xylo-hexopyranoside (22), a derivative of the novel branched-chain amino sugar found in antibiotic A35512B.