Synthesis of a novel N–O-interglycosidic disaccharide

The carbohydrate subunits carrying an N–O-interglycosidic bond play a very important role in the biological activity of the enediyne antibiotics. Condensation of O-(α- and β-d-glucopyranosyl)hydroxylamine (5a and 5b) with the hex-3-ulopyranoside (6) furnished methyl 4,6-O-benzylidene-2,3-dideoxy-3-(2,3,4,6-tetra-O-benzyl-α-d-glucopyranosyloxy)imino-α- and β-d-erythro-hexopyranoside (7a and 7b). Stereoselective reduction of the CN bond of 7a and 7b with sodium cyanoborohydride resulted in the formation of the required protected N–O-interglycosidic disaccharides (8a and 8b). Finally, catalytic hydrogenation of 8a afforded methyl 2,3-dideoxy-3-(α-d-glucopyranosyloxy)amino-α-d-ribo-hexopyranoside (9a). Under similar conditions the β anomer 8b underwent decomposition.