Synthesis of 2-acetamido-2-deoxy-3-O-beta-D-mannopyranosyl-D-glucose

Condensation of 4,6-di-O-acetyl-2,3-O-carbonyl-alpha-D-mannopyranosyl bromide with benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside (2) gave an alpha-D-linked disaccharide, further transformed by removal of the carbonyl and benzylidene groups and acetylation into the previously reported benzyl 2-acetamido-4,6-O-benzylidene groups and acetylation into the previously reported benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-alpha-D-glucopyranoside. Condensation of 3,4,6-tri-O-benzyl-1,2,-O-(l-ethoxyethylidene)-alpha-D-glucopyranose or 2-O-acetyl-3,4,6-tri-O-benzyl-alpha-D-glucopyranosyl bromide with 2 gave benzyl 2-acetamido-3-O-(2 O-acetyl-3,4,6-tri-O-benzyl-beta-D-glucopyranosyl)-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside. Removal of the acetyl group at O-2, followed by oxidation with acetic anhydride-dimethyl sulfoxide, gave the beta-D-arabino-hexosid-2-ulose 14. Reduction with sodium borohydride, and removal of the protective groups, gave 2-acetamido-2-deoxy-3-O-beta-D-mannopyranosyl-D-glucose, which was characterized as the heptaacetate. The anomeric configuration of the glycosidic linkage was ascertained by comparison with the alpha-D-linked analog.