Syntheses of model oligosaccharides of biological significance. 4. Synthesis of a fucosylated N,N′-diacetylchitobioside and related oligosaccharides

Abstract

The synthesis of two trisaccharides and one disaccharide containing L-fucose and 2-acetamido-2-deoxy-D-glucose is reported. Methyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranoside was glycosylated with a 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide. Removal of the phthalimido protecting groups by hydrazinolysis followed by N-acetylation and debenzylation yielded methyl N,N′-diacetylchitobioside 3′,4′,6′-triacetate. The latter was selectively fucosylated at the 6-position with 2,3,4-tri-O-benzyl-α-L-fucopyranosyl bromide to yield, after debenzylation and de-O-acetylation, methyl 2-acetamido-4-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-deoxy-6-O-(α-L-fucopyranosyl)-β-D-glucopyranoside. When methyl 3-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranoside was fucosylated, its 6-O-and 4,6-di-O-(α-L-fucopyranosyl) derivatives were obtained by use of 1 and 2 equivalents, respectively, of the protected fucosyl bromide.