Synthetic mucin fragments: Benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-3-O-β-d-galactopyranosyl-α-d-galactopyranoside and benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-3-O-[6-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-β- d-galactopyranosyl]-2-deoxy-α-d-galactopyranoside

Glycosylation of benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-galactopyranoside with 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide, catalyzed by mercuric cyanide, afforded benzyl-2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-galactopyranoside (3). O-Deacetylation of 3 gave benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-β-d-galactopyranosyl-α-d-galactopyranoside which, on acetalation with benzaldehyde-zinc chloride complex followed by acetylation of the resulting dibenzylidene acetal, gave the disaccharide diacetate (7). Cleavage of the acetal groups of 3 and 7 in hot, 80% aqueous acetic acid furnished, respectively, the disaccharide tetraacetate (4) and diacetate (8). O-Deacetylation of 8 in methanolic sodium methoxide gave the disaccharide (9). Condensation of 4 or 8 with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)-[2,1-d]-2-oxazoline, followed by O-deacetylation, afforded the title tri- and tetra-saccharides, 12 and 14, respectively. The structures of compounds 9, 12, and 14 were established by ¹³C-n.m.r. spectroscopy.