Synthetic mucin fragments. Benzyl O-(2-acetamido-2-deoxy-α-d-glucopyranosyl)-(1→3)-O-β-d-g alactopyranosyl-(1→3)-O-...

Title full: Synthetic mucin fragments. Benzyl O-(2-acetamido-2-deoxy-α-d-glucopyranosyl)-(1→3)-O-β-d-g alactopyranosyl-(1→3)-O- [(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→6)]-2-acetamido-2 -deoxy-α-d-galactopyranoside and benzyl O-(2-acetamido-2-deoxy- β-d-glucopyranosyl)-(1→3)-O-β-d-galactopyranosyl-(1→ 3)-O-[β-d-galactopyranosyl-(1→6)]-2-acetamido-2-deoxy-α- d- galactopyranoside. Treatment of benzyl 2-acetamido-2-deoxy-α-d-galactopyranoside with 4-methoxybenzaldehyde dimethyl acetal in N,N-dimethylformamide in the presence of 4-toluenesulfonic acid afforded the 4,6-O-(4-methoxybenzylidene) acetal, which was glycosylated with 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide (1). Reductive ring-opening of the acetal group provided a 6-O-(4-methoxybenzyl) derivative (4) which was glycosylated with 1, followed by removal of the 4-methoxybenzyl ether group, to give benzyl 2-acetamido-2-deoxy-3,4-di-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyr anosyl)-α-d-galactopyranoside (7). The disaccharide diol 5, obtained from 4, and benzyl O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl- (1→3)-O-(2,4,6-tri-O- acetyl-β-d-galactopyranosyl)-(1→3)-2-acetamido-2-deoxy-α -d-galactopyranoside (11) were similarly glycosylated with 1 to afford a trisaccharide derivative 9 and a tetrasaccharide derivative 14, respectively. Diol 11 was also condensed with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)-[2,1-d]- 2-oxazoline to give a tetrasaccharide derivative 16. O-Deacetylation of trisaccharides 7 and 9, and tetrasaccharides 14 and 16 furnished trisaccharides 8 and 10, and the title tetrasaccharides 15 and 17, respectively. The structures of compounds 8, 10, 15, and 17 were established by ¹³C-n.m.r. spectroscopy.