Synthetic mucin fragments. Benzyl O-β-d-galactopyranosyl-(1→3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→6)-2-acetamido-2-deoxy-α-d-galactopyranoside and O-α-l-fucopyranosyl-(1→3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→6)-2-acetamido-2-deoxy-d-galactopyranose

Benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-4,6-O-isopropylidene-β-d-glucopyranosyl)-2-deoxy-3,4-O-isopropylidene-α-d- galactopyranoside (2) was obtained by acetalation of its parent disaccharide with 2,2-dimethoxypropane in hot N,N-dimethylformamide and in the presence of 4-toluenesulfonic acid. Glycosylation of 2 with 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide (catalyzed by mercuric cyanide), followed by removal of the protecting groups afforded the title trisaccharide 7. A second product was also isolated, which was identified as a derivative of 7 having a 2-cyanopropyl group. Glycosylation of diacetal 2 with 2,3,4-tri-O-benzyl-α-l-fucopyranosyl bromide (under catalysis by bromide ion), followed by systematic removal of the protecting groups furnished the title trisaccharide 13. The structures of both 7 and 13 were established by ¹³C-n.m.r. spectroscopy.