Synthesis of benzyl O-(2-O-methyl-β-d-galactopyranosyl)-(1→3)-2-acetamido-2-deoxy-β-d-glucopyranoside [benzyl 2′-O-methyllacto-N-bioside I], and its higher saccharide containing an O-(2-O-methyl-β-d-galactopyranosyl)-(1→3)-2-acetamido-2-deoxy-β-d-glucopyranosyl group as a potential substrate for (1→4)-α-l-fucosyltransferase

Treatment of benzyl O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-4,6-O-isopropylidene-β-d-glucopyranoside with tert-butychlorodiphenylsilane afforded the 6′-O-tert-butyldiphenylsilyl ether, which was converted into the 3′,4′-O-isopropylidene derivative. Methylation and subsequent removal of protecting groups afforded benzyl O-(2-O-methyl-β-d-galactopyranosyl)-(1→3)-2-acetamido-2-deoxy-β-d-glucopyranoside (7). The trisaccharide methyl O-(2-O-methyl-β-d-galactopyranosyl)-(1→3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)- (1→3)-β-d-galactopyranoside (17) and the tetrasaccharide O-(2-O-methyl-β-d-galactopyranosyl)-(1→3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→3)-O-β-d- galactopyranosyl-(1→4)-d-glucopyranose (32), both containing the 2′-O-methyllacto-N-biose I unit at the non-reducing end, were synthesized, and the structures of 7, 17, and 32 were confirmed by ¹³C-n.m.r. spectroscopy.