title: Synthesis of methyl 3-O- and 2-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-alpha D-galactopyranoside.
abstract: Condensation of methyl 2-O-benzoyl-4,6-O-benzylidene-alpha-D-galactopyranoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl bromide (1) in dichloromethane, in the presence of silver trifluoromethanesulfonate, 2,4,6-trimethylpyridine, and molecular sieves, afforded methyl 2-O-benzoyl-4,6-O-benzylidene-3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalim ido- beta-D-glucopyranosyl)-alpha-D-galactopyranoside (4). Deacetalation of 4 in hot, 80% aqueous acetic acid gave methyl 2-O-benzoyl-3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido- beta-D-glucopyranosyl)-alpha-D-galactopyranoside (5), which, on deacylation, followed by peracetylation, furnished the peracetylated disaccharide derivative (6). The structures of 5 and 6 were established by 1H-n.m.r. spectroscopy. O-Deacetylation of 6 afforded the title beta-(1 leads to 3)-linked disaccharide 7. For the synthesis of the beta-(1 leads to 2)-linked isomer, methyl 3-O-benzoyl-4,6-O-benzylidene-alpha-D-galactopyranoside was similarly condensed with bromide 1 to give the fully protected disaccharide derivative (8). Cleavage of the benzylidene group of 8 gave methyl 3-O-benzoyl-2-O-(3,4,6- tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-alpha-D- galactopyranoside (9). Deacetylation of 9, followed by peracetylation, afforded the peracetate (10). O-Deacetylation of 10 gave the beta-(1 leads to 2)-linked disaccharide (11). The structures of the disaccharides 7 and 11 were confirmed by 13C-n.m.r. spectroscopy.
mesh_terms: D001789:Blood Group Antigens; D002236:Carbohydrate Conformation; D004187:Disaccharides / Q000138:chemical synthesis*; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008895:Milk, Human / Q000032:analysis; D009844:Oligosaccharides; D011247:Pregnancy
chemical_list: D001789:Blood Group Antigens; D004187:Disaccharides; D007202:Indicators and Reagents; D009844:Oligosaccharides; C040457:lacto-N-biose II (1-2 isomer); C040456:lacto-N-biose II