Synthesis of a precursor of 3- O-(2-acetamido-2-deoxy-3- O-methyl-α- d-galactopyranosyl)-4- O-(4- O-methyl-β- d-glucopyranosyluronic acid)- l-fucose

Abstract

The glycosphingolipids isolated from spermatozoa of a fresh-water bivalve, Hyriopsis schlegelii, have a unique structure containing one or two mannosyl residues, novel linkages including an internal fucopyranosyl residue, as well as terminal xylosyl and 4- O-methyl- d-glucopyranosyluronic acid groups. The trisaccharide derivatives that constitute the partial structure of lipid IV were synthesized as follows. Condensation of 4,6-di- O-acetyl-2-azido-2-deoxy-3- O-methyl-α- d-galactopyranosyl bromide with 2-(trimethylsilyl)ethyl 4- O-acetyl-2- O-benzyl-β- l-fucopyranoside, in the presence of mercuric cyanide and mercuric bromide, gave the corresponding disaccharide in 87% yield. Condensation of methyl (2,3-di- O-acetyl-4- O-methyl-α- d-glucopyranosyl bromide)uronate with the appropriate OH-4-free disaccharide derivative afforded the corresponding precursor of 4- O-Me-β- d-Glc pA-(1→4)-[3- O-Me-α- d-Gal pNAc-(1→3)]- l-Fuc, namely 2-(trimethylsilyl)ethyl 2- O-benzyl-3- O-(4,6-di- O-acetyl-2-azido-2-deoxy-3- O-methyl-α- d-galactopyranosyl]-4- O-[methyl (2,3-di- O-acetyl-4- O-methyl-β- d-glucopyranosyl)uronate]-β- l-fucopyranoside.