Synthetic studies on an oligosaccharide of a glycolipid from the spermatozoa of bivalves IX. Syntheses of lipids I, II, and IV

Abstract

Glycosphingolipids isolated from the spermatozoa of the freshwater bivalve, Hyriopsis schlegelii, have a unique structure containing one or two mannosyl residues and novel linkages, including an internal fucopyranosyl residue, as well as terminal xylosyl and 4- O-methyl- d-glucopyranosyluronic acid groups. The octasaccharide of lipid IV was synthesized as follows. Condensation of methyl (2-acetamido-4,6-di- O-acetyl-2-deoxy-3- O-methyl- α- d-galactopyranosyl)-(1 → 3)-[methyl(2,3-di- O-acetyl-4- O-methyl-β- d-glucopyranosyluronate)- (1 → 4)]-2- O-benzyl-1-thio-α,β- l-fucopyranoside ( 18) with (3- O-acetyl-6- O-benzyl-2-deoxy- 2-phthalimido-β- d-glucopyranosyl)-(1 → 2)-(3,4,6-tri- O-acetyl-α- d-mannopyranosyl)-(1 → 3)-[(2,3,4-tri- O-acetyl-β- d-xylopyranosyl)-(1 → 2)]-(4,6-di- O-acetyl-β- d-mannopyranosyl)-(1 → 4)-2,3-di- O-acetyl-1,6-anhydro-β- d-glucopyranose ( 14), in the presence of dimethyl (methylthio) sulfonium triflate (DMTST), gave the corresponding octasaccharide ( 19). Removal of the protecting groups gave 2-acetamido-2-deoxy-3- O-methyl-α- d-galactopyranosyl-(1 → 3)-[4- O-methyl-β- d-glucopyranosyl uronic acid-(1 → 4)]-α- l-fucopyranosyl- (1 → 4)-2-acetamido-2-deoxy-β- d-glucopyranosyl-(1 → 2)-α- d-mannopyranosyl-(1 → 3)-[β- d- xylopyranosyl-(1 → 2)]-β- d-mannopyranosyl-(1 → 4)-1,6-anhydro-β- d-glucopyranose ( 22). The other two oligosaccharides that constitute the partial structure of lipid IV, called lipid I and II, were also synthesized.