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

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.