Synthesis of a precursor of β-d-glcpnac(l-→2)-α-d-manp-(l-→-3)-[β-d-xylp-(1 →2)]-β-d-manp-(1→4) - β-d-glcp1

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 4-0-methyl-D-glucopyranosyl uronic acid groups. The pentasaccharide derivatives that constitute the partial structure of lipid IV were synthesized as follows. 4, 6-Di-0.-acetyl-2-0-(2, 3, 4 -tri-0-acetyl-β-D-xylopyran-osyl)-3-0benzyl-a-D-mannopyranosyl bromide was treated with 2, 3-di-0-acetyl-1, 6-anhydro-p-D-glucopyranose in the presence of silver zeolite to afford the corresponding trisaccharide. The formation of the p-glycoside took precedence as a major product in a ratio of 6.9:1. After debenzylation, the p-mannosyl trisaccharide derivative was condensed with 3, 4, 6-tri-0-acetyl-2-0.-chloroacetyl- a -D-mannopyranosyl bromide in the presence of silver triflate, and the final pentasaccharide derivative was prepared by using a suitably protected tetrasaccharide as the glycosyl acceptor, 3-0-acetyl-6-07benzyl-4-()-chloroacetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide as the donor and silver triflate as the promoter, respectively.