TOTAL SYNTHESIS OF THE MOLLU-SERIES GLYCOSYL CERAMIDES - ALPHA-D-MANP-(1-]3)-BETA-D-MANP-(1-]4)-BETA-D-GLCP-(1-]1)-CER AND ALPHA-D-MANP-(1-]3)-[BETA-D-XYLP-(1-]2)]-BETA-D-MANP-(1-]4)-BETA-D-GLCP-(1-]1)-CER

The mollu-series glycosphingolipids, O-α-d-mannopyranosyl-(1→3)-O-β-d-mannopyranosyl-(1→4)-O-β-d-glucopyranosyl - (1→1)-2-N-tetracosanoyl-(4E)-sphingenine and O-α-d-mannopyranosyl-(1→3)-O-[β-d-xylopyranosyl-(1→2)]-O-β-d-mannopyranosyl-(1→4) -O-β-d-glucopyranosyl-(1→1)-2-N-tetracosanoyl-(4E)-sphingenine, were synthesized for the first time by using 2,3,4-tri-O-acetyl-d-xylopyranosyl trichloroacetimidate, methyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-mannopyranoside, benzyl O-(4,6-di-O-benzyl-β-d-mannopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-d-glucopyranoside 9, and (2S,3R,4E)-2-azido-3-O-(tert-butyldiphenylsilyl)-4-octadecene-1,3-diol 6 as the key intermediates. The hexa-O-benzyl disaccharide 9 was prepared by coupling two monosaccharide synthons, namely, 2,3-di-O-allyl-4,6-di-O-benzyl-α-d-mannopyranosyl bromide and benzyl 2,3,6-tri-O-benzyl-β-d-glucopyranoside. It was demonstrated that azide 6 was highly efficient as a synthon for the ceramide part in the coupling with both glycotriaosyl and glycotetraosyl donors, particularly in the presence of trimethylsilyl triflate. © 1990.