Synthesis of a tri- and a hepta-saccharide which contain alpha-L-fucopyranosyl groups and are part of the complex type of carbohydrate moiety of glycoproteins.

Reaction of a thioglycoside with methyl trifluoromethanesulfonate (methyl triflate) in the presence of a hydroxyl compound is an efficient glycosylation method. Thus, methyl triflate-promoted condensation of ethyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-1-thio-3-O-(2,3,4-tri-O-benzyl-a lpha-L- fucopyranosyl)-beta-D-glucopyranoside with benzyl 3,4,6-tri-O-benzyl-alpha-D-mannopyranoside and with benzyl 2,4-di-O-benzyl-3,6-di-O-(3,4,6-tri-O-benzyl-alpha-D-mannopyranosyl)-alp ha-D- mannopyranoside gave a trisaccharide and a heptasaccharide derivative, respectively. The trisaccharide 1 and the heptasaccharide 2, which are parts of the complex type of glycoproteins, were obtained by removal of the protecting groups and N-acetylation. (formula: see text).