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-α- l-fucopyranosyl)-β- d-glucopyranoside with benzyl 3,4,6-tri- O-benzyl-α- d-mannopyranoside and with benzyl 2,4-di- O-benzyl-3,6-di- O-(3,4,6-tri- O-benzyl-α- d-mannopyranosyl)-α- 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. ▪