An Economical Synthesis of Lewis X, Sialyl Lewis X and Their α-Galactosyl Analogues

Abstract

Economical syntheses of the Lewis X trisaccharide 8 and sialyl Lewis X tetrasaccharide 18 epitopes and the syntheses of the α-galactosyl epimers 9 and 20 of these structures are described. Thioglycosides 2, 5, 11 and 15 were used as glycosyl donors to construct the desired compounds in a stepwise manner in dimethyl(methylthio)sulphonium triflate promoted couplings. Benzyl 3-O-(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-2-acetamido-6-O-benzyl-2-deoxy-α-D-glucopyranoside (4) was a key structure in these syntheses, and was synthesised in multi-gram scale.