A Convenient and Efficient Synthesis of Sialyl Lewis X

A convenient synthesis of the sialyl Lewis X (sLex) tetrasaccharide, NeuAcα2-3Galβ1-4(Fucα1-3)GlcNAc (8), as a carbohydrate ligand for selectins is described. The key step is the reaction between NeuAcα2-3GalSMe (5) as a glycosyl donor and the suitably protected Fucα1-3GlcNAc derivative (4) as the glycosyl acceptor by using dimethyl(methylthio)sulfonium triflate (DMTST) as the promoter.