Chemoenzymatic synthesis of the 3-sulfated Lewisa pentasaccharide

The sulfated pentasaccharide benzyl O-(3-O-sulfo-beta-D-galactopyranosyl)-(1-->3)-O-(alpha-L-fucopyranosyl)-(1-->4)]-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-(1-->3)-O-(beta-D-galactopyranosyl)-(1-->4)-O-beta-D-glucopyranoside sodium salt was synthesized using a chemo-enzymatic approach. Lacto-N-tetraose, obtained from two disaccharides 4-methoxybenzyl O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1-->3)-4,6-O-benzylidene-2-deoxy-2-phtalimido-beta-D-glucopyranoside and benzyl 2,6-di-O-acetyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-acetyl-beta-D-glucopyranoside], was regioselectively sulfated at the 3 OH position of the terminal galactose using the stannylene procedure. The fucosylation of the sulfated tetrasaccharide was performed using soluble or immobilized fucosyltransferase FucT-III to give the title compound.