Chemoenzymatic synthesis of the 3-sulfated Lewisa pentasaccharide

The sulfated pentasaccharide benzyl O-(3-O-sulfo-β-d-galactopyranosyl)-(1→3)-O-[(α-l-fucopyranosyl)-(1→4)]-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→3)-O-(β-d-galactopyranosyl)-(1→4)-O-β-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-β-d-galactopyranosyl)-(1→3)-4,6-O-benzylidene-2-deoxy-2-phtalimido-β-d-glucopyranoside and benzyl 2,6-di-O-acetyl-β-d-galactopyranosyl-(1→4)-2,3,6-tri-O-acetyl-β-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.