Synthesis of O-β-D-galactopyranosyl-(1→4)-O-2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→3)-D-mannose, a postulated trisaccharide of human erythrocyte membrane sialoglycoprotein

Abstract

Monoallylation of tributylstannylated benzyl 6-O-trityl-α-D-mannopyranoside (3) was efficiently catalysed by tetrabutylammonium bromide to give the 3-O-(4) and 2-O-(5) allyl ethers in 62 and 15% yields, respectively. Compound (4) was converted into crystalline benzyl 3-O-allyl-2,4-di-O-benzyl-α-D-mannopyranoside (10), which was then isomerized, allylated, and hydrolysed to give benzyl 6-O-allyl-2,4-di-O-benzyl-α-D-mannopyranoside (11). This compound was condensed with the oxazoline (12), derived from D-lactosamine, to give the protected trisaccharide (13) in 9% yield. Removal of the protecting groups gave the free trisaccharide β-D-Gal-(1→4)-β-D-GlcNAc-(1→3)-D-Man (15). The carbohydrate sequence of this trisaccharide has been postulated in some membrane glycoproteins and will be tested for its li blood group activity.