Preparation of a glycosyl donor suitable for synthesis of glycoprotein “core” oligosaccharides

Abstract 2- O -Acetyl-3- O -allyl-4- O -benzyl-6- O-tert -butyldiphenylsilyl- d -glucopyranosyl chloride ( 14 ), a glycosyl donor suitable for synthesis of oligosaccharides corresponding to the N-glycoprotein saccharide “core”, was synthesized by an efficient, six-stage route from 3,4,6-tri- O -acetyl-1,2- O -[1-( exo -ethoxy)ethylidene]-α- d -glucopyranose. Silver triflate-promoted coupling of 14 with benzyl 2-acetamido-3,6-di- O -benzyl-2-deoxy-α- d -glucopyranoside gave a protected β- d -(1→4)-linked disaccharide in 38% yield, but a major side-reaction also occurred. When the tert -butyldiphenylsilyl group was quantitatively removed from 14 prior to the coupling reaction, and replaced afterwards, the yield in the glycosidation was increased to 55%, and major side-products were avoided.