Solid-phase synthesis of an O-linked glycopeptide based on a benzyl-protected glycan approach

The solid-phase synthesis of asialo-[Ala18]-B-chain (2) of human α2HS glycoprotein is described. Disaccharide-linked serine unit 12, carrying a benzyl protecting group, was synthesized via stereoselective glycosylation of 8 with 6. Peptide synthesis was carried out by the Fmoc method utilizing an automated peptide synthesizer. A modified procedure using a mechanical shaker at the coupling step with 12 made easy the recovery of unreacted 12. The benzylated glycopeptide thus synthesized was cleaved from the resin and hydrogenated to give 2.