Chemoselective Glycosylation of Peptides through S-Alkylation Reaction.

An efficient and rapid procedure for synthesizing S-linked glycopeptides is reported. The approach uses activated molecular sieves as a base to promote the selective S-alkylation of readily prepared cysteine-containing peptides, upon reaction of appropriate glycosyl halides. Considering the very mild conditions employed, the chemoselective linkage of the electrophilic sugar with a peptide sulfhydryl group occurred in satisfactory yield, allowing the incorporation of mono and disaccharide moieties. The sugar-peptide conjugates obtained from α-d-glycosyl derivatives adopt a β-S-configuration, indicating the high stereoselectivity of the substitution reaction.