Photoinduced addition of glycosyl thiols to alkynyl peptides: use of free-radical thiol-yne coupling for post-translational double-glycosylation of peptides.

Double glycosylation of cysteine-containing peptides has been carried out by a one-pot two-step sequence comprising selective S-propargylation followed by photoinduced (lambda (max) 365 nm) free-radical hydrothiolation with glycosyl thiols. Conditions were established for the sequential introduction of two different thiol residues such as a glycosyl and a biotinyl derivative.