Sigmatropic rearrangements as tools for amino acid and peptide modification: application of the allylic sulfur ylide rearrangement to the preparation of neoglycoconjugates and other conjugates.

Reaction of S-allyl cysteine derivatives, generated by the selenocysteine ligation, with rhodium carbenoids, stabilized and unstabilized, enables the attachment of diverse functionality onto cysteine residues. The reaction is successfully applied to the introduction of lipid-like residues, a fluorous alkyl chain, and mono- and disaccharides.