Glycoconjugate and oligosaccharide mimetics by chemoselective ligation

Different approaches for the synthesis of neoglycoconjugates, exploiting chemoselective ligation procedures, are reported. Based on the reaction of the carbonyl group of ketones or aldehydes (including the anomeric centre of the sugar) with strong nucleophiles such as hydroxylamino- or hydrazino-derivatives, or on the addition of sulfidryl groups to a variety of electrophiles, these procedures afford bioactive neo-glycoconjugates avoiding protection–deprotection and activation steps. Conjugation of two copies of the C-saccharide analogue of the T n epitope with the immunogenic peptide OVA (327–339) by way of chemoselective ligation, afforded a neo-glycopeptide capable of inducing in vivo B- and T-cell response to tumours exposing T n epitope.