Oligosaccharide–Peptide Ligation of Glycosyl Thiolates with Dehydropeptides: Synthesis of S‐Linked Mucin‐Related Glycopeptide Conjugates

Abstract A chemoselective strategy for oligosaccharide–peptide ligation is described in which α‐thio analogues of mucin‐related glycoconjugates can be readily accessed through site‐selective conjugate addition of complex oligosaccharide thiolates to dehydroalanine‐containing peptides. The efficiency of the ligation is highlighted by the rapid convergent assembly of thio‐isosteres of the four tumor‐associated carbohydrate antigens, T N , T, ST N , and 2,6‐ST, as a pair of diastereoisomers at the newly formed cysteine stereocenter. The process proceeds in high yield and with complete retention of the α‐anomeric configuration.