Chiral acidic amino acids as tethers for intramolecular glycosylation

Intramolecular glycosylation with peptides as tethers is attractive for the synthesis of oligosaccharides because conjugation between the amino acids present in the tethers is facile. However, few studies have been published about the effects of the amino acid side chain length and amino acid chirality on the glycosylation process. In this study, we revealed that the chain length of the amino acid can regulate the regioselectivity of the glycosylation process based on our observation that the 1,2-linked products were preferred when tethers were those having aspartic acid residues linked to each other, while 1,3-linked products were preferred for glutamic acid-based tethers. However, the amino acid chirality was found to have no effect on the yield and stereoselectivity of the glycosylation reaction.