Chemoselective coupling of sugar oximes and α-ketoacids to glycosyl amides and N-glycopeptides

The reaction of unprotected sugar hydroxylamines and oximes with α-ketoacids leads to the chemoselective formation of glycosyl amides following the decarboxylative condensation pathway of Bode’s ketoacid hydroxylamine (KAHA) ligation. Sugar oximes with gluco configuration stereoselectively form β-linked products. This method can be used for the convergent synthesis of N-acylated sugars and oligosaccharides bearing small labels, spacers, or peptides in the acyl part.