Synthesis of new glycosyl-α-aminoacid derivatives for glycopeptide chemistry

The synthesis of new N- or C-protected glycosyl-α-aminoacids and their use to prepare new glycopeptides is described. The overall synthetic strategy to obtain these new α-aminoacid chirons involves four distinct steps from dialdoses: (1) a diastereoselective Darzens reaction between the potassium anion derived from isopropyl dichloroacetate and a suitable protected dialdose, (2) the one-pot transformation of the so-obtained isopropyl glycosyl-α-chloroglycidic ester with magnesium iodide, then sodium hydrogenosulfite, into an isopropyl glycosyl-α-ketoester, (3) the reductive amination of the α-ketoester with (S)-α-methylbenzylamine and an hydrogenating reagent, (4) N- or C-selective deprotection and further peptidic coupling.