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

The synthesis of new N- or C-protected glycosyl-alpha -aminoacids and their use to prepare new glycopeptides is described. The overall synthetic strat egy to obtain these new alpha -aminoacid chirons involves four distinct ste ps from dialdoses: (1) a diastereoselective Darzens reaction between the po tassium anion derived from isopropyl dichloroacetate and a suitable protect ed dialdose, (2) the one-pot transformation of the so-obtained isopropyl gl ycosyl-alpha -chloroglycidic ester with magnesium iodide, then sodium hydro genosulfite, into an isopropyl glycosyl-alpha -ketoester, (3) the reductive amination of the alpha -ketoester with (S)-alpha -methylbenzylamine and an hydrogenating reagent, (4) N- or C-selective deprotection and further pept idic coupling. (C) 2001 Elsevier Science Ltd. All rights reserved.