PREPARATION OF BUILDING-BLOCKS FOR GLYCOPEPTIDE SYNTHESIS BY GLYCOSYLATION OF FMOC AMINO-ACIDS HAVING UNPROTECTED CARBOXYL GROUPS

N-alpha-Fmoc amino acids with an unprotected alpha-carboxyl group have been glycosylated with carbohydrate 1,2-trans peracetates using Lewis acids as promoters. Aliphatic and phenolic O- and S-glycosides of amino acids, with a 1,2-trans anomeric configuration, were obtained as products in 34-65% yields. The glycosylated building blocks have the protective groups of choice (i.e. O-acetyl and N-alpha-Fmoc) for direct use in stepwise synthesis of glycopeptides. The starting materials are readily available and the method does not require an extensive experience in synthetic carbohydrate chemistry.