Preparation of building blocks for glycopeptide synthesis by glycosylation of Fmoc amino acids having unprotected carboxyl groups

Abstract

N α -Fmoc amino acids with an unprotected α-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 α -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.