Preparation of S- and N-linked glycosylated amino acid building blocks for solid-phase glycopeptide library synthesis

A general route for the preparation of 1,2-trans-linked S-glycosylated amino acid building blocks by a Lewis-acid-promoted condensation of peracetylated glycosyl donors and N-alpha-Fmoc-Cys-OH, in good overall yield, is described. In addition, a short and time-efficient route was applied for the synthesis of N-glycosylated amino acid building blocks in good overall yields by coupling unprotected glycosylamines and N-alpha-Fmoc-Asp(OH)-(OBu)-Bu-t using TBTU activation.