Synthesis of aliphatic O-dimannosyl amino acid building blocks for solid-phase assembly of glycopeptide libraries

The preparation of α(1,2)-, α(1,3)- and α(1,6)-linked mannose disaccharides is described. The protected α-D-Man(1→3)-D-Man disaccharide was synthesized using the trichloroacetimidate method, while the Königs–Knorr procedure was employed in the preparation of the 1→2- and 1→6-linked disaccharides. Glycosylation of Nα-Fmoc-Ser-OPfp, Nα-Fmoc-Thr-OPfp and Nα-Fmoc-Hyp-OPfp with the dimannosyl bromides afforded the activated building blocks, in moderate to high yield, for direct use in solid-phase synthesis of glycopeptide libraries.