Synthesis of glycosyltyrosine building blocks for solid-phase glycopeptide assembly: use of aryl tert-butyl ethers as glycosyl acceptors in aromatic glycosylations

Abstract

The synthesis of the suitably protected building blocks for solid-phase glycopeptide synthesis, N^α-Fmoc-Tyr(Bz₄-β-D-Gal)-OPfp 3, N^α-Fmoc-Tyr(Bz₄-α-D-Gal)-OPfp 4, N^α-Fmoc-Tyr(Bz₃-α-L-Rha)-OPfp 6, N-^α-Fmoc-Tyr[Bz₃-α-L-Rha(1→3)-Bz₃-β-D-Gal]-OPfp 18, and N^α-Fmoc-Tyr[Bz₄-α-D-Glc(1→4)-Bz₃-α-D-Glc(1→4)-Bz₃-β-D-Glc]-OPfp 20, are described. The synthesis involves the coupling of the corresponding glycosyl bromides with the aryl tert-butyl ether N^α- Fmoc-Tyr(Bu^t)-OPfp 1, using silver trifluoromethanesulfonate as promoter.