Comparison of N-Dts and N-Aloc in the solid-phase syntheses of O-GlcNAc glycopeptide fragments of RNA-polymerase II and mammalian neurofilaments

Abstract

The application of the glycosylated building blocks Nα-Fmoc-Ser(Ac3-β-D-GlcNAc)-OPfp 5, Nα-Fmoc-Thr(Ac3-β-D-GlcNAc)-OPfp 6, Nα-Fmoc-Ser(Ac3-β-D-GlcNDts)-OPfp 7 and Nα-Fmoc-Thr(Ac3-β-D-GlcNDts)-OPfp 8 in the solid-phase synthesis of O-GlcNAc glycopeptides from the C-terminal domain repeating unit of RNA-polymerase II and the NF-L chain of mammalian neurofilaments is described. The removal of the N-dithiasuccinoyl (N-Dts) amino-protecting group was achieved rapidly and quantitatively by thiolysis with 2-sulfanylethanol or dithiothreitol after the incorporation of the building blocks into the resin-bound peptide. The O-GlcNAc glycopeptides 9–11, 13 and 15–21 were synthesised in good yields by comparative studies employing any of the building blocks 5–8. The O-GlcNAc glycopeptides were fully characterised by 1D- and 2D-1H NMR spectroscopy and ES-MS.