COMPARISON OF N-DTS AND N-ALOC IN THE SOLID-PHASE SYNTHESES OF O-GLCNAC GLYCOPEPTIDE FRAGMENTS OF RNA-POLYMERASE-II AND MAMMALIAN NEUROFILAMENTS

The application of the glycosylated building blocks N-alpha-Fmoc-Ser(Ac-3-beta-D-GlcNAc)-OPfp 5, N-alpha-Fmoc-Thr(Ac-3-beta-D-GlcNAc)-OPfp 6, N-alpha-Fmoc-Ser(Ac-3-beta-D-GlcNDts)-OPfp 7 and N-alpha-Fmoc-Thr(Ac-3-beta-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-H-1 NMR spectroscopy and ES-MS.