Small-scale solid-phase O-glycopeptide synthesis of linear and cyclized hexapeptides from blood-clotting factor IX containing O-(α-D-Xyl-1→3-α-D-Xyl-1→3-β-D-Glc)-L-ser

Glycopeptide sequences corresponding to residues 51–56 of the EGF-like domains of human and bovine blood-clotting factor IX have been synthesized using the Fmoc/Dhbt strategy. Building blocks consisting of Fmoc-Ser(R)-OPfp, where R=β-D-Glc or α-D-XyI-(1–3)-α-D-XyI-(1–3)-α-D-Glc, have been synthesized. The building blocks were prepared by treatment of the unprotected glycosylated serine compounds with N-(fluoren-9-ylmethoxycarbonyl)succinimide in 1,4-dioxane, followed by treatment with pentafluorophenol and dicyclohexylcarbodiimide in tetrahydrofuran. The glycosylated building blocks were then used in a solid-phase peptide synthesis to give the corresponding glycopeptides. Cyclic glycopeptides were prepared from the acetamidomethylprotected linear glycopeptides by treatment with thalliunl(III) trifluoroacetate in trifluoroacetic acid. The cyclic glycopeptides were fully characterized by NMR spectroscopy and mass spectrometry.