Synthesis and characterisation of highly glycosylated glycopeptides with Tn-antigenic structures corresponding to human glycophorin AN

Two highly glycosylated O-glycopeptides corresponding to human glycophorin AN with Tn-antigenic structures were synthesised. The first glycopeptide has two glycosylated clusters with three and six adjacent 2-acetamido-2-deoxy-d-galactose (GalNAc) glycosylation sites and represents the N-terminal octadecapeptide from Leu-1 to Lys-18. The second glycopeptide, a decapeptide from His-9 to Lys-18, contains as a compact cluster six adjacent GalNAc glycosylation sites. The solid phase synthesis was realised by using the carbohydrate-containing building blocks Fmoc-Ser(Ac3GalN3)-Pfp and Fmoc-Thr(Ac3GalN3)-Pfp. The synthesised substances were characterised by NMR spectroscopic techniques. The main techniques used were homonuclear TOCSY and NOESY as well as HMQC and HMBC for 13C, 1H correlations.