Studies directed toward the synthesis of protein-bound GPI anchor

Abstract Mannobioside-linked phosphoethanolamine 10 , a prototype model of the GPI anchor, was synthesized via glycosidation of the monosaccharide donor and acceptor, and subsequent phosphorylation. In order to test the reactivity of the amino group involved in 10 against the activated amino acid esters, 10 was reacted with N -protected amino acid pentafluorophenyl esters in the presence of HOBt. The reactions gave the aminoacylated products in moderate yields. When Fmoc-Ser-OPfp 12 and Fmoc-Cys(SBu t )-OPfp 14 were reacted with 10 , byproducts 19 , 20 and 21 derived from N - and O -acylation were produced. In contrast, reactions of 10 and N -protected amino acid thioesters were promoted with AgNO 3 , HOSu, and DIEA to afford the coupling products without the undesired O -acylation. Peptidylation of 10 with the synthesized oligopeptide thioesters 24 and 27 was also successful under the segment coupling conditions of the peptide thioester method as well as those of the native chemical ligation.