Solid-phase synthesis and conformational studies of helper T cell immunogenic peptides that carry carbohydrate haptens linked to serine

N ^α-Fmoc serine and its corresponding pentafluorophenyl ester were glycosylated with the 1,2-trans peracetates of the disaccharides galabiose and cellobiose. Complete stereoselectivity and 52-75% yields were obtained under boron trifluoride etherate promotion. Lower yields and loss of stereoselectivity were obtained when thioglycosides. trichloroacetimidates or glycosyl bromides were employed as glycosyl donors. The glycosylated building blocks were used in solid-phase synthesis of derivatives of a helper T cell immunogenic peptide consisting of amino acids 52-61 from hen-egg lysozyme. ¹H-NMR spectroscopy in DMSO-d₆ showed that the peptide moiety of the glycopeptides assumed random conformations which were not influenced by glycosylation at different positions.