title: Blood group antigens: synthesis of TN glycopeptide related to human glycophorin AM.
abstract: Three 2-acetamido-2-deoxy-alpha-D-galactopyranose residues attached to Ser2, Thr3 and Thr4 of the amino-terminal portion of glycophorin AM are responsible for the so-called TN blood group specificity. In a continuation of earlier work, this report describes the first chemical synthesis of the triglycosylated pentapeptide H2N-Ser1-Ser2*-Thr3*-Thr4*-Gly5-OH, in which (*) represents the 2-acetamido-2-deoxy-alpha-D-galactopyranosyl residue. This compound constitutes the G1-G5 sequence of the amino-terminal portion of human glycophorin AM, the main erythrocyte membrane glycoprotein. The above compound was obtained by a stepwise peptide coupling strategy alternatively using aminoacids and adequately protected and/or activated O-glycosyl-aminoacids. Since the desired sequence possesses both unglycosylated and glycosylated serine this route was preferred to that in which the glycosylation is carried out on the preformed pentapeptide H2N-Ser-Ser-Thr-Thr-Gly-OH. Carbohydrate residues were introduced into the sequence as 2-azido-2-deoxy-alpha-D-galactopyranosyl-L-serine and L-threonine derivatives. The azido functions were further converted into the corresponding acetamido groups by treatment of the final triglyco-pentapeptide with sodium borohydride in the presence of nickel chloride followed by acetylation.
mesh_terms: D000595:Amino Acid Sequence; D001789:Blood Group Antigens; D002240:Carbohydrate Sequence; D006020:Glycopeptides / Q000138:chemical synthesis*; D006021:Glycophorins; D006801:Humans; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D009904:Optical Rotation; D012795:Sialoglycoproteins
chemical_list: D001789:Blood Group Antigens; D006020:Glycopeptides; D006021:Glycophorins; D007202:Indicators and Reagents; D012795:Sialoglycoproteins