title: Lysyl dipeptide and tripeptide model systems for racemization studies in amino acid and peptide chemistry.
abstract: Four series of diastereomeric peptide pairs (X-Lys, Lys-Y, Gly-X-Lys, and Gly-Lys-Y; where X and Y = Ala, Leu, Val, Ile, Phe, and Pro) have been synthesized by conventional procedures using benzyl-based protecting groups. Chromatographic separation of each pair, except Gly-Lys-Pro, has been achieved by elution from a 15-cm Aminex A-5 resin column using pH 5.5 buffer for tripeptides, pH 6.5 buffer for dipeptides, and pH 7.5 buffer for phenylalanyl peptides. The isomers have been identified by chromatography of the L-L isomers. Examples of the use of the model peptides for optical purity determinations and as tests for racemization are presented. The series Gly-X-Lys allows comparison of the tendencies to racemize of residues X during couplings. The separations of other peptides where Y = MeVal and X = N- and O-methylhydroxyamino acids are also described.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D008239:Lysine; D008956:Models, Chemical; D009842:Oligopeptides / Q000138:chemical synthesis; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D009842:Oligopeptides; D008239:Lysine