title: Conformational mimicry. II. An obligatory cis amide bond in a small linear peptide.
abstract: The structure of Z-Pro psi [CN4]-Ala-OBzl has been determined by X-ray crystallographic techniques. The structure crystallizes in space group P2(1) with cell constants a = 22.176(3) A, b = 6.141(1)A, c = 8.275(1) A, beta = 98.31(1), and Z = 2. The structure has been refined to a residual of 0.038 for 2538 independent data. The amide bond between the prolyl and alanyl residues is cis, a result of the presence of the tetrazole ring system, as is the urethane bond linking the benzyloxycarbonyl and the prolyl groups. A comparison of the structures in this study to other structures containing cis amide bonds shows that the tetrazole ring system, when incorporated into peptides, mimics a cis amide bond. Changes in the distance between the alpha-carbons adjacent to the tetrazole rings in the linear peptide as compared with the bicyclic diketopiperazine required a reassessment of the conformational mimicry with the cis amide bond.
authors.affiliation: Medical Foundation of Buffalo, Inc. NY.
authors.forename: G D
authors.initials: GD
authors.lastname: Smith
authors.forename: J
authors.initials: J
authors.lastname: Zabrocki
authors.forename: T A
authors.initials: TA
authors.lastname: Flak
authors.forename: G R
authors.initials: GR
authors.lastname: Marshall
mesh_terms: D000577:Amides / Q000737:chemistry*; D000595:Amino Acid Sequence; D004151:Dipeptides / Q000737:chemistry*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D013237:Stereoisomerism; D014961:X-Ray Diffraction
chemical_list: D000577:Amides; D004151:Dipeptides; D009842:Oligopeptides; C070151:benzyloxycarbonyl-prolyl-psi(CN4)-alanine benzyl ester