title: Synthesis, crystal structure and molecular conformation of the tBuCO-D,L-Ala-delta Z-Phe-NHiPr alpha,beta-unsaturated dipeptide.
abstract: The crystal structure of the tBuCO-D,L-Ala-delta Z-Phe-NHiPr dipeptide has been solved by X-ray diffraction. The peptide crystallizes in monoclinic space group P2(1)/c with a = 13.445 (3) A, b = 35.088 (4) A, c = 14.755 (3) A, beta = 116.73 (1) degree, Z = 12 and dc = 1.151 g.cm-3. The three independent molecules per asymmetric unit accommodate a beta II-folded conformation, but only one of them contains the typical i + 3----i interaction characterizing a beta-turn. In the other two molecules, the N...O distance exceeds 3.2 A, a value generally considered the upper limit for hydrogen bonds in peptides. In solution, the beta II-turn conformation is largely predominant.
authors.affiliation: URA-CNRS-809, University of Nancy I, Vandoeuvre, France.
authors.forename: A
authors.initials: A
authors.lastname: Aubry
authors.forename: G
authors.initials: G
authors.lastname: Pietrzynski
authors.forename: B
authors.initials: B
authors.lastname: Rzeszotarska
authors.forename: G
authors.initials: G
authors.lastname: Boussard
authors.forename: M
authors.initials: M
authors.lastname: Marraud
mesh_terms: D004151:Dipeptides / Q000138:chemical synthesis* / Q000737:chemistry; D006860:Hydrogen Bonding; D015394:Molecular Structure; D011487:Protein Conformation; D012996:Solutions; D014961:X-Ray Diffraction
chemical_list: D004151:Dipeptides; D012996:Solutions