title: Structural variations in the crystal structures of two homologous DL-Leu and delta-Leu containing peptides.
abstract: The similar conformations and interaction modes of Ac-DL-Leu-NMe2 and Ac-delta-Leu-NMe2 molecules in the solid state allow the comparison of their geometrical parameters. The most evident variations are essentially restricted to the alpha, beta-unsaturated side-chain which adopts the Z-disposition. The dimensions of the peptide backbone are much less sensitive to alpha, beta-unsaturation, with a small shortening by 0.04 A and 0.02 A of the N--C alpha and C alpha--C' bonds, respectively, and an increase by 6 degrees of the N--C alpha--C' bond angle. The ethylenic and amide groups in the delta-Leu derivative are far from coplanarity, and a significant electronic conjugation of the pi-orbital is likely to be rejected.
authors.affiliation: URA-CNRS-809, University of Nancy, France.
authors.forename: L
authors.initials: L
authors.lastname: el-Masdouri
authors.forename: A
authors.initials: A
authors.lastname: Aubrey
authors.forename: G
authors.initials: G
authors.lastname: Boussard
authors.forename: M
authors.initials: M
authors.lastname: Marraud
mesh_terms: D003460:Crystallization; D006860:Hydrogen Bonding; D007930:Leucine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D010455:Peptides; C079674:acetyl-N-dimethyl-alpha,beta-dehydroleucinamide; C079673:acetyl-N-dimethylleucinamide; D007930:Leucine