title: beta-Alanyl-beta-alanine in cyclic beta-turned peptides.
abstract: In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(L-Pro-L-Pro-L-Phe-beta-Ala-beta-Ala). The peptide was synthesized by classical solution methods and the cyclization of the free pentapeptide was accomplished in good yields in diluted methylene-chloride solution using N,N-dicyclohexylcarbodiimide. The compound crystallizes in the monoclinic space group P21 from hot water with five solvent molecules. The Pro1-Pro2 peptide bond is cis and the molecular conformation is stabilized by an intramolecular hydrogen bond between the CO group of the beta-Ala5 and the NH of the Phe3 residue. The Pro1-Pro2 segment occupies the relative positions 2 and 3 of a type VIa beta-turn, while the L-phenylalanyl-beta-alanyl-beta-alanine segment is incorporated in a C13-like ring structure. The crystal packing is characterized by a network of 11 intermolecular hydrogen bonds involving all the remaining CO, NH, and the water molecules.
authors.affiliation: Department of Chemistry, Università Federico II, Napoli, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Di Blasio
authors.forename: A
authors.initials: A
authors.lastname: Lombardi
authors.forename: X
authors.initials: X
authors.lastname: Yang
authors.forename: C
authors.initials: C
authors.lastname: Pedone
authors.forename: V
authors.initials: V
authors.lastname: Pavone
mesh_terms: D003461:Crystallography; D047630:Depsipeptides; D008958:Models, Molecular; D008968:Molecular Conformation; D010456:Peptides, Cyclic / Q000737:chemistry*; D015091:beta-Alanine / Q000737:chemistry*
chemical_list: D047630:Depsipeptides; D010456:Peptides, Cyclic; D015091:beta-Alanine; C010324:roseotoxin B; C040424:destruxin B