title: Conformations of peptides containing a chiral cyclic α, α-disubstituted α-amino acid within the sequence of Aib residues.
abstract: A single chiral cyclic α,α-disubstituted amino acid, (3S,4S)-1-amino-(3,4-dimethoxy)cyclopentanecarboxylic acid [(S,S)-Ac(5)c(dOM)], was placed at the N-terminal or C-terminal positions of achiral α-aminoisobutyric acid (Aib) peptide segments. The IR and (1)H NMR spectra indicated that the dominant conformations of two peptides Cbz-[(S,S)-Ac(5)c(dOM)]-(Aib)(4)-OEt (1) and Cbz-(Aib)(4)-[(S,S)-Ac(5)c(dOM)]-OMe (2) in solution were helical structures. X-ray crystallographic analysis of 1 and 2 revealed that a left-handed (M) 3(10)-helical structure was present in 1 and that a right-handed (P) 3(10)-helical structure was present in 2 in their crystalline states.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Demizu
authors.forename: Masakazu
authors.initials: M
authors.lastname: Tanaka
authors.forename: Mitsunobu
authors.initials: M
authors.lastname: Doi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kurihara
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Okuda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suemune
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000621:Aminoisobutyric Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003515:Cycloleucine / Q000031:analogs & derivatives* / Q000737:chemistry; D006860:Hydrogen Bonding; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000596:Amino Acids; D000621:Aminoisobutyric Acids; D010455:Peptides; D003515:Cycloleucine; C100049:2-aminoisobutyric acid