title: Conformations of helical Aib peptides containing a pair of L-amino acid and D-amino acid.
abstract: A pair of L-leucine (L-Leu) and D-leucine (D-Leu) was incorporated into a-aminoisobutyric acid (Aib) peptide segments. Thedominant conformations of four hexapeptides, Boc-L-Leu-Aib-Aib-Aib-Aib-L-Leu-OMe (1a), Boc-D-Leu-Aib-Aib-Aib-Aib-L-Leu-OMe(1b), Boc-Aib-Aib-L-Leu-L-Leu-Aib-Aib-OMe (2a), and Boc-Aib-Aib-D-Leu-L-Leu-Aib-Aib-OMe (2b), were investigated by IR,¹H NMR, CD spectra, and X-ray crystallographic analysis. All peptides 1a,b and 2a,b formed 3₁₀-helical structures in solution. X-ray crystallographic analysis revealed that right-handed (P) 3₁₀-helices were present in 1a and 1b and a mixture of right-handed(P) and left-handed (M) 3₁₀-helices was present in 2b in their crystalline states.
authors.affiliation: Division of Organic Chemistry, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan. demizu@nihs.go.jp
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Demizu
authors.forename: Yu-U
authors.initials: YU
authors.lastname: Yabuki
authors.forename: Mitsunobu
authors.initials: M
authors.lastname: Doi
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Sato
authors.forename: Masakazu
authors.initials: M
authors.lastname: Tanaka
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kurihara
mesh_terms: D000621:Aminoisobutyric Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007930:Leucine / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000621:Aminoisobutyric Acids; D009842:Oligopeptides; C100049:2-aminoisobutyric acid; D007930:Leucine