Conformations of peptides containing a chiral cyclic α, α-disubstituted α-amino acid within the sequence of Aib residues.
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.
Demizu
Yosuke
Y
Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Tanaka
Masakazu
M
Doi
Mitsunobu
M
Kurihara
Masaaki
M
Okuda
Haruhiro
H
Suemune
Hiroshi
H
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
D000596:Amino Acids; D000621:Aminoisobutyric Acids; D010455:Peptides; D003515:Cycloleucine; C100049:2-aminoisobutyric acid