Conformational studies of cyclo(L-Phe-L-Pro-Gly-L-Pro)2 by 1H- and 13C-nuclear magnetic resonance spectroscopy, and its enantioface-differentiating ability.
Analyses of the 1H- and 13C-nuclear magnetic resonance (1H- and 13C-NMR) spectra of the cyclooctapeptide cyclo (L-Phe-L-Pro-Gly-L-Pro)2 (3) in CDCl3 with the aid of the C-H correlated spectroscopy (C-H COSY) two-dimensional NMR spectrum (Fig. 2) suggested that two kinds of C2-symmetric conformation with all trans and cis-trans-trans-trans forms coexist. When 0.5 eq of CsSCN or 1 eq of D- and L-PheOMe.HCl (D/L ratio = 1/2) was added to a solution of the cyclooctapeptide (3) in CDCl3, the 1H- and 13C-NMR spectra (Fig. 3) suggested the presence of only one C2-symmetric conformation (all trans), resulting from the formation of complexes with CsSCN or D- and L-PheOMe.HCl. The 13C-NMR spectra of the complexes of the cyclooctapeptide (3 or 4) with D- and L-PheOMe.HCl displayed separate resonances for each carbon atom of D-PheOMe.HCl and L-PheOMe.HCl. Furthermore, the ability of 3 to distinguish the D from the L enantiomer, is superior to that of 4 (Table II).
Ishizu
T
T
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Hiroshima, Japan.
Fujii
A
A
Noguchi
S
S
D000595:Amino Acid Sequence; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D013237:Stereoisomerism
D009842:Oligopeptides; D010456:Peptides, Cyclic