Conformational Studies of Cyclo(L-Phe-L-Pro-Gly-L-Pro)_2 by ^1H- and ^<13>C-Nuclear Magnetic Resonance Spectroscopy, and Its Enantioface-Differentiating Ability

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Analyses of the ^1H- and ^<13>C-nuclear magnetic resonance (^1H- and ^<13>C-NMR) spectra of the cyclooctapeptide cyclo (L-Phe-L-Pro-Gly-L-Pro)_2 (3) in CDCl_3 with the aid of the C-H correlated spectroscopy (C-H COSY) two-dimensional NMR spectrum (Fig. 2) suggested that two kinds of C_2-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 CDCl_3,the ^1H- and ^<13>C-NMR spectra (Fig. 3) suggested the presence of only one C_2-symmetric conformation (all trans), resulting from the formation of complexes with CsSCN or D- and L-PheOMe・HCl. The ^<13>C-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).
公益社団法人日本薬学会の論文
1993-02-15