Solution structures of 1:1 complexes of oxyphenonium bromide with beta- and gamma-cyclodextrins.
The solution structures of complexes of oxyphenonium bromide (OB) with beta- and gamma-cyclodextrins (beta- and gamma-CDs, respectively) in deuterium oxide have been investigated by 500 MHz proton NMR spectroscopy and molecular mechanics calculations. The chemical shifts induced by complex formation provide the 1:1 binding constants and the chemical shift variations, DeltadeltaOB-CD, with complexation for the protons of OB and the CDs. The observed binding constants are very close to those obtained by other methods and are in the following order: beta-CD > gamma-CD > alpha-CD. Initial structures of the complexes are constructed on the basis of the ROESY spectra and the DeltadeltaOB-CD values and are optimized by molecular mechanics calculations. The intermolecular distances between the protons of OB and CD calculated for these structures are well-correlated with the observed ROESY intensities. The cyclohexyl group of OB penetrates deeply into a beta-CD cavity, and the phenyl group is close to the wide rim of the cavity. The phenyl and cyclohexyl groups of OB are both incorporated into a gamma-CD cavity. Furthermore, these structures of the complexes are consistent with the suppression of bitter taste and basic hydrolysis of OB by CDs and the polarity of binding sites of OB.
Funasaki
Noriaki
N
Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. funasaki@mb.kyoto-phu.ac.jp
Sumiyoshi
Tomoko
T
Ishikawa
Seiji
S
Neya
Saburo
S
D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010115:Oxyphenonium / Q000737:chemistry*; D012996:Solutions; D047392:beta-Cyclodextrins / Q000737:chemistry*; D047408:gamma-Cyclodextrins / Q000737:chemistry*
D012996:Solutions; D047392:beta-Cyclodextrins; D047408:gamma-Cyclodextrins; D010115:Oxyphenonium; C031215:betadex