Methyl Substituent Effects on the Complexation Behavior of 1-(1-Phenylethoxy)-2-pyridone with [beta]-Cyclodextrin

We analyzed UV absorption, circular dichroism, and 1H-NMR spectra of the 1 : 1 inclusion complexes formed between β-cyclodextrin (β-CDx) and racemic 1-(1-phenylethoxy)-2-pyridone and its methyl derivatives. The phenyl moiety in the guests turned out to be preferentially immersed into the β-CDx cavity leaving the pyridone chromophore around the rim of the secondary hydroxy group side. In addition, it was shown that the methyl substituent introduced at the 6 position of the pyridone ring exerts its effect so as to increase the stability of β-CDx inclusion complex formed. However, the β-CDx cavity exhibited a poor chiral recognition ability for racemic 1-(1-phenylethoxy)-2-pyridone, while its ability underwent methyl substituent effects to only a very small extent.