this study, we wish to report another example of the exception to the successful application of the reciprocity conception of chiral recognition observed during the process of checking the enantioselectivities exerted by two CSPs based on (S)-N-(2,2-dimethyl-4-pentenoyl)proline-3,5-dimethylanilide 1 (Figure 1) and (S)-N-(2,2-dimethyl-4pentenoyl)proline-3,5-dimethoxyanilide 2 (Figure 1). Previously, a CSP (CSP 3, Figure 1) based on (S)-N-(2,2-dimethyl-4-pentenoyl)proline-3,5-dimethylanilide 1 was reported excellent in the separation of the enantiomers of N(3,5-dinitrobenzoyl)-α-amino amides and esters. 5 Thereafter, a CSP (CSP 4, Figure 1) based on (S)-N-(2,2-dimethyl4-pentenoyl)proline-3,5-dimethoxyanilide 2 was also developed based on the reciprocity conception of chiral recognition in order to utilize in the preparative chromatographic separation of the enantiomers of the chiral selectors used in commercial CSPs. 6 However, the exact comparison of the two CSPs on the basis of the reciprocity conception of chiral recognition has not been reported. In our own study, we found that racemic N-(2,2-dimethyl4-pentenoyl)proline-3,5-dimethoxyanilide 2 was resolved better (k1 = 5.41, k2 = 45.88, α = 8.48) than racemic N-(2,2dimethyl-4-pentenoyl)proline-3,5-dimethylanilide 1 (k1 = 2.00, k2 = 14.00, α = 7.00) on a CSP based on N-(3,5-dinitrobenzoyl)leucine N-allyl amide. The stronger π-π interaction between the relatively more π-basic 3,5-dimethoxyphenyl group of analyte 2 and the π-acidic 3,5-ninitrobenzoyl group of the CSP compared to that between the relatively less πbasic 3,5-dimethylphenyl group of analyte 1 and the π-acidic 3,5-ninitrobenzoyl group of the CSP is believed to be responsible for the longer retention and the greater enantioselectivity of analyte 2. Consequently, we expected that CSP Figure 1. Structures of N-(2,2-dimethyl-4-pentenoyl)proline-3,5dimethylanilide 1, N-(2,2-dimethyl-4-pentenoyl)proline-3,5-dimethoxyanilide 2, CSP 3 and CSP 4.