Chromatographic separation of several sets of aromatic position isomers on three cellulose- and one amylose-based chiral stationary phases was performed to evaluate the potential of a polysaccharide-based chiral stationary phase (CSP) in the separation of isomeric or closely similar molecules, and to understand the interaction mechanism of this type of CSP with analytes. Their ability of molecular recognition was quite outstanding, but the selection rule was particular to each polysaccharide derivative. In the series of analytes, cellulose tris(4-methylbenzoate) and tris(3,5-dimethylphenylcarbamate) exhibited a contrasting selection rule, and the recognition mechanism was considered based on the computer-simulation of the former polymer.

A series of polysaccharide-based chiral stationary phase (CSP) columns, Daicel Chiralpak IA, IB, and IC, were applied in the separation of the nonenantiomeric isomers of various organometallic compounds and were found to be highly effective in recognizing isomers of minor structural differences. The CSP columns have succeeded to separate the double-bond regioisomers in bridged (η⁵-formylcyclopentadienyl)manganese(I) dicarbonyl complexes 1a/1b, the structural isomers of methylbutenylferrocene derivatives in 2a/2b and 3a/3b, and the geometrical isomers of the (2-methyl-2-butenyl)ferrocenes in (Z)/(E)-3b. Due to the close similarity of the isomeric compounds in these mixtures, separations of the components are extremely difficult and could not be attained by conventional methods such as silica gel column chromatography, silica gel HPLC, recrystallization, distillation/sublimation, etc. Clearly, the polysaccharide-based CSP columns have unique advantages in separation/purification technology, and this study has shown potential usefulness of the CSP columns in separation of not only enantiomeric but also nonenantiomeric mixtures.

To understand the selectivity of the crown ether type chiral stationary phase (CSP), the retention selectivity for aniline and the positional isomers of substituted anilines were studied. In various substituted isomers, except nitroaniline, a remarkable decrease of retention due to steric hindrance was observed for the 2-substituted isomer. To determine the detailed molecular recognition mechanism, quantum chemical calculations were performed for the aggregates between the crown ether and the anilines. The results suggested that the 20-Crown-6, which includes a phenyl-substituted 1,1′-binaphthyl moiety, interacts with alkyl and aryl amines in an unconventional form different from the proposed one for 18-Crown-6.

Daicel Chiralpak IA, IB, and IC, which are the polysaccharide-based chiral stationary phase (CSP) columns for high-performance liquid chromatography (HPLC), were applied in the separation of the non-enantiomeric isomeric mixtures obtained by the various allylation reactions and were highly effective in separating the regio- and (E)/(Z)-isomers in the allylation products. Due to the close structural similarity of the isomeric allylic compounds in the reaction mixtures, separations of the isomers are laborious and could not be accomplished by the conventional methods such as silica gel column chromatography, silica gel HPLC, preparative GPC, distillation, and so forth. This study has shown potential advantages of using the polysaccharide-based CSP columns in the separation of not only enantiomeric but also non-enantiomeric isomeric mixtures.

多糖誘導体系キラル固定相が，幅広い光学異性体化合物群に対して，極めて高いキラル識別能力を有することは既によく知られている。現在の光学純度測定手法の主流はHPLC 法であり，そこでは多糖誘導体系キラルカラムが専ら使用されているとの報告もある。一方，トリグリセリドに代表される油脂系化合物はキラル分離困難な化合物として考えられていたが，ここ数年，分離報告例が相次いだ。ここでは本分野の方にキラル分離を知って頂くためにHPLCキラル分離と多糖誘導体系キラル固定相の概略を振り返るとともに，最近の状況について解説する。