Optically Active Polymers for Chiral Separation

One of the most practically important functions of optically active polymers is chiral recognition. In the past two decades, various optically active polymers have been utilized as the chiral stationary phases (CSPs) for high-performance liquid chromatography, which is today the most powerful and practical method not only for analyzing enantiomers but also for obtaining them in a pure form. In this account, the emphasis lies on the polymethacrylate and polysaccharide derivatives that we have developed. One-handed helical poly(triphenylmethyl methacrylate) has been prepared by asymmetric anionic polymerization and shows high chiral recognition, especially for the compounds which have no functional groups. Polysaccharide derivatives, particularly cellulose and amylose phenylcarbamates, can resolve a wide range of racemates, and their abilities are significantly influenced by the substituents introduced on the phenyl moieties. Cellulose and amylose cycloalkylcarbamates and chitin phenylcarbamates also show high chiral recognition; the former can be utilized as the CSPs for thin-layer chromatography because of the absence of UV absorption. The immobilization of the polysaccharide derivatives onto a silica support via chemical bonding improves their durability for various solvents and also their resolving ability for some compounds. Several phenylcarbamates are soluble in chloroform, which allowed one to study their chiral recognition mechanism at a molecular level, particularly by NMR spectroscopy. A computational method can also be applied for mechanistic studies.