Chiral Discrimination on Polysaccharides Derivatives

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Abstract
Chromatographic enantioseparations, particularly resolution by high-performance liquid chromatography (HPLC), have advanced considerably in the past decade, and have become a practically useful method not only for determining their optical purity, but also for obtaining optical isomers. The preparation of a chiral stationary phase (CSP) capable of effective chiral recognition is the key to this separation technique. We have found that polysaccharide derivatives, particularly cellulose esters and phenylcarbamate derivatives of cellulose and amylose, are very effective CSPs, and can resolve a wide range of racemates, including drugs. A variety of polysaccharides derivatives involving tribenzoates and tris(phenylcarbamates) of cellulose and amylose were prepared and their chiral recognition abilities were evaluated as CSPs in HPLC. The chiral recognition and resolving ability of the derivatives depend greatly on the substituents introduced on the phenyl moieties. The introduction of electron-donating or electron-withdrawing substituents improved the chiral recognition ability. Among the many derivatives of polysaccharides, 3,5-dimethylphenylcarbamates of cellulose and amylose and cellulose tris(4-methylbenzoate) show high chiral recognition, which has allowed the resolution of more than 80% of the racemates tested. These CSPs can be used for both analytical and preparative separations of enantiomers. Some significant mechanistic aspects are also briefly reviewed.

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