Enantioseparation of benzazoles and benzanilides on polysaccharide-based chiral columns.

The chiral recognition ability of the polysaccharide-based chiral columns (Chiralpak AD-RH, Chiralpak AS-RJ, Chiralpak IC, Chiralcel OD-RH, and Chiralcel OJ-RH) for the benzazoles and the benzanilides was evaluated under reversed phase conditions. The columns showed the high chiral recognition ability for a wide range of benzazoles and benzanilides. Twenty-one racemates were used for the evaluation, and 20 racemates were completely separated on at least one of the columns. In particular, AS-RH and OJ-RH showed the high chiral recognition ability for the benzazoles, and the AD-RH, IC, and OJ-RH were effective for the benzanilides.

High-performance liquid chromatographic enantioseparations on capillary columns containing crosslinked polysaccharide phenylcarbamate derivatives attached to monolithic silica.

Monolithic capillary columns containing native silica gel were covalently modified with 3,5-disubstituted phenylcarbamate derivatives of cellulose and amylose and applied for enantioseparations in capillary LC. The method previously used for covalent immobilization of polysaccharide phenylcarbamate derivatives onto the surface of microparticulate silica gel was successfully adapted for in situ modification of monolithic fused-silica capillary columns. The effects of the nature of polysaccharide and the substituents, as well as of multiple covalent immobilization of polysaccharide derivative on chromatographic performance of capillary columns were studied. The capillary columns obtained using this technique are stable in all solvents commonly used in LC and exhibit promising enantiomer resolving ability.

Preparation of chiral stationary phase for HPLC based on immobilization of cellulose 3,5-dimethylphenylcarbamate derivatives on silica gel.

The immobilization of cellulose 3,5-dimethylphenylcarbamate derivatives having a polymerizable vinyl group, i.e., 4-vinylphenylcarbamate or 2-methacyloyloxyethylcarbamate, on silica gel was examined under various conditions. The immobilization was basically conducted through the radical copolymerization of the derivatives with a vinyl monomer. Several factors, such as the vinyl monomer content and the type and amount of the vinyl group of cellulose derivatives, were varied. The introduction of a vinyl group onto the silica surface resulted in a more efficient immobilization of the cellulose phenylcarbamate derivatives on the silica gel. As the content of the vinyl group on the cellulose derivatives was reduced, the immobilization became more difficult, although the obtained phase exhibited higher chiral recognition abilities. These immobilized CSPs could be stably used with the eluent containing 10% chloroform, which cannot be used for the phase prepared by coating the derivatives on silica gel. Some racemates were better resolved on the immobilized CSP by using chloroform as a component of the eluent.

Reversed-phase liquid chromatographic enantioseparation by cycloalkylcarboxylates of cellulose and amylose.

Three novel cycloalkylcarboxylates, cyclopentyl, cyclohexyl, and 1-adamantylcarboxylates of cellulose and amylose were prepared and their chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were evaluated using a methanol-water mobile phase. Among these esters, cellulose tris(cyclohexylcarboxylate) showed a relatively high chiral recognition ability. The 1-adamantylcarboxylates of cellulose and amylose showed dissimilar chiral recognition abilities from the other two, probably due to the low degree of substitution and the high hydrophobicity of this group.