(R)-NAPHTHYLETHYLCARBAMATE-SUBSTITUTED AND (S)-NAPHTHYLETHYLCARBAMATE-SUBSTITUTED BETA-CYCLO-DEXTRIN BONDED STATIONARY PHASES FOR THE REVERSED-PHASE LIQUID-CHROMATOGRAPHIC SEPARATION OF ENANTIOMERS

(R)- and (S)-naphthylethylcarbamate-beta-cyclodextrin bonded phases were originally developed for the normal-phase separation of enantiomers. Although their selectivity resembled that of some of the earlier substituted cellulosic phases, the functionalized cyclodextrin stationary phases were much more stable as they were bonded to the silica support and not adsorbed. Because of their stability, the naphthyl-ethylcarbamate-beta-cyclodextrin stationary phase was utilized in reversed-phase separations. It was found that a completely different set of enantiomers was resolved by this column in the reversed-phase mode. This included racemic pesticides such as Dyfonate, Ruelene, Ancymidol and Coumachlor; as well as a variety of pharmacologically active compounds such as Tropicamide, Indapamide, Althiazide, Tolperisone, a sulfonamide from Merck Sharp & Dohme that has been resolved only by indirect methods, and over twenty others. It appears that the naphthylethylcarmabate-beta-cyclodextrin bonded phase is a highly effective multimodal chiral stationary phase. The concept of a multimodal chiral stationary phase is discussed. The effect of pH and the configuration of the naphthylcarbamate group is considered as well.