Comparison of the Enantioselectivity of Phenethyl- and Naphthylethyl-Carbamate Substituted Cyclodextrin Bonded Phases

Abstract

(R)-, (S)- and racemic-phenethylcarbamate substituted-β-cyclodextrin bonded stationary phases were prepared and evaluated for the high performance liquid chromatographic separation of enantiomers. The results were compared to corresponding separations on an (S)-(-)-l-(l-naphthyl)ethyl-carbamate substituted β-cyclodextrin bonded phase. Successful separations were obtained in the reversed-phase and normal phase modes as well as with mobile phases of intermediate polarity. Different mechanisms of separation seem to be operative for various classes of compounds, depending upon the polarity of the mobile phase. The columns act as a novel cyclodextrin phase in the reversed phase mode, π-complex-hydrogen bonding chiral stationary phase in the normal phase mode, and cellulosic-like-phase with polar organic solvents such as methanol. With different chromatographic modes, it resolves completely different sets of enantiomers thereby serving as several columns in one.