Liquid chromatographic enantioseparation of limonene-based carbocyclic β-amino acids on zwitterionic Cinchona alkaloid-based chiral stationary phases.

The eight stereoisomers of limonene-based carbocyclic β-amino acids containing three chiral centers have been directly separated on chiral stationary phases containing Cinchona alkaloid-based zwitterionic selectors. The effects of bulk solvent composition of the mobile phase, the nature of base additives, counterion concentration, and the structure of selector on the enantiorecognition were studied. Experiments were performed at constant mobile phase composition in the temperature range 5-40°C to study the effect of temperature. Thermodynamic parameters were calculated on the basis of the plots of ln α versus 1/T curves. The enthalpically or entropically driven enantioseparations were found to depend strongly on the structures of analyte and selector. The eight stereoisomers of limonene-based carbocyclic β-amino acids could be differentiated as well-separated peaks in a traditional 1D chromatographic system in two runs by applying the two complementary ZWIX(+)™ and ZWIX(-)™ columns.