Capillary zone electrophoretic chiral discrimination using a cationic cyclodextrin derivative: Determination of velocity and association constants ofeach enantiomer of the amino acid derivative with 6-trimethylammonio-deoxy-beta-cyclodextrin

A positively charged beta -cyclodextrin possessing a trimethylammonio group , 6-trimethyl-ammonio-6-deoxy-beta -cyclodextrin chloride 1 was prepared by the reaction of an amino derivative 3 with methyl iodide under very mild c onditions. The cyclodextrin derivative discriminated between enantiomers of acetylphenylalanine 2 on capillary zone electrophoresis (CZE) analysis, wh ich was possibly due to an electrostatic interaction between the trimethyla mmonio group of 1 and the carboxylate group of 2, and also due to the inclu sion of 2 in a hydrophobic molecular cavity of 1. Double data normalization based on relative electrophoretic velocity of peaks due to indirect respon se of 1 and also water in an injected sample may be effective for eliminati on of variation and fluctuation of physical parameters of medium, such as v iscosity and ionic strength, in order to determine intrinsic association co nstants and velocity of the complexes.