Comparative enantioseparations with native beta-cyclodextrin,randomly acetylated beta-cyclodextrin and heptakis-(2,3-di-O-acetyl)-beta-cyclodextrin in capillary electrophoresis

Comparative enantioseparations were performed with three neutral cyclodextrins (CDs) in capillary electrophoresis (CE). In particular, native beta-CD was compared with single component heptakis(2,3-di-O-acetyl)-beta-CD (HDA-beta-CD) and randomly acetylated beta-CD (Ac-beta-CD) with the emphasis on the enantiomer migration order. The opposite affinity of the enantiomers of several chiral analytes was observed towards native beta-CD and its acetylated derivatives. The enantiomer affinity pattern of some chiral analytes was also opposite towards the two acetylated derivatives of beta-CD. In the case of the chiral drug clenbuterol (CL) an attempt was made to evaluate the possible structural reasons of the affinity reversal using one- and two-dimensional as well as transverse rotating frame nuclear Overhauser effect spectroscopy (ROESY). Significant differences were observed between the structure of the CL complexes with beta-CD and HDA-beta-CD.