Separation of tetrahydrozoline enantiomers in capillary electrophoresis with cyclodextrin-type chiral selectors and investigation of chiral recognition mechanisms

The recognition power and affinity pattern of various cyclodextrins (CD) towards the enantiomers of tetrahydrozoline (THZ) were studied using capillary electrophoresis (CE). As expected, affinity of THZ enantiomers and selectivity of recognition towards CD derivatives was strongly dependent on the cavity size and substituent type and pattern on the CD rims. Not only were the affinity strength and selectivity of recognition affected by the size of the cavity and chemistry of the CDs but also the affinity pattern. Another interesting example of opposite affinity pattern of enantiomers towards alpha- and beta-CD was observed here. In addition, opposite affinity pattern of THZ enantiomers was seen towards beta-CD and its acetylated derivatives, while methylation of beta-CD did not affect the affinity pattern of THZ enantiomers. In order to get more information about structural mechanisms of the multivariate dependences mentioned above, rotating frame Overhauser enhancement spectroscopy (ROESY) and computation techniques were used. Significant differences between the structure of THZ complexes with different CDs with both methods were encountered. Good correlations between experimentally determined and computed structure of complexes, as well as between computed complex stabilities and enantiomer migration order (EMO) in CE were observed. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the recognition power and affinity patterns of various cyclodextrins towards the enantiomers of tetrahydrozoline using capillary electrophoresis. The affinity and selectivity were strongly influenced by the cavity size and substituent type on the cyclodextrin rims. It was also found that enantiomers exhibited opposite affinity patterns towards different cyclodextrins.