Structure–Chiral Selectivity Relationships of Various Mandelic Acid Derivatives on Octakis 2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin Containing Gas Chromatographic Stationary

Abstract

Frequently, a good chiral separation is the result of long trial and error processes. The three-point interaction mechanisms require the fair geometrical fitting and functional group compatibility of the interacting groups. Structure–chiral selectivity correlations are guidelines that can be established via trough systematic studies using model compounds. The enantiorecognition of the test compounds was studied on an octakis 2,3-Di-O-acetyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin (TBDMSDAGCD) chiral selector. In our work, mandelic acid and its variously substituted compounds were used as model compounds to establish adaptable rules for other enantiomeric pairs. The mandelic acid and its modified compounds were altered at both their carboxyl and hydroxyl positions to test the key interaction forces of the chiral recognition processes. Ring- and alkyl-substituted mandelic acid derivatives were also used in our experiments. The chiral selectivity values of 20 test compounds were measured and extrapolated to 100 °C. The hydrogen donor abilities of test compounds improved their chiral selectivities. The inclusion phenomenon also played a role in chiral recognition processes in several cases. Enantiomer elution reversals were observed for different derivatives of hydroxyl groups, providing evidence for the multimodal character of the selector. The results of our research can serve as guidelines to achieve appropriate chiral separation for other enantiomeric pairs.