Chromatographic separation of free dafachronic acid epimers with a novel triazole click quinidine-based chiral stationary phase

For the first time, a successful chromatographic method based on the use of a novel triazole click quinidine (QD) derivative anion-exchange chiral stationary phase (CSP) is applied for the epimer separation of dafachronic acids (Δ4- and Δ7-DAs). The use of a polar-ionic eluent system consisting of 18 mM AcOH in ACN furnished an excellent separation of both Δ4- (α = 1.19, RS = 2.52) and Δ7-DA (α = 1.14, RS = 2.06) C-25 epimer couples. The pool of data collected during the chromatographic analyses revealed the prominent role of anion-exchange interactions in governing the analyte (SA) retention and also indicated the occurrence of stereoselective H-bond contacts with the chiral selector (SO) substructural motifs. In any case, molecular modelling studies corroborate the need for sufficient spatial freedom for optimum binding between the SO and the SAs which seems less the case for the immobilised SO unit of the commercialized QD-based CSP.