Liquid chromatography with mass spectrometry enantioseparation of pomalidomide on cyclodextrin‐bonded chiral stationary phases and the elucidation of the chiral recognition mechanisms by NMR spectroscopy and molecular modeling

Abstract

A sensitive and validated liquid chromatography with mass spectrometry method was developed for the enantioseparation of the racemic mixture of pomalidomide, a novel, second-generation immunomodulatory drug, using β-cyclodextrin-bonded stationary phases. Four cyclodextrin columns (β-, hydroxypropyl-β-, carboxymethyl-β-, and sulfobutyl-β-cyclodextrin) were screened and the effects of eluent composition, flow rate, temperature, and organic modifier on enantioseparation were studied. Optimized parameters, offering baseline separation (resolution = 2.70 ± 0.02) were the following: β-cyclodextrin stationary phase, thermostatted at 15°C, and mobile phase consisting of methanol/0.1% acetic acid 10:90 v/v, delivered with 0.8 mL/min flow rate. For the optimized parameter at multiple reaction monitoring mode 274.1-201.0 transition with 20 eV collision energy and 100 V fragmentor voltage the limit of detection and limit of quantitation were 0.75 and 2.00 ng/mL, respectively. Since enantiopure standards were not available, elution order was determined upon comparison of the circular dichroism signals of the separated pomalidomide enantiomers with that of enantiopure thalidomide. The mechanisms underlying the chiral discrimination between the enantiomers were also investigated. Pomalidomide-β-cyclodextrin inclusion complex was characterized using nuclear magnetic resonance spectroscopy and molecular modeling. The thermodynamic aspects of chiral separation were also studied.

Recognition of Oligosaccharides by Chirality Induced in Europium (III) Compounds

“…The sensitivity of EuEDTAb inding towardsd ifferent cyclodextrins might thus be useful for various applicationsi ncluding chirals eparations, [19] MRI agents, [20] and asymmetrical catalysis. The sensitivity of EuEDTAb inding towardsd ifferent cyclodextrins might thus be useful for various applicationsi ncluding chirals eparations, [19] MRI agents, [20] and asymmetrical catalysis.…”

“…When within d % 12-14 the two components starts to react, EuEDTAn eeds to loose part of the water hydrations phere, which is connected with an increase (g, b)o rd ecrease (a)o f the free energy.O nlyt he b and g cavities, however,c an fully accommodate the complex. The sensitivity of EuEDTAb inding towardsd ifferent cyclodextrins might thus be useful for various applicationsi ncluding chirals eparations, [19] MRI agents, [20] and asymmetrical catalysis. [21] The predicted dependence of CPL intensity to the binding strength is confirmed by titration curves( Figure S10).…”

Enantioseparation of racecadotril using polysaccharide‐type chiral stationary phases in polar organic mode

“…During chiral separations, temperature changes affect both analyte retention and enantioselective interactions . In order to obtain information about the mechanistic aspects of chiral discrimination process, the differences in the change of standard enthalpy Δ(ΔH°) and standard enthropy Δ(ΔS°) for the 2 enantiomers moving from the mobile to the stationary phase were calculated according to the modified van't Hoff equation: where R is the universal gas constant, T is the temperature, expressed in Kelvin, while α is the selectivity factor.…”

The degree of substitution affects the enantioselectivity of sulfobutylether‐β‐cyclodextrin chiral stationary phases

“…Cyclodextrins (CDs) are cyclic oligosaccharides consisting of six or more D‐glucopyranose units linked in α(1–4). Due to their availability, inexpensiveness and ability to form inclusion complexes , CDs are among the most commonly used chiral selectors for enantioselective separation in various separation techniques, such as HPLC , CE , GC or supercritical fluid chromatography . Especially derivatized CDs often show excellent separation performance .…”