Enantioseparation of chiral benzimidazole derivatives by electrokinetic chromatography using sulfated cyclodextrins

Baseline separation of 18 new substituted benzimidazole derivatives, potent AMP-activated protein kinase (AMPK) activators, with one chiral center, was achieved by CD-EKC using sulfated and highly sulfated CDs (SCDs and HS-CDs) as chiral selectors. The influence of the type and concentration of the chiral selectors on the enantioseparations was investigated. The SCDs exhibit a very high enantioselectivity power since they allow excellent enantiomeric resolutions compared to those obtained with the neutral CDs. The enantiomers were resolved with analysis times around 6 min using 25 mM phosphate buffer at pH 2.5 containing either beta-S-CD, HS-beta-CD, HS-gamma-CD (3 or 4% w/v) at 25 degrees C, with a voltage of 20 kV. The apparent association constants of the inclusion complexes were calculated. The study of the solute structure-enantioseparation relationships seems to show the high contribution of the interactions between the solutes phenyl ring and the CDs to the enantiorecognition process. The optimized method was briefly validated (LOD less than 1%) and the purity of enantiomers of compound 3 was determined. The enantiomer migration shows reversal order depending on the kind of CD.