LAUSR

Diclazuril has been widely used in poultry feed for prevention and treatment of coccidiosis, and its chiral separation is rarely reported. Herein, semi-preparative separation method of diclazuril enantiomers has been developed through normal-phase HPLC. Effects of chiral stationary phases, alcoholic modifiers, and column temperature on separation of diclazuril were discussed in detail. Both the single-urea-bound 4-chlorophenylcarbamoylated β-cyclodextrin and amylose tris(3,5- dimethylphenylcarbamate)-coated chiral stationary phases showed strong ability in separation of diclazuril through using n-hexane-TFA-ethanol. Then, semi-preparative separation of diclazuril was carried out through stacked injection, and the enantiomeric excess purities of two fractions were over 98%. Next, the electronic circular dichroism profiles of these two fractions in ethanol solution displayed the mirror image of each other in the range 360∼200 nm. Moreover, effects of acidic/basic additive, time, and temperature on racemization of diclazuril enantiomers in ethanol solution have been studied in detail through normal-phase HPLC. Racemization of diclazuril enantiomers was remarkably accelerated through adding triethylamine at high temperature. We envision that this systematic investigation of diclazuril at an enantiomeric level would provide valuable information in future studies involving enantioselective bioactive, metabolic, and toxicological activities. This article is protected by copyright. All rights reserved.