Stereoselective high-performance liquid chromatography and analytical method characterization of evacetrapib using a brush-type chiral stationary phase: A challenging isomeric separation requiring a unique eluent system

• A brief history of the Whelk-O 1 chiral stationary phase is presented.
• Separation of evacetrapib from three isomers and multiple synthetic impurities.
• Novel eluent system employing a fine-tuned modifier and additive mixture.
• Hypothesis of enantioselective evacetrapib to chiral selector interaction is proposed.

Using HPLC chiral separation screening, various columns representing the polysaccharide, macrocyclic antibiotic and brush classes were assessed in multiple chromatographic modes for the separation of evacetrapib, a potential cardiovascular drug, from its enantiomer, two diastereomers and several impurities. Screening data consistently pointed to the brush-type Whelk-O 1 chiral column as most promising for this task. A systematic separation optimization process is outlined using the (S,S) Whelk-O 1 chiral column, first for the resolution of the isomers, and later including six potential impurities. A relatively complex yet rugged separation system was eventually identified that effectively resolves all compounds within a reasonable analysis time, and should serve as an adequate tool for evacetrapib bulk drug enantiopurity measurement.