Separation and quantitation of eight isomers in a molecule with three stereogenic centers by normal phase liquid chromatography.

A normal phase liquid chromatography method was developed for the separation and detection of eight stereoisomers of the key intermediate, CORE + OMe, having three chiral centers. The stereochemistry of this intermediate dictates the stereochemistry of the active pharmaceutical ingredient generated by an additional six synthetic steps. Multiple columns and mobile phases were screened during the development based on a platform approach. The use of dichloromethane as mobile phase additive and adjustment of flow rate and column temperature contributed in achieving resolution of these eight stereoisomers. The separation and detection of these stereoisomers was achieved using a Chiralcel OD-H, 4.6 × 250 mm, 5 µm dp column with heptane: ethanol: dichloromethane in a ratio of 95:3:2 (v:v:v) as mobile phase at a flow rate of 0.7 mL/min. UV detection was carried out at 245 nm and the column temperature was maintained at 15 °C. The analytical method was phase appropriately validated. The limit of detection and limit of quantification were found to be 0.035 and 0.07 µg, respectively. The newly developed method has been implemented for routine utilization to monitor the chiral control during process development and used as the quality control method for chiral purity of the desired compound.