Optical resolution and enantiomeric purity determination of the analgesic cizolirtine

The optical resolution of (±)-cizolirtine was accomplished with excellent results (>99% ee) by means of crystallization with (+)- or (−)-di-p-toluoyltartaric acid. The optical purity of the samples was controlled by three independent methods: 1H NMR, capillary electrophoresis (CE) (using β-cyclodextrins as chiral resolving agents), and HPLC (using a glycoproteic column). The use of a rapid analytical technique like 1H NMR for estimating the relative amounts of each enantiomer, together with the high sensitivity of CE, afforded a convenient strategy for monitoring the entire process leading to enantiopure compounds. Chirality 11:63–69, 1999.