BigPatents India

- The present invention relates to a process for racemisation of undersired, optically active isomer ( R)-2-(4-chlorophenyl)-3-methylbutanoic acid [(R)-CPMBA] obtained as soluble diastereomeric salt from optical resolution of (±)-CPMBA. The process consists of separating the undesired isomer ( R)-CPMBA from its optically active amine salt solution by concentration under reduced pressure and extraction with aqueous mineral acid. The aqueous mineral acid layer containing optically active resolving amine [(-)-PEA] as salt is treated with caustic lie to recover the optically active amine for reuse in resolution of (±)-CPMBA. The separated undersired isomer (R) –CPMBA is subjected to racemisation by heating in Nitrogen atmosphere at 210-2200C for 8-10 hrs. and purified by distillation at reduced pressure to obtain (±)-CPMBA. Thus, the process described is not only simple for effective use of undersired isomer (R)-CPMBA, but also provides a method for efficient recovery and recycle of optically active resolving agent[(-)-PEA]. Hence it is quite advantageous for industrial application.