Abstract: The present invention provides a catalyst system and a process for stereoselectively inverting a chiral center of a chemical compound. The catalyst system of the present invention comprises (i) a catalytic amount of a metal catalyst; (ii) an enzyme capable of oxidizing a chemical compound at a chiral center, or microorganism cells capable of producing an enzyme which is capable of oxidizing a chemical compound at a chiral center; (iii) an oxidant; and (iv) a hydrogen source. The process of the present invention comprises treating a chemical compound having a chiral center with the catalyst system of this invention.