Enantioselective Desymmetrization of cis-3,5-O-Arylidenecyclohexanones Catalyzed by Cinchona-Derived Quaternary Ammonium Salts

An enantioselective protocol for the desymmetrization of cis-3,5- O-arylidenecyclohexanones has been developed that proceeded under the catalysis of readily available and inexpensive Cinchona-derived quaternary ammonium salts. The synthetic relevance of the methodology was exemplified by the synthesis of a key intermediate that could be used in the preparation of the active pharmaceutical ingredient, paricalcitol (Zemplar).