Polystyrene‐Anchored <i>Cinchona</i> Ammonium Salts: Easily Recoverable Phase‐Transfer Catalysts for the Asymmetric Synthesis of α‐Amino Acids

Abstract

Abstract Cinchonidine, epicinchonidine, cinchonine or quinine have been N ‐anchored to cross‐linked polystyrene (Merrifield resin) or grafted polystyrene (SynPhase TM Lanterns) affording polymer‐supported chiral ammonium salts which are employed as phase‐transfer catalysts in the asymmetric alkylation of N ‐(diphenylmethylene)glycine esters. These new polymeric catalysts can be easily recovered after the reaction by simple filtration and reused.