Polymer-Supported Cinchona Alkaloid-Derived Ammonium Salts as Recoverable Phase-Transfer Catalysts for the Asymmetric Synthesis of ÃŽÂ±-Amino AcidsAuthor(s): Rafael Chinchilla | Patricia MazÃƒÂ³n | Carmen NÃƒÂ¡jera
Journal: Molecules ISSN 1420-3049
Volume: 9; Issue: 5; Start page: 349; Date: 2004;
Keywords: Amino acids | asymmetric synthesis | phase-transfer catalysis | chiral ammonium salts.
Alkaloids such as cinchonidine, quinine and N-methylephedrine have been N-alkylated using polymeric benzyl halides or co-polymerized and then N-alkylated, thus affording a series of polymer-supported chiral ammonium salts which have been employed as phase-transfer catalysts in the asymmetric benzylation of an N-(diphenylmethylene)glycine ester. These new polymeric catalysts can be easily recovered by simple filtration after the reaction and reused. The best eeÃ¢Â€Â™s were achieved when Merrifield resin-anchored cinchonidinium ammonium salts were employed.