New trimeric Cinchona alkaloid-based quaternary ammonium salts as efficient chiral phase transfer catalysts for enantioselective synthesis of α-amino acids

New trimeric quaternary ammonium salts derived from cinchonine or cinchonidine bridging N,N′-bis(ethyl)-4-(methyl)-phenyl-amine moiety are used as a chiral phase transfer catalysts for the asymmetric alkylation of a N-(diphenylmethylene)glycine tert-butyl ester with very good chemical yield (up to 97%) and ee's (up to 98%).

Graphical abstractNew trimeric Cinchona alkaloid-based quaternary ammonium salts as efficient chiral phase transfer catalysts for enantioselective synthesis of α-amino acids. Figure optionsDownload full-size imageDownload as PowerPoint slide