Combinatorial approach for the design of new, simplified chiral phase-transfer catalysts with high catalytic performance for practical asymmetric synthesis of α-alkyl-α-amino acids

A very efficient, chiral phase-transfer catalyst (S)-2Db was prepared by taking advantage of the combinatorial approach from the known, easily available (S)-1,1′-binaphthyl-2,2′-dicarboxylic acid. This catalyst exhibited the high catalytic performance (0.01–0.1 mol %) in the asymmetric alkylation of N-(diphenylmethylene)glycine tert-butyl ester compared to the existing chiral phase-transfer catalysts, thereby allowing to realize a general and useful procedure for highly practical enantioselective synthesis of structurally diverse natural and unnatural α-alkyl-α-amino acids.