Enantioselective synthesis of (S)-4-methyleneglutamic acid via tandem conjugate addition–elimination under phase-transfer catalytic conditions

An efficient enantioselective synthetic method for (S)-4-methyleneglutamic acid is reported. Phase-transfer catalytic conjugate addition–elimination of the benzophenone imine of glycine tert-butyl ester in the presence of chiral Cinchona-derived catalysts give the corresponding conjugated addition products (>99% ee), which could be hydrolyzed to chiral (S)-4-methyleneglutamic acid.