Highly enantioselective synthesis of α-alkyl-alanines via the catalytic phase-transfer alkylation of 2-naphthyl aldimine tert-butyl ester by using O(9)-allyl-N(1)-2′,3′,4′-trifluorobenzylhydro-cinchonidinium bromide

Systematic investigations to develop an efficient enantioselective synthetic method for alpha-alkyl-alanine by catalytic phase-transfer alkylation were performed. The alkylation of 2-naphthyl aldimine tert-butyl ester, 1E, with RbOH and O(9)-allyl-N-2',3',4'-trifluorobenzylhydrocinchonidinium bromide, 6, at -35degreesC showed the highest enantioselectivities, up to 96% ee.