Described are improved phase-transfer catalyzed processes for the higher-yield enantioselective synthesis of precursors for alpha-alkyl amino acids. The alpha-alkylation of N-blocked amino acid esters is carried out with alkyl chlorides or bromides (and benzyl analogues thereof) using novel quaternary ammonium derivatives of chinchonine and chinchonidine. These novel enantioselective catalysts comprise N-substituted, O-substituted cinchoninium or cinchonidinium chlorides or bromides, or 3a,3b-dihydro N-substituted, O-substituted cinchoninium or cinchonidinium chlorides or bromides, where the N-substituent is alkylaryl, and wherein the alkyl contains 1-5 carbon atoms and the aryl has up to thirty carbons, and the O-substituent is alkyl or alkenyl, each having up to about ten carbon atoms. Also involved in this improved process is the use of combinations of solvents, high-speed mixing and below ambient temperatures. The novel precursor starting materials for the alpha-alkyl amino acids are also described.
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