Enantioselective Synthesis of (R)-α-Alkylhomoserines and (R)-α-Alkylhomocysteines via Phase-Transfer Catalytic Alkylation

Efficient enantiosclective synthetic methods for (R)-alpha-alkylhomoserines and (R)-alpha-alkylhomocysteines have been developed. The phase-transfer catalytic alkylation of 2-phenyl-5,6-di-hydro-4H-1,3-oxazine-4-carboxylic acid tert-butyl ester and 2-phenyl-5,6-dihydro-4H-1,3-thiazine-4-carboxylic acid tert-butyl ester, in the presence of N-2',3',4'-trifluorobenzyleinchonidinium bromide, gave the corresponding alkylated products, which Could be hydrolyzed to provide (R)-alpha-alkylhomoserines (up to 97% ee) and (R)-alpha-alkylhomocysteines (up to 91% ee), respectively.