Patent ID: 7427688

Claim:
A method of producing a diphenylalanine compound represented by formula (4) or a salt thereof, which comprises: (a): reacting a diphenylmethylene halide compound represented by formula (1): wherein R 1 and R 2 are each independently a halogen atom, an alkyl group, an alkoxy group, an amino group, a nitro group or a hydroxyl group, n 1 and n 2 are each independently an integer of 0-5, and X is a chlorine atom, a bromine atom or an iodine atom, with a malonic acid diester compound represented by formula (2): wherein R 3 and R 4 are each independently an alkyl group or an aralkyl group, or R 3 and R 4 in combination form an alkylene group, and P 1 is an amino-protecting group, in at least one organic solvent selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, and mixtures thereof, in the presence of at least one base selected from the group consisting of an alkali metal hydride, an alkali metal t-butoxide, and mixtures thereof, to give a diester compound represented by formula (3): wherein each symbol is as defined above; and (b): subjecting said diester compound to hydrolysis and decarboxylation, to give said diphenylalanine compound represented by formula (4): wherein R 1 , R 2 , n 1 and n 2 are as defined above, and P 2 is a hydrogen atom or an amino-protecting group, or a salt thereof.