To obtain in high yield a compound useful as an intermediate for peptide leukotriene antagonists without using any problematic solvent such as carbon tetrachloride, by photochemical reaction of a 4-methyl-3- methoxybenzoic ester with N-bromosuccinimide in a benzene compound or specific ester.

This compound, a 4-bromomethyl-3-methoxybenzoic ester of formula I (R is a 1-5C alkyl), is obtained by reaction of (A) a 4-methyl-3- methoxybenzoic ester of formula II with (D) N-bromosuccinimide in (B) chlorobenzene or (C) an ester of the formula, R2-COOR3 (R2 is H or a1-3C alkyl; R3 is a 1-4C alkyl) at -10 to 120°C while irradiating the reaction system with rays of light 10-5-10-8m in wavelength. In is preferable that the reaction is carried out in the presence of (E) a radical-forming agent, (F) chlorobenzene, methyl formate, ethyl formate, methyl acetate, ethyl acetate or n-propyl acetate.