1.7 mL of methylene chloride, 1.0 μL of N,N-dimethylformamide and 0.025 mL of oxalyl chloride were added to 41 mg of 2,3-dimethylbenzoic acid at room temperature sequentially and stirred at the same temperature for 1 hour. The reaction mixture was added to a mixed solution of 49 mg of tert-butyl 2-amino-4-(2,4-difluorophenyl)benzoate, 2.8 mL of methylene chloride and 0.36 mL of triethylamine and stirred at room temperature for 1 hour. A saturated sodium hydrogen carbonate aqueous solution was added to the reaction mixture, and the organic layer was separated, and the solvent was evaporated under reduced pressure. The obtained residue was purified with silica gel column chromatography [Flash Tube 2008 manufactured by Trikonex Company, eluent; hexane:ethyl acetate=4:1]to obtain tert-butyl 4-(2,4-difluorophenyl)-2-(2,3-dimethylbenzamido)benzoate.
