N,N-Dimethylaminopyridine (0.7 g, 5.7 mmol) and di-tert-butyl dicarbonate [(tBuOCO)2O] (16.7 g, 76.5 mmol) were added to a solution of 2-hydroxy-6-methyl-3-(trifluoromethyl)benzoic acid (4.21 g, 19.1 mmol) obtained in Example (28-3) in a mixture of tert-butyl alcohol-tetrahydrofuran (2:1, 60 ml), and the mixture was stirred at 60° C. for 3 hours. The reaction mixture was concentrated under reduced pressure and the residue was purified by silica gel column chromatography (eluting solvent: n-hexane/ethyl acetate=9/1) to give tert-butyl 2-[(tert-butoxycarbonyl)oxy]-6-methyl-3-(trifluoromethyl)benzoate (6.27 g, yield: 87%).
