Trifluoroacetic acid → 2-({4-[2-(4-Iodophenoxy)ethyl]-1,3-thiazol-2-yl}thio)-2-methylpropionic acid methyl ester

2-({4-[2-(4-Iodophenoxy)ethyl]-1,3-thiazol-2-yl}thio)-2-methylpropionic acid tert-butyl ester (6.0 g) obtained in Example 144-1 was dissolved in dichloromethane (25 mL), trifluoroacetic acid (20 mL) was added, and the mixture was stirred at room temperature for 12 hr. The reaction mixture was concentrated under reduced pressure, and the residue was dissolved in methanol (60 mL). Thionyl chloride (5.63 g) was added under ice-cooling and the mixture was refluxed for 4 hr. The reaction mixture was concentrated under reduced pressure, saturated aqueous sodium hydrogen carbonate solution was added, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified by silica gel chromatography (elution solvent; hexane:ethyl acetate=6:1 to 4:1) to give the title compound (5.2 g) as a colorless oil.