Trifluoroacetic acid → 2-[(4-{2-[(5-Ethylpyrimidin-2-yl)(heptyl)amino]ethyl}-1,3-thiazol-2-yl)thio]-2-methylpropionic acid

2-[(4-{2-[(5-Ethylpyrimidin-2-yl)(heptyl)amino]ethyl}-1,3-thiazol-2-yl)thio]-2-methylpropionic acid tert-butyl ester (6.20 g) obtained in Example 265-2 was dissolved in dichloromethane (60 mL), trifluoroacetic acid (12 mL) was added, and the mixture was stirred at room temperature for 20 hr. The reaction mixture was concentrated under reduced pressure, ethyl acetate was added, and the mixture was washed with saturated aqueous sodium hydrogen carbonate solution (the objective compound was extracted in the ethyl acetate layer). The ethyl acetate layer was washed with aqueous 10% citric acid solution and 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=1:1 to 0:1) to give the title compound (4.50 g) as a colorless oil.