1-Amino-6-methoxy-3-phenyl-1H-indene-2-carboxylic acid ethyl ester (50 mg, 0.16 mmol) prepared in Example 20 was dissolved in dichloromethane (10 mL), and propionyl chloride (150.38 mg, 0.14 mL, 1.62 mmol) and triethylamine (180.12 mg, 0.25 mL, 1.78 mmol) were added thereto in order at 0° C. The mixture was stirred for 24 hrs at RT, and an excess amount of propionyl chloride (2 mL) was further added thereto to be stirred for 15 hrs. The resulting mixture was washed with saturated saline and extracted with dichloromethane. The organic layer was separated, dried over anhydrous MgSO4 and concentrated under a reduced pressure. The resulting residue was purified by flash chromatography to obtain 29 mg of the titled compound (yield: 50%).
