0.27 g (0.66 mmol) of N-{3-(3,4-dimethylphenyl)propyl}-4-(2-aminoethoxy)-3-methoxyphenylacetamide obtained in Step 5 of Example 3, 0.17 g (0.94 mmol) of acetylsalicylic acid and 0.10 g (0.74 mmol) of 1-hydroxylbenzotriazole were dissolved in 15 ml of a mixture of acetonitrile and dimethylformamide(1:2). 0.19 g (0.92 mmol) of dicyclohexanecarbodiimide was added thereto and the resultant mixture was stirred at a room temperature for 2 days. White precipitates were removed and the remaining solution was diluted with 30 ml of dichloromethane, which was washed with water and dried. After removing the solvent under a reduced pressure, the residue was subjected to silica gel chromatography to obtain 0.22 g of the title compound (yield: 63%).
