To a solution of 5-[2-[N-tert-butoxycarbonyl-2-(2-ethoxyphenoxy)ethylamino]propyl]indoline-7-carbonitrile (120 mg) in dimethyl sulfoxide (2.5 ml) was added 30% hydrogen peroxide (0.26 ml), and the mixture was stirred at room temperature for 15 minutes. Then, to the reaction mixture was added a 5N sodium hydroxide solution (0.26 ml), and the mixture was stirred at room temperature for 1.5 hours. To the reaction mixture was added acetic acid. The mixture was diluted with water and extracted with ethyl acetate. The extract was washed with a saturated aqueous sodium bicarbonate solution and water, dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give 127 mg of 5-[2-[N-tert-butoxycarbonyl-2-(2-ethoxyphenoxy)ethylamino]propyl]indoline-7-carboxamide as an oil.
