To the solution of methyl 3-[5-(3-{[benzylamino]carbonylamino}propoxy)indolyl]propanoate (80 mg, 0.2 mmol), as prepared in the preceding step, in tetrahydrofuran (5 mL) and water (5 mL) was added sodium hydroxide (20 mg), and the reaction mixture was stirred at ambient temperature for 2 h. After evaporating the tetrahydrofuran, the aqueous solution was acidified (pH 5–6), the white solid formed was collected, washed with water and dried under high vacuum to give the title compound (65 mg, 82%). 1H-NMR (400 MHz, DMSO6) δ 7.21–7.37 (m, 7H), 7.02 (d, J=2.4 Hz, 1H), 6.78 (dd, J=8.8, 2.4 Hz, 1H), 6.36 (t, J=6.0 Hz, 1H), 6.30 (d, J=2.9 Hz, 1H), 6.06 (t, J=5.7 Hz, 1H), 4.34 (t, J=6.8 Hz, 2H), 4.20 (d, J=6.0 Hz, 2H), 3.96 (t, J 6.2 Hz, 2H), 3.19 (q, J=6.4 Hz, 2H), 2.71 (t, J=6.8 Hz, 2H), 1.83 (t, J=6.5 Hz, 2H). Mass spectrum (LCMS, ESI) Calcd. for C22H25N3O4 396.4 (M+H), found: 396.1.
