4-Methoxy-N-((1S)-1-{[((1S)-3-methoxy-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)amino]carbonyl}-3-methylbutyl)-1H-indole-2-carboxamide (48)
A solution of N-((1S)-1-{[((1S)-3-hydroxy-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)amino]carbonyl}-3-methylbutyl)-4-methoxy-1H-indole-2-carboxamide (185 mg, 0.39 mmol), iodomethane (0.12 mL, 2.0 mmol), and silver(I) oxide (182 mg, 0.79 mmol) in dichloromethane (12 mL) was placed under an atmosphere of N2. The resulting black thick suspension was heated to reflux for 18 h, treated with a second portion of iodomethane (0.12 mL, 2.0 mmol), and returned to reflux for an additional 24 h. The reaction was cooled to RT, diluted with dichloromethane (20 mL), washed once with water (20 mL), once with brine (20 mL), dried over MgSO4, filtered, and concentrated to give a crude tan solid. This material was purified by Biotage MPLC (25 M column, 3.5–4.5% methanol/chloroform) to afford 19 mg (10%) of the title compound as an off-white solid. 1H NMR (DMSO-d6) δ 11.57 (s, 1H), 8.48 (d, J = 8 Hz, 1H), 8.40 (d, J = 8 Hz, 1H), 7.63 (s, 1H), 7.35 (s, 1H), 7.08 (t, J = 8 Hz, 1H), 6.99 (d, J = 8 Hz, 1H), 6.49 (d, J = 8 Hz, 1H), 4.47 (m, 1H), 4.38 (m, 1H), 4.25 (d, J = 16 Hz, 1H), 4.11 (d, J = 16 Hz, 1H), 3.87 (s, 3H), 3.23 (s, 3H), 3.08 (m, 2H), 2.31 (m, 1H), 2.08 (m, 1H), 1.92 (m, 1H), 1.72–1.51 (m, 5H), 0.93 (d, J = 8 Hz, 3H), 0.88 (d, J = 8 Hz, 3H); MS (ESI+) for C25H34N4O6m/z 487.2 (M + H)+; HRMS (ESI+) calcd for C25H34N4O6+H1 487.2551, found 487.2563.