An oven-dried 40 mL scintillation vial with a spinbar was charged with acetic acid (27 mg, 0.46 mmol) followed by a solution of N-((1S)-1-{[((1S)-3-chloro-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)amino]carbonyl}-3-methylbutyl)-4-methoxy-1H-indole-2-carboxamide (172 mg, 0.35 mmol) in DMF (3.5 mL) and purged with N2. This pale yellow solution was then treated with CsF (122 mg, 0.81 mmol), sealed with a Teflon-lined screwcap, and heated at 65 °C on a reaction block with vigorous stirring. After 3 h, the reaction was cooled to RT, diluted with water (30 mL), and extracted with dichloromethane (4 × 7 mL). The combined organic layers were washed with water (2 × 20 mL), brine (20 mL), and concentrated in vacuo. This material was purified by Biotage MPLC (25 M, 2.5–4.5% methanol/dichloromethane) to afford 78 mg (45%) of the title compound as a white solid. 1H NMR (400 MHz, DMSO-d6) δ 11.57 (s, 1H), 8.57 (d, J = 7.8 Hz, 1H), 8.43 (d, J = 7.6 Hz, 1H), 7.64 (s, 1H), 7.36 (d, J = 1.8 Hz, 1H), 7.08 (t, J = 8.0 Hz, 1H), 6.99 (d, J = 8.1 Hz, 1H), 6.49 (d, J = 7.6 Hz, 1H), 4.83 (d, J = 3.0 Hz, 1H), 4.76–4.95 (m, 1H), 4.35–4.50 (m, 2H), 3.87 (s, 3H), 3.03–3.17 (m, 2H), 2.22–2.35 (m, 1H), 2.09–2.22 (m, 1H), 2.07 (s, 3H), 1.90–2.04 (m, 1H), 1.65–1.77 (m, 2H), 1.48–1.65 (m, 3H), 0.94 (d, J = 6.3 Hz, 3H), 0.89 (d, J = 6.3 Hz, 3H); MS (ESI+) for C26H34N4O7m/z 515.2 (M + H)+. Anal. calcd for C26H34N4O7·0.65 H2O: C, 59.34; H, 6.76; N, 10.65. Found: C, 59.41; H, 6.63; N, 10.68.