(3S)-3-({N-[(4-Methoxy-1H-indol-2-yl)carbonyl]-l-leucyl}amino)-2-oxo-4-[(3S)-2-oxopyrrolidin-3-yl]butyl 4-Cyano-2-fluorobenzoate (25)
Following the procedure described for the preparation of (3S)-3-({N-[(4-methoxy-1H-indol-2-yl)carbonyl]-l-leucyl}amino)-2-oxo-4-[(3S)-2-oxopyrrolidin-3-yl]butyl acetate but substituting 4-cyano-2-fluorobenzoic acid and making noncritical variations provided a crude oily brown solid. This material was purified by Biotage MPLC (25 M, 2.5–3.5% methanol/dichloromethane) to afford 119 mg (48%) of the title compound as an off-white powder. 1H NMR (DMSO-d6) δ 11.58 (d, J = 2 Hz, 1H), 8.63 (d, J = 8 Hz, 1H), 8.46 (d, J = 8 Hz, 1H), 8.06 (m, 2H), 7.83 (d, J = 8 Hz, 1H), 7.65 (s, 1H), 7.36 (d, J = 2 Hz, 1H), 7.08 (t, J = 8 Hz, 1H), 6.99 (d, J = 8 Hz, 1H), 6.50 (d, J = 8 Hz, 1H), 5.16 (d, J = 16 Hz, 1H), 5.11 (d, J = 16 Hz, 1H), 4.49 (m, 2H), 3.87 (s, 3H), 3.11 (m, 2H), 2.32 (m, 1H), 2.10–1.98 (m, 2H), 1.77–1.53 (m, 5H), 0.94 (d, J = 6 Hz, 3H), 0.89 (d, J = 6 Hz, 3H); MS (ESI+) for C32H34FN5O7m/z 620.1 (M + H)+; anal. calcd for C32H34FN5O7·0.3 H2O: C, 61.49; H, 5.58; N, 11.20. Found: C, 61.47; H, 5.61; N, 10.98; HRMS (ESI+) calcd for C32H34FN5O7+H1 620.2515, found 620.2532.