(3S)-3-({N-[(4-Methoxy-1H-indol-2-yl)carbonyl]-l-leucyl}amino)-2-oxo-4-[(3S)-2-oxopyrrolidin-3-yl]butyl 2,6-Dichlorobenzoate (22)
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 2,6-dichlorobenzoic acid and making noncritical variations provided a crude product. This material was purified by LC (20 g 230–400 SiO2, 3% methanol/chloroform) to afford 114 mg (65%) of the title compound as a white solid. 1H NMR (DMSO-d6) δ 11.57 (d, J = 2 Hz, 1H), 8.62 (d, J = 8 Hz, 1H), 8.46 (d, J = 4 Hz, 1H), 7.65–7.53 (m, 4H), 7.36 (s, 1H), 7.08 (t, J = 8 Hz, 1H), 6.99 (d, J = 8 Hz, 1H), 6.49 (d, J = 8 Hz, 1H), 5.19 (d, J = 20 Hz, 1H), 5.15 (d, J = 20 Hz, 1H), 4.51 (m, 2H), 3.87 (s, 3H), 3.11 (m, 2H), 2.30 (m, 1H), 2.06 (m, 2H), 1.76–1.51 (m, 5H), 0.94 (d, J = 8 Hz, 3H), 0.89 (d, J = 8 Hz, 3H); MS (ESI+) for C31H34Cl2N4O7m/z 645.1 (M + H)+; Anal. Calcd for C31H34Cl2N4O7·0.2 H2O: C, 57.36; H, 5.34; N, 8.63. Found: C, 57.23; H, 5.55; N, 8.46. HRMS (ESI+) calcd for C31H34Cl2N4O7+H1 645.1877, found 645.1871.