N-((1S)-1-{[((1S)-3-(Benzyloxy)-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)amino]carbonyl}-3-methylbutyl)-4-methoxy-N-methyl-1H-indole-2-carboxamide
Following the procedure described for the preparation of N-[(1S)-2-[((1S)-3-(benzyloxy)-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)amino]-1-(cyclohexylmethyl)-2-oxoethyl]-4-methoxy-1H-indole-2-carboxamide but substituting N1-((1S)-3-(benzyloxy)-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)-N2-(tert-butoxycarbonyl)-N2-methyl-l-leucinamide and making noncritical variations provided a crude brown oil. This material was purified by Biotage flash chromatography, eluting with methanol/dichloromethane to afford the title compound as a clear oil, 67 mg, 48%. 1H NMR (400 MHz, CDCl3) δ 9.83 (s, 1H), 7.95 (s, 1H), 7.26–7.36 (m, 5H), 7.18 (t, J = 8.0 Hz, 1H), 7.04 (d, J = 8.3 Hz, 1H), 7.00 (s, 1H), 6.48 (d, J = 7.8 Hz, 1H), 5.87 (s, 1H), 5.18–5.27 (m, 1H), 4.70 (s, 1H), 4.50–4.63 (m, 2H), 4.16–4.36 (m, 2H), 3.93 (s, 3H), 3.32 (s, 3H), 3.03–3.18 (m, 2H), 2.22 (s, 2H), 1.91–2.02 (m, 1H), 1.81 (t, J = 7.3 Hz, 3H), 1.66–1.72 (m, 1H), 1.55 (s, 1H), 0.87–1.01 (m, 6H); MS (API-ES−) for C32H40N4O6m/z 576.7 (M – H)−.