1H NMR (DMSO-d6) δ 11.58 (s, 1H), 8.42 (d, J = 8 Hz, 1H), 8.37 (d, J = 8 Hz, 1H), 7.62 (s, 1H), 7.32 (s, 1H), 7.08 (t, J = 8 Hz, 1H), 6.99 (d, J = 8 Hz, 1H), 6.49 (d, J = 8 Hz, 1H), 5.04 (t, J = 8 Hz, 1H), 4.52 (m, 1H), 4.42 (m, 1H), 4.24 (dd, J = 8, 20 Hz, 1H), 4.12 (dd, J = 8, 20 Hz, 1H), 3.87 (s, 3H), 3.09 (m, 2H), 2.25 (m, 1H), 2.06 (m, 1H), 1.93 (m, 1H), 1.80 (dd, J = 8, 16 Hz, 1H), 0.93 (s, 9H); MS (ESI+) for C25H34N4O6m/z 487.2 (M + H)+; anal. calcd for C25H34N4O6·0.3 H2O: C, 61.03; H, 7.09; N, 11.39.