Structure of Azalomycin B. Structural elucidation of compound 1: Azalomycin B, C54H88O18, white microcrystals. UV (MeOH) λmax 252nm; electrospray ionization (ESI) MS m/z: 1047 [M + Na]+; 1H NMR (600 MHz, MeOD) δH 6.93 (1H, dd, J = 15.2, 11.2 Hz, H-3), 6.17 (1H, dd, J = 15.0, 11.2 Hz, H-4), 5.74 (1H, d, J = 15.4 Hz, H-2), 5.67 (1H, dd, J = 15.1, 9.9 Hz, H-5), 5.04 (2H, m, H-7, H-22), 4.02 (1H, d, J = 9.7 Hz, H-13), 3.94 (2H, m, H-24, H-26), 3.90 (2H, m, H-9, H-15), 3.53 (1H, m, H-25), 2.58 (1H, m, H-6), 2.34 (1H, dd, J = 12.1, 4.5 Hz, H-12), 1.95 (1H, m, H-8), 1.94 (1H, dd, J = 12.3, 3.9 Hz, H-23), 1.72 (1H, m, H-10), 1.66 (1H, m, H-20), 1.62 (1H, dd, J = 12.6, 4.7 Hz, H-23), 1.47 (1H, m, H-20), 1.20 (3H, d, J = 6.6 Hz, H-27), 1.16 (1H, m, H-16), 1.13 (3H, d, J = 6.0 Hz, H-16), 1.12 (1H, m, H-12), 1.05 (3H, d, J = 6.6 Hz, H-17), 0.97 (3H, d, J = 7.1 Hz, H-19), 0.87 (6H, t, J = 6.2 Hz, H-21, H-18). 13C NMR (150 MHz, MeOD) δC 170.4 (C-1), 146.9 (C-3), 146.1 (C-5), 132.7 (C-4), 122.6 (C-2), 100.9 (C-11), 94.8 (C-22), 78.2 (C-7), 72.4 (C-25), 71.8 (C-9), 70.9 (C-13), 68.2 (C-15), 68.1 (C-26), 67.0 (C-24), 49.8 (C-14), 44.0 (C-10), 42.7 (C-6), 38.9 (C-12), 37.8 (C-8), 33.7 (C-23), 20.3 (C-20), 19.5 (C-16), 17.3 (C-27), 15.8 (C-17), 9.6 (C-18), 9.5 (C-21), 7.1 (C-19).