2.3.8. Xanthoquinodin B4 (**8**)

Yellow, amorphous solid; [α] 20 <sup>D</sup> + 540.2◦ (*c* 0.005, MeOH); UV (MeOH) λmax (log ε) 202 (4.4), 274 (3.9), 352 (4.3); CD (*c* 1.5 <sup>×</sup> 10–3 M, MeOH) <sup>λ</sup>max (Δε) 227 (+15.00), 263 (+1.74), 324 (+14.12), 357 (+14.60); 1H-NMR (500 MHz, CDCl3): δ<sup>H</sup> 2.11 (1H, m, H-4a), 2.24 (1H, m, H-4b), 2.39 (3H, s, H-16 ), 2.60 (1H, d, *J* = 18.0 Hz, H-15 b), 2.68 (2H, m, H-5), 2.73 (1H, d, *J* = 18.0 Hz, H-15 a), 3.73 (3H, s, 15-OCH3), 4.4 (1H, dd, *J* = 12.5, 5.0 Hz, H-3), 4.55 (1H, s, H-1 ), 4.83 (1H, d, *J* = 6.0 Hz, H-11 ), 6.10 (1H, s, H-11), 6.47 (1H, d, *J* = 8.5 Hz, H-13 ), 6.51 (1H, dd, *J* = 8.5, 6.5 Hz, H-12 ), 6.78 (1H, s, H-5 ), 6.80 (1H, s, H-3 ), 11.05 (1H, s, 10-OH), 11:28 (1H, s, 6 -OH), 13.95 (1H, s, 6-OH);13C NMR (125 MHz, CDCl3): δ<sup>C</sup> 22.0 (CH3, 16 -CH3), 23.8 (CH2, CH2-4), 27.7 (CH2, CH2-5), 35.3 (CH2, CH2-15 ), 39.0 (CH, CH2-11 ), 42.8 (C, C-14 ), 53.2 (CH3, 15-OCH3), 71.6 (CH, CH2-3), 73.5 (CH, CH-1 ), 85.3 (C, C-2), 101.6 (C, C-7), 105.0 (C, C-9), 105.3 (C, C-14 ), 111.1 (C, C-7 ), 114.1 (CH, CH-11), 115.4 (C, C-13), 119.0 (CH, CH-5 ), 122.1 (CH, CH-3 ), 131.9 (CH, CH-12 ), 132.9 (CH, CH-13 ), 140.6 (C, C-2 ), 147.9 (C, C-4 ), 148.0 (C, C-12), 160.0 (C, C-10), 161.7 (C, C-6 ), 169.9 (C, C-15), 178.5 (C, C-6), 183.9 (C, C-8 ), 186.7 (C, C-8), 188.2 (C, C-10 ); ESI-MS: *m*/*z* 573.15 (M <sup>−</sup> H) <sup>−</sup> and 575.21 (M + H)+; HRESIMS *m*/*z* 575.1547 (M + H)<sup>+</sup> (calculated for C31H27O11, 575.1548).
