“…The 1 H, 13 C, and HSQC NMR revealed the presence of a ketone carbonyl carbon ( δ C 209.9), two ester carbonyl carbons ( δ C 170.0 and δ C 169.5), three pairs of C=C double bonds [ δ C / δ H 135.2 (C-8), 135.1 (C-15), 130.3 (C-11)/5.20 (H-11, t, J = 6.3 Hz), 129.3 (C-12), 125.7 (C-7)/4.98 (H-7, m), and 124.8 (C-3)/5.73 (H b -3, d, J = 2.5 Hz), 6.42 (H a -3, d, J = 2.5 Hz)], two oxymethines [ δ C / δ H 80.2 (C-2)/4.97 (H-2, d, J = 3.5 Hz), 75.6 (C-14)/5.09 (H-14, dt, J = 11.0, 2.5 Hz)], three tertiary methyls [ δ H 2.02 (H-14-OAc, s), 1.72 (H-20, s), and 1.49 (H-19, s)], and a secondary methyl at δ H 1.14 (H-18, d, J = 7.0 Hz) (Table 2). Detailed analysis of these NMR data suggested that 2 also displayed a type IIa cembranoid skeleton and was closely related to a previously reported compound, (1 S ,2 S ,3 E ,7 E ,11 E )-3,7,11,15-cembratetraen-17,2-olide [80], with a missing C=C double bond moiety, as well as additional groups of a ketone carbonyl ( δ C 209.9) and an acetyl [ δ C / δ H 170.0, 21.0/2.02 (s)]. According to the HMBC cross-peaks (from H-18 and H-2 to C-3; from H-2 to C-14), two additional oxygen bearing groups were added into the main 14-membered ring system, a ketone group at C-3 and an acetyl group at C-14 (Figure 4).…”