New flexible cembrane-type macrocyclic diterpenes as TNF-α inhibitors from the South China Sea soft coral Sarcophyton mililatensis

A further study on the rarely reported soft coral Sarcophyton mililatensis disclosed five new flexible cembrane-type macrocyclic diterpenes sarcomililatols C-G (1-5) and two known analogues 6 and 7. The structures and absolute configurations of natural macrocyclic compounds 1-6 were established by the extensive spectroscopic analysis, X-ray diffraction analysis, time-dependent density functional theory/electronic circular dichroism (TDDFT ECD) calculations, chemical reaction, and modified Mosher's method. In the bioassays, the macrocyclic diterpene 2 exhibited potent TNF-α inhibition (IC