Structurally Diverse Diterpenes from the South China Sea Soft Coral Sarcophyton trocheliophorum .

The present investigation of the South China Sea soft coral Sarcophyton trocheliophorum resulted in the discovery of six new polyoxygenated diterpenes, namely sartrocheliols A-E ( 1 , 3 , 5 - 8 ) along with four known ones, 2 , 4 , 9 , and 10 . Based on extensive spectroscopic data analysis, sartrocheliol A ( 1 ) was identified as an uncommon capnosane diterpene, while sartrocheliols B-E ( 3 , 5 - 8 ) were established as cembrane diterpenes. They displayed diverse structural features not only at the distinctly different carbon frameworks but also at the various types of heterocycles, including the epoxide, γ-lactone, furan, and pyran rings. Moreover, their absolute configurations were determined by a combination of quantum mechanical-nuclear magnetic resonance (QM-NMR) approach, modified Mosher's method, and X-ray diffraction analysis. In the anti-tumor bioassay, compound 4 exhibited moderate cytotoxic activities against A549, H1975, MDA-MB-231, and H1299 cells with the IC 50 values ranging from 26.3 to 47.9 μM.