Cembrane diterpenoids from the Taiwanese soft coral Sinularia flexibilis

Chemical investigation of the soft coral Sinularia flexibilis (Quoy and Gaimard), collected from the southern coast of Taiwan, led to the isolation of 10 new cembrenoid diterpenoids, the flexilarins A–J (1–10), along with 17 known compounds (11–27). The structures of these compounds were elucidated by spectroscopic techniques (NMR, MS, UV, IR). The structure of compound 1 was confirmed by X-ray crystallographic analysis. Compound 4 exhibited potent cytotoxicity against Hep2 tumor cells.