Nitrogen-containing verticillene diterpenoids from the Taiwanese soft coral Cespitularia taeniata

Extensive column chromatography of the ethanolic extract of the soft coral Cespitularia taeniata collected in Taiwan has resulted in the isolation of eight new nitrogen-containing verticillene diterpenes, designated cespitulactams D-K ( 1- 8), together with three known diterpenes, cespitulactams A ( 9) and B ( 10) and cespitularin F. In addition, one new derivative, 6- O-acetylcespitulactam F ( 11), was prepared from compound 3. The structures of these compounds were elucidated on the basis of spectroscopic analyses, especially HRMS and 2D NMR experiments. The cytotoxicity against human oral epidermoid carcinoma (KB) and murine L1210 leukemia cell lines and antimicrobial activities of 1- 8 and 11 were tested and evaluated. A biogenetic pathway for these novel diterpene alkaloids was also proposed.