13-Epi-9-Deacetylxenicin Derivatives from a Taiwanese Soft Coral Asterospicularia laurae and Treir Cytotoxic Activity

The xenicane-type diterpene 13-epi-9-deacetylxenicin ( 1 ) was isolated from polar extract of the soft coral Asterospicularia laurae . The structure of 13-epi-9-deacetylxenicin was determined by X-ray diffraction analysis, and the absoulte configuration was determined using the modified Mosher′s method. Eleven acylation products of 13-epi-9-deacetylxenicin were prepared: 13-epi-9- O -p-anisoylxenicin ( 2 ), 13-epi-9- O -2-furoylxenicin ( 3 ), 13-epi-9- O -2-thiophenecarbonylxenicin ( 4 ), 13-epi-9- O -2-benzoylxenicin ( 5 ), 13-epi-9- O -p-toluoylxenicin ( 6 ), 13-epi-9- O -4-chlorobenzoylxenicin ( 7 ), 13-epi-9- O -4-fluorobenzoylxenicin ( 8 ), 13-epi-9- O -4-propylbenzoylxenicin ( 9 ), 13-epi-9- O -4-nitrobenzoylxenicin ( 10 ), and 13-epi-9- O -cinnamoylxenicin ( 11 ) are new compounds, and one known compound, 13-epixenicin ( 12 ). The structures of the new metabolites were determined on the basis of extensive spectroscopic analysis, particularly mass spectroscopy and 2D NMR ( 1 H– 1 H COSY, HMQC, HMBC, and NOESY) spectroscopy. The in vitro cytotoxic activities of the twelve compounds were evaluated against Molt4, K562, U937, and SUP-T1 human tumor cell lines.