In the course of our search for bioactive metabolites from Japanese marine invertebrates, we encountered two sponges, Acanthella klethra and Haliclona sp., which showed marked activity in antifungal and starfish egg assays. Bioassay-guided isolation afforded four new cytotoxic compounds; two new diterpene isonitriles named kalihinene (1) and isokalihinol B (2) along with the known compound kalihinol A (3) from A. klethra and two macrocyclic alkaloids, haliclamines A (4) and B (5) from Haliclona sp. Structures of isocyanoditerpenes were deduced mainly by interpretation of 500MHz NMR spectra including COSY, NOE and decoupling experiments as well as by comparison of spectral data with those of kalihinols. Kalihinene was found to contain a unique cis-dehydro-decalin system. Kalihinene and isokalihinol B were not only antifungal but also cytotoxic against P388 leukemia cells with IC_<50> 1.2 and 0.8μg/mL, respectively. Structure elucidation of haliclamines was done by extensive 500MHz NMR analyses including COSY, HMBC, NOESY and decoupling experiments in different solvents as well as by HREIMS analyses. Finally, the structures were confirmed by dehydrogenation with Pd-C. Haliclamines A and B inhibited not only cell division of fertilized sea urchin eggs at 5 and 10μg/mL, respectively, but also growth of L1210 and P388 leuekemia cells at IC_<50> 1.5 and 0.9, and 0.75 and 0.39μg/mL, respectively.
