Kalihinene-A [ 171 and kalihinene-B [ 181 two new toxic isocyano diterpenes have been isolated from a Seychelles specimen of the marine sponge Acuntl~ella cavemosa. Their structures were elucidated by interpretation of their spectral properties. The chemotaxonomic value of these secondary metabolites is discussed.Marine sponges of the genus Acaritliella are characterized by the presence of isocyano terpenes sometimes accompanied by the corresponding isothiocyanate and formamide derivatives. lsocyano sesquiterpenes have been reported from A. aczira (Mediterranean A. kleflira (Australia)(5s6), A. pzrlcherrinia (Australia)('), A. cf cavemosa (Japan)(8) and A. sp (Northeast Pacific)('), and isocyano diterpenes from A . cuvemosa (Fiji(l0'") and Thailand(12)), A. kletlira (Japan)(13) andA. sp (Guam) (10,14 .Interestingly, the species A . carteri (syn. A. auraritiaca) differs from the other members of the genus in that it contains pyrroloaminopropylimidazole alkaloids(1"") instead of isocyano terpenes.The isocyano diterpenes found in Acaritliella sponges are highly functionalized tricyclic derivatives named kalihinols. Structurally, the kalihinols fall into two main groups, the tetrahydropyran kalihinols [l-71 and the tetrahydrofuran kalihinols [8-151. In addition, a monounsaturated kaiihinane (kalihinene [IS]) has been isolated from a Japanese sample of A. kletIira(l3). Among others, the latterdiffersfrom the kalihinols inthat it possessa cis-rather than atrans-fused decalin system. Several of these diterpenes show a broad spectrum of biological activities, including antimicrobial("), anthelmintic(' c y t o t~x i c (~~) and antifungaP3) properties.*Author to whom correspondence may be addressed.
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R iIn the course of our continuing search for biologically active and taxonomically significant secondary metabolites in sponges, specimens of A. cavemosa and A. caHeri were collected by SCUBA diving during a collecting cruise of one of the authors (R.V.S.) in the Seychelles Islands. Their secondary metabolite contents were investigated and -187 -
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