Diterpene isothiocyanates

Kalihinols G (277) and H (278) were trace components of a species of Acanthella from Guam and kalihinol X (279) was isolated from a Fijian species of Acanthella. All inhibited growth of Bacillus subtilis, Staphylococcus aureus and Candida albicans [278]. 10-Epi-isokalihinol H (280) and 15-isothiocyanato-l-epi-kalihinene (281) were isolated from Acanthella cavernosa from the Seychelles [279]. A Japanese specimen of A. cavernosa contained a sesquiterpene isothiocyanate (282) and 10 3-formamido-5p-isothiocyanatokalihinol A (283). Structures were assigned by spectral data interpretation [280]. Phakellia pulcherrima from the Philippines contained the minor diterpene isothiocyanates kalihinol L (284), 10-isothiocyanatokalihinol G (285), 10-epi-kalihinol H (286) and 10-isothiocyanatokalihinol C (287) [281]. 10-Epi-kalihinol I (288) and 5,10-bisisothiocyanatokalihinol G (289) were isolated from an Acanthella sp. from Okinawa [282]. 

A Japanese sponge of the Adociidae family contained 10-isothiocyanatobiflora-4,15-diene (290), which was identified by spectral analysis [283], A. cavernosa from Fiji yielded a diterpene isothiocyanate (291) [284]. 

Cymbastela hooperi from the Great Barrier Reef contained four diterpene isothiocyanates (292-295) amongst other diterpenes [285]. An amphilectene isonitrile (296) was isolated from a Caribbean Cribochalina sp. [286]. 

Diterpene isothiocyanates fall into three distinct structural categories regarding their carbon skeletons the acyclic tetraenes (220 and 221), the biflorane framework (including the kalihinol family) (222-238), and the amphilectane framework (including the cyclo- and isocycloamphilectanes) (239-241). Like the sesquiterpene isothiocyanates, most of these compounds were isolated along with the corresponding isocyanate and formamide compounds. 

Table 3. Diterpene Isothiocyanates Belonging to the Kalihinol Family...

Koenig GM, Wright AD, Angerhofer CK. (1996) Novel potent antimalarial diterpene isocyanates, isothiocyanates, and isonitrile from tropical marine sponge Cymbastela hooperi. J Org Chem 61 3259-3267. 

The marine isothiocyanates, with more than 80 compounds isolated so far, form the largest group of naturally occurring isothiocyanates. This well-established group of marine natural products is constituted mainly by terpene metabolites present as sesquiterpene and diterpene derivatives. The non-terpene isothiocyanate compounds include two cylindricine alkaloids and a series of long-chain aliphatic metabolites. Marine sponges constitute the main source of these compounds, although they are also found in nudibranches and tunicates. 

Two acyclic diterpene tetraene isothiocyanates have been isolated from sponges so far. Famesyl isothiocyanate (220) was obtained from Pseudaxinyssa pitys [184] while compound (+)-221 was isolated from Halichondria sp. [185]. Their structures were elucidated by interpretation of their spectral data. 

Compounds 237 and 238 are the only isothiocyanate diterpenes with a biflorane carbon skeleton that do not belong to the kalihinol family. They are diastereosiomers of 10-isothiocyanatobiflora-4,15-diene. A planar structure was reported for compound 237, which was obtained from an unidentified sponge of the Family Adocidae [191]. A... 

Table 2 Isolation of Diterpene Isocyanides, Isothiocyanates, Formamides and Related Compounds 1976-1997...

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