Acanthella acuta

About two dozen isocyano- and isocyano-related compounds with a eudesmane (12) skeleton are known. Although most of these were isolated from Axinella cannabina, the first isocyanoeudesmane, acanthellin-1 (14) [3], was obtained from a related sponge, Acanthella acuta, (cf. Table 2). Eudalene (13) resulting after two steps (i. Li/EtNH2, . Pd/C) from 14, proved the eudesmane skeleton. 

Compounds 20-22 are further examples of minor metabolites of Axinella cannabina [40]. When Acanthella acuta was reinvestigated by the same researchers, isocyano compound 20, but not acanthellin-1 (14), was found to be the... 

Fattorusso s group, which earlier had discovered 48-50 in Axinella cannabina, reported the occurrence of another spiroaxane series, 51 and 52, from Acanthella acuta. The habitat of the latter sponge is the Bay of Naples. As was the case with other metabolites reported in their recent studies, the investigators deduced the structures of isonitrile 51 and iso thiocyanate 52 chiefly by 2D NMR methods. 

An isocyano- and isothiocyano pair of sesquiterpenes, 125 and 126, is included in this section. Upon reexamination of Acanthella acuta, both 125 and 126 were discovered as part of the nitrogenous sesquiterpenes in the sponge [41], The relative configuration of the sesquiterpene compounds was deduced from extensive 2D NMR experiments and shown to be similar, and, perhaps, biogenetically related, to the aphanamols (127) [41],... 

Attributed to seasonal variations was the noted absence of isocyano-related metabolites in one batch of C. luteomarginata [18]. Similarly, in previous studies on Acanthella acuta, aeanthellin-1 (14) was the major constituent of the isonitrile fraction [3], but a subsequent reinvestigation by a different group showed that 14 was only a minor constituent [32],... 

Compounds containing the isocyano group have fascinated natural products chemists ever since the first isocyanide xanthocillin was isolated from the fungus Penicillium notatum Westling in 1950 [1]. The existence of sesquiterpene isocyanides was first reported from the Mediterranean sponge Axinella cannabina in 1973 [2], closely followed by sesquiterpene isocyanides from the Mediterranean sponge Acanthella acuta by Minale et al. [3] and the Hawaiian sponge Halichondria sp. by Scheuer et al. [4]. These early reports also documented the presence of isothiocyanate [2] and formamide [4] functionality attached to the same carbon nucleus as the... 

SPECTRAL data IR, PMR, Mass Spec ORGANISM Acanthella acuta (Platyhelminthes) reference 296... 

Ciminiello, P., Magno, S., Mayol, L., and Picdalli, V. (1987a) ds-Eudesmane nitrogenous metabolites from marine sponges AxineUa cannabina and Acanthella acuta. J. Nat. Prod., 50, 217-220. 

Mayol, L Picciali, V and Sica, D, (1987a) Nitrogenous sesquiterpenes from the marine sponge Acanthella acuta three new isocyanide-isothiocyanate pairs. Tetrahedron. 43, 5381-5388,... 

The third sesquiterpene isonitrile in Chart 5 has been isolated from the extracts of Acanthella acuta, which also yielded a number of minor compounds 138). The major component, acanthellin-1, proved to have a 4-epi-eudesmane structure (49). The carbon skeleton was deduced by lithium/ethylamine reduction, which afforded a saturated bycyclic hydrocarbon (60) converted into eudalene by drastic dehydrogenation. The i.r. 

Minale, L., R. Riccio, and G. Sodano Acanthellin-1, a unique isonitrile sesquiterpene from the sponge Acanthella acuta. Tetrahedron 30, 1341 (1974). 

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