Axinella

The first marine isocyano metabolite was appropriately named axisonitrile-1 (1) based on the trivial name isonitrile and the genus of the sponge, Axinella cannabina, which also furnished axisothiocyanate-1 (2) [1] and, subsequently, a minor constituent, axamide-1 (3) [5]. This observation that isonitriles are often accompanied by isothiocyanates (-N=C=S) and formamides (-NHCHO) was later duplicated by the Hawaiian researchers working with a Halichondria sp. In... 

Tetractinomorpha Axinellida Axinellidae Axinella Naples, Italy c15 [1]... 

Axisonitrile-1 (1) and axisothiocyanate-1 (2) were the first pair of NC/NCS compounds isolated from Axinella cannabina, see Introduction [1]. That both compounds possessed a new skeleton was evident, when 1 was reduced (Li/EtNH2) to axane (6). Other transformations involving the exocyclic methylene which survived selective reduction (Na/NH3) of 1, coupled with evaluation of the lHNMR data, supported its gross structure. Confirmation of 2 was secured when 1 was heated with sulfur and the resultant purified product found to be identical to the natural product. 

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. 

A minor isonitrile named acanthellin-2 with a specific rotation of — 24.1° was reported with no further details except some IR and MS data [3]. Isothiocyanate 15 and formamide 16 were also isolated from Axinella cannabina in a later study, in which isonitrile 14 and isomers 17-19 were also secured [35]. That 17-19 are C4(14)-ene isomers of 14 was concluded after extensive double resonance H NMR experiments. Coupling constants and nOe effects between the affected protons and various substituents of 17 established the relative stereochemistry of this series. 

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... 

The structures and relative stereochemistry of epi-eudesmanes 25-27 from Axinella cannabina were formulated from 2D NMR and chemical correlation experiments [36]. The 500 MHz HNMR spectrum of 1 l-formamido-7/ H-eudesm-5-ene (27) measured in CDC13 showed a 2 3 cis.trans ratio of the -NHCHO group (cis 3 8.06 d, J = 2 Hz trans 5 8.20 d, J — 12 Hz). Isothiocyanate 26 was one of several sesquiterpenes reported from Acanthella pulcherrima [20]. 

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. 

Continued studies by the Naples group of Axinella cannabina resulted in another epimaaliane series of isocyano-related compounds, 73-75. Dehydrogenation of 73 with Pd/C at 350 °C afforded eudalene (13). The cyclopropyl moiety was evidenced by both proton and carbon resonances in the NMR spectra and relative stereochemistry was assigned by coupling constants and nOe data [52],... 

Reef fishes Orange sponge Axinella sp. Indoles herbindole A Herb eta/., 1990... 

Herb, R., Carroll, R., Yoshida, W. Y., Scheuer, P. J., and Paul, V. J. (1990). Polyalkylated cyclopentindoles cytotoxic fish antifeedants from a sponge, Axinella sp. Tetrahedron 46, 3089-3092. 

Sesquiterpenoids based on the axane skeleton (354) have been reported previously as metabolites of marine sponges or algae (cf. Vol. 5, p. 77 Vol. 6, p. 89). Further investigations in this area have revealed the presence of axisonitrile-4 (355), axisothiocyanate (356), and axamide-4 (357) in the sponge Axinella cannabina. These compounds are A -derivatives of known metabolites (axisonitrile-1 etc.) of this sponge and are included in this section because their biosynthesis may involve rearrangement of a eudesmane precursor. 

Squalene-derived triterpenes, sodwanones and iccosodwanones, isolated from the axinellid sponge Axinella weltneri, may be added if Sodwana Bay, at the border between South Atlantic and the Indo-Pacific, is considered in the South Atlantic. 

Chart 7.9.1 Isc renoids (skeletons) from the South Atlantic (5 max=37, av=30 5///max=0.45, av=0.4). Triterp. soualaie derived sodwanmes and secosodwanones (Axinella weltneri, Axinel, Porif. from S Africa Rudi 1999B). 

A sesquiterpene isothiocyanate (240) was isolated from the Californian nudibranch Cadlina luteomarginata but was presumed to be concentrated from the Axinella species of sponge which constitutes much of its diet [249]. Famesyl isothiocyanate (241) was isolated from Pseudaxinyssa pitys [250], while theonellin isothiocyanate (242) was isolated from the sponge Theonella cf. swinhoei [251]. 

Axinellamines, e.g. axinellamine B (109), from the Australian marine sponge Axinella sp. with a unique heterocyclic skeleton have bactericidal activity against Helicobacter pylori, the bacterium associated with pepticular and gastric cancer, at 1 mM [88]. 

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