Eunicellanes

Mancini, I. Guella, G. Zibrowius, H. Laurent, D. Pietra, F. (1999A) A novel type of second epoxy bridge in eunicellane diterpenes isolation and characterization of massileunicellins A-C from the gorgonian Etmicella cavolinii. Helv. Chim. Acta, 82, 1681-9. 

Other soft coral metabolites reported to show antifeedant effects against fish include heterogorgiolide 119 and the eunicellane 120 from Heterogorgia uatumani,iv> and furanocembrenoid diterpenes, for example, 1 3-acetoxy-11 ft, 12/3-epoxypukalide 121, from Lophogorgia violacea.150... 

Overman et al. were the first to synthesize the eunicellane carbon skeleton [20]. In contrast to eleutherobin (1), (-)-7-deacetoxyalcyonin acetate (45) from the marine soft coral Cladiella sp. [21] shows the oxygen bridge between C2 and C9 instead of C4 and C7. Starting from 5(+)-carvone, an elegant Prins-pinacol conden-... 

In conclusion, three independent syntheses of marine eunicellane diterpenoids have been developed, which will be the basis of the future development of this exciting natural product class. The biosynthesis of the eunicellanes probably involves the oxidative cyclization of a cembranoid precursor lacking solely the bond between Cl and CIO (C, Fig. 3). Considering the number of carbon - carbon bonds formed in the course of... 

Lathyrane formally cyclizes to tigliane by closing the C-5-C-14-bond which, on its part, converts into rhamnofolane and daphnane by opening the 2,15- and the 1,15-bond, respectively (Table 4). Eunicellanes represent 2,5-cyclocembranes, which formally undergo C-18-methyl shift from C-4- to C-3 resulting in the formation of asbestinanes. Briaranes are 3,8-cyclocembranes (Table 4). 

Eunicellanes and (infrequently) asbestinanes are diterpenes of marine origin, including eunicelline from the alga Eunicella stricta and cladielline found in some Cladiella species. Asbestinanes such as (-)-asbestinine 2 are characteristic of the gorgonia Briareum asbestinum (Araceae). 

Mancini, I., Guella, G., Zibrowius, G., and Pietra, F. (2000) Configuration, conformation, and reactivity of highly functionalized eunicellane diterpenes isolated from the gorgonians Eunicella cavolini and Eunicella singularis, Helv, Chim, Acta, 83,1561-1575. 

Roussis, V Fenical, W Vagias, C., Komprobst, J.M., and Mrralles, J. (1996) Labiatamides A, B, and other eunicellan diterpenoids from the Senegalese gorgonian Eunicdla labiata. Tetrahedron, 52, 2735-3742. 

CladieUane differs from eunicellane by the absence of the ether bridge between carbons 2 and 9 that is present in the eunicellane skeleton, which is also much more common than dadiellane. The junctions of the two carbon rings and the junction of the ether bridge within the cyclodecane are generally as. The presence of a second ether bridge between carbons 3 and 7, as well as that of a single bridge at 2,6 has been reported (see below). 

Among the biological activities of derivatives of briarane, dadiellane and eunicellane, it is worth mentioning antifouling and insecticidal properties, as well as cytotoxic, antiviral and anti-inflammatory activities, and it has been shown recently that some ermiceUane derivatives have antimalarial activity (see below Ospina et al., 2003). 

Briarane Cladiellane Eunicellane Serrulatane Dolabellane Neodolabellane... 

Nitrogen-Containing Diterpenes ofCladidlane/ Eunicellane Eleutherobin and Analogs,... 

Noticeably less frequently represented than the briarane skeleton, the skeleton of cladiellane/eunicellane is mainly present in the Alcyonacea, in the order Alcyoniidae. Some examples have been found in Gorgonacea Eunicdla in particular), but among other orders of Octocorallia it seems that only the genus Sarcodictyon (Stolonifera) has yielded any of these compounds (Table 20.12). As with most previous diterpenes, the presence of a yl ctone... 

Figure 20.52 (a) Examples of cladiellane/eunicellane derivatives isolated from Alcyonacea (b) Examples of cladiellane/eunicellane derivatives... 

Figure 20.53 Examples of cladiellane/eunicellane derivatives isolated from Gorgonacea.

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