Clavularia

Clavulones I and II are members of an unusual family of marine prostanoids from the coral Clavularia viridis which are biosynthesiied by a cationic (i.e. non-radical, non-endoperoxide) pathway. The total synthesis of clavulones I and II was accomplished from cyclopentadiene as SM goal. 

Extracts from Clavularia viridis and also many other coral species convert arachidonic acid to the prostanoidpreclavulone-A via 8-( f )-hydroperoxy-5,ll,14( Z), QfEj-eicosatetraenoic acid. The carbocyclization is considered to occur from allene oxide and oxidopentadienyl cation intermediates. An enantioselective total synthesis of preclavulone-A was developed to assist the biosynthetic research. 

An unusual combination, namely a Michael addition and a Simmons-Smith reaction, has been elaborated by the group of Alexakis [112]. Using their protocol, 3/5-as well as 3/6-annulated systems can easily be obtained, which might be useful as precursors for the total syntheses of (-)-(S,S)-clavukerin A and (+)-(R,S)-iso-clavukerin, both isolated from Clavularia koellikeri [113]. 

Ai HW, Henderson JN, Remington SJ, Campbell RE (2006) Directed evolution of a monomeric, bright and photostable version of Clavularia cyan fluorescent protein structural characterization and applications in fluorescence imaging. Biochem J 400 531-540... 

Ai HW, Olenych SG, Wong P, Davidson MW, Campbell RE (2008) Hue-shifted monomeric variants of Clavularia cyan fluorescent protein identification of the molecular determinants of color and applications in fluorescence imaging. BMC Biol 6 13. doi 10.1186/1741-2007-1186-1113... 

Scheme 10. Proposed biosynthesis of clavulone I (88) in Clavularia viridis [85]...

Shick, J.M., M.P. Lesser, and W.R. Stochaj. 1991. Ultraviolet radiation and photooxidative stress in zooxan-thellate anthozoa the sea anemone Phyllodiscus semoni and the octocoral Clavularia sp. Symbiosis 10 145-173. 

The structure and relative configuration of six new dolabellanes (30-35) isolated from the soft coral Clavularia inflata collected at Orchid Island located 44 nautical miles off Taiwan s southeast coast is depicted in Fig. 4 [16]. The relative configuration was assigned based on ID and 2D NMR spectroscopy and supports the cis arrangement between the isopropyl group at... 

Fig. 4 Six dolabellanes (30-35) isolated from the soft coral Clavularia inflata (2001)...

Iwashima, M. Okamoto, K. Miyai, Y. Iguchi, K. (1999) 4-Epiclavulones, new marine prostanoids fixm the Okinawan soft coral, Clavularia viridis. Chem. Phaim. Bull., 47, 884-6. 

New diterpenoids of the dolabellane class have been reported, such as clavinflol B (592) from the Taiwanese soft coral Clavularia inflata (706). This metabolite has comparable cytotoxicity against the KB cell line to doxorubicin. A sea whip of the genus Eunicea has yielded the cembrane 593 (707). Both 592 and 593 are considered to be natural since no chlorinated solvents were used in the isolation process, and in both metabolites the chlorine is attached to the less substituted carbon, opposite to what is expected for acid-induced epoxide ring opening. A Kenyan soft coral, Sinu-laria erecta, contains the norcembrane sinularectin (594) (708). 

A practical racemic synthesis of the known chlorovulone II from the Okinawan soft coral Clavularia viridis has been accomplished (922). This coral has more recently afforded the new prostanoids 852-856 (923), 857-871 (924), and, from a Taiwanese collection, 872, 873 in addition to 857 and 858 (925). The absolute configuration of the previously known punaglandin 8 (852, X = Cl) was determined as shown (923). This soft coral also contains several non-halogenated possible biosynthetic precursors to these halogenated metabolites (926). 

Shen Y-C, Pan Y-L, Ko C-L, Kuo Y-H, Chen C-Y (2003) New Dolabellanes from the Taiwanese Soft Coral Clavularia inflata. J Chin Chem Soc 50 471... 

Iwashima M, Nara K, Nakamichi Y, Iguchi K (2001) Three New Chlorinated Marine Steroids, Yonarasterols G, H and I, Isolated from the Okinawan Soft Coral, Clavularia viridis. Steroids 66 25... 

Watanabe K, Sekine M, Takahashi H, Iguchi K (2001) New Halogenated Marine Prostaglandins with Cytotoxic Activity from the Okinawan Soft Coral Clavularia viridis. J Nat Prod 64 1421... 

Shen Y-C, Cheng Y-B, Lin Y-C, Guh J-H, Teng C-M, Ko C-L (2004) New Prostanoids with Cytotoxic Activity from Taiwanese Octocoral Clavularia viridis. J Nat Prod 67 542... 

McClintock, J. B., Baker, B. J., Slattery, M., Heine, J. N., Bryan, P. J., Yoshida, W., Davies-Coleman, M. T., and Faulkner, D. J., Chemical defense of common Antarctic shallow-water nudibranch Tri-toniella belli Eliot (Molluscs Tritonidae) and its prey Clavularia frankliniana Rouel (Cnidaria Octocorallia), J. Chem. Ecol., 20, 3361, 1994. 

Iwashima, M., Watanabe, K., and Iguche, K., New marine prostanoids, preclavulone lactones, from the Okinawan soft coral Clavularia viridis, Tetrahedron Lett., 38, 8319, 1997. 

Bathydoris hodgsoni can be found in the deep waters of the Weddell Sea. This nudibranch elaborates the drimane sesquiterpene hodgsonal (Structure 7.78) and sequesters it in its mantle tissues.50 164The nudibranch Tritoniella belli collected from McMurdo Sound is the only documented example of an Antarctic mollusc sequestering defensive chemistry from its diet.44 Among the glyceride esters (Structures 7.79-7.81) isolated from this species, chimyl alcohol (Structure 7.79) can also be found in one of its prey items, the stoloniferan coral Clavularia frankliniana. Sequestration of these defensive chemicals is opportunistic, however, and other, still undescribed metabolites are more commonly associated with defense in this mollusc.49... 

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