Marine natural products. Xenicin: a diterpenoid possessing a nine-membered ring from the soft coral, Xenia elongata

13-Epi-9-deacetoxyxenicin, a Cytotoxic Diterpene from the Soft Coral Asterospicularia laurae (Alcyonacea)

“…It should be noted that single crystal x-ray structures of xenicane diterpenes like xenicin [3], indicate that the Δ 7,8 bond lies orthogonal to the ring junction. This would be expected to prevent approach for endo addition to the olefinic bond.…”

Some structures of marine natural products

“….6475(8) .0728 (36) .4415(7) C (15) .7761(8) .0035 (45) .2103(6) 0 (16) .8667(6) -.2312 (32) .2603(6) 0 (17) .8029(5) -.0064 (35) .1439(4) C (18) .7510(9) .0079 (45) .0833(6) 0 (19) .6821(5) .0198 (38) .0829(5) C (20) .7819(8) .0006 (41) .0146(6) C (21) .8586(9) -.0361 (39) .0155(7) C (22) .8848(7) -.0318(38) -.0484(8) C (23) .8412(9) .0015(47) -.1147(7) C (24) .7586(9) .0393(34) -.1168(6) C (25) .7335(8) .0357(36) -.0532(8) Br (26) .8736(1) -.0038(29) -.2018(1) C (27) .9874(9) .5412 (38) .1507(8) C (28) 1.0520(8) .5114 (52) .2099(8) C (29) .9850 (15) .3745 (66) .0950(16) 0 (30) .9400(7) .6580 (35) .1442(6) Table 9c. Bond angles of sinularene.…”

A new xenicane norditerpene from the Indian marine gorgonianAcanthogorgia turgida

“…Xenicanes, which are diterpenes based on a xeniane skeleton (Vanderah et al, 1977), are typical secondary metabolites of marine octocorals of the orders Alcyonacea (soft corals) and Gorgonacea (gorgonians). After the isolation of xenicin (Vanderah et al, 1977), the first member of this class of diterpenoids, several related compounds have been found in soft coral species belonging to different genera (such as Xenia, Alcyonum, Cespitularia) (Andrianasolo et al, 2007;Bishara, Rudi, Goldberg, Benayahu, & Kashman, 2006;Blunt et al, 2007;Duh, Li, Wang, & Dai, 2006), as well as in gorgonians of genus Acalycigorgia and Paragorgia (Blunt et al, 2007;Rho, Oh, Jang, Cho, & Shin, 2001).…”

“…After the isolation of xenicin (Vanderah et al, 1977), the first member of this class of diterpenoids, several related compounds have been found in soft coral species belonging to different genera (such as Xenia, Alcyonum, Cespitularia) (Andrianasolo et al, 2007;Bishara, Rudi, Goldberg, Benayahu, & Kashman, 2006;Blunt et al, 2007;Duh, Li, Wang, & Dai, 2006), as well as in gorgonians of genus Acalycigorgia and Paragorgia (Blunt et al, 2007;Rho, Oh, Jang, Cho, & Shin, 2001). Distinct framework types can be recognised among xenicanes, which include xenicins (Vanderah et al, 1977), xeniolides (Kashman & Groweiss, 1978), xeniaphyllanes (Kashman & Groweiss, 1980), xeniaethers (Iwagawa, Amano, Nakatani, Hase, & Shiro, 1995), and azamilides (Iwagawa, Amano, Nakatani, & Hase, 1996), all of which display a ninemembered ring and differ in the presence of additional fused cycles. Most of the xenicane diterpenes have been reported to be significantly cytotoxic against a number of human cancer cell lines (Ciavatta et al, 2006;Manzo et al, 2007;Wahidullah, Guo, Fakhr, & Mollo, 2006).…”