Novel carbon skeleton

Brito I, Cueto M, Dorta E, Darias J (2002) Bromocyclococanol, a Halogenated Sesquiterpene with a Novel Carbon Skeleton from the Red Alga Laurencia obtusa. Tetrahedron Lett 43 2551... 

Liu, J.-Y Liu, C.-H. Zou, W.-X. Tan, R.-X. Leptosphaeric acid, a metaboUte with a novel carbon skeleton from Leptosphaeria Sp. Iv403, an endoph3dic fungus in Artemisia-annua. Helv. Chim. Acta, 2003, 86 657-660. 

Besides compounds 110 and 111, two new compounds (119, 120) representing a novel carbon skeleton having a new stilbene-coumarin nucleus, were isolated from the root bark of Ekebergia benguelensis. The structure of 119 was elucidated by 2D spectral methods and confirmed by single X-ray analysis [65]. 

During the last thirty-five years, a variety of biologically active substances bearing a novel carbon skeleton have been found in marine organisms. Of them, a number of highly brominated diphenyl ethers with antibacterial and antitumor activities were isolated from Dysidea herbaceae and Ptychodera flava laysanica. These metabolites are regarded as a self-defensive substance. In order to synthesize these metabolites, electrochemical oxidation of bromophenols has been carried out °. Some typical examples are shown here. 

Due to the immense effort already made in the discovery of isoprenoid natural products from macroalgae, uncovering novel carbon skeletons is now rare. However, several reports have recently been published on macroalgal isoprenoids that possess novel connectivities and cyclizations. 

Novel metabolites of mixed biogenesis are more likely to contain novel carbon skeletons than are the better-explored isoprenoid secondary metabolites. Therefore, hybrid metabolites from macroalgae seem to become front-runners for exciting natural product discovery. Uncovering novel skeletons for new scaffolds remains an integral part of drug discovery. 

The 5(R)- and 5(,S)-polyandranes (33 and 29), Zus-lactones, were isolated from Castela texana and Castela polyandra [17], respectively, and have been shown by single-crystal X-ray analysis to possess the novel carbon skeleton. In view of the structural similarity between the polyandranes and the C20 quassinoids, it has been suggested that (33) and (29) are derived biogenetically from chaparrinone (226) [134]. 

The discovery of a natural product with a novel carbon skeleton will undoubtedly challenge organic chemists to develop synthetic routes for its construction. If the natural product is complex, because of the presence of delicate functional groups and/or myriad chiral centers, the challenge becomes virtually irresistible. If the material displays biological activity, organic chemists will succumb to the challenge, and in time, a synthesis will be achieved. 

Cubitermes umbratus is an example of a termite using the second type defense. Soldiers produce four diterpenes, biflora-4,10 (19)-15-triene (156) (522), cembrane A (157) and 3-Z-cembrane A (158) (521) and cubitene (159). More recently, isolation and identification of cube-gene (160), a diterpene with a novel carbon skeleton from C. ugandensis soldiers, has been reported (539). Odontotermes badius also bites with... 

Tempesta, M.S., J.K. Pawlak, T. Iwashita, Y. Naya, K. Nakanishi, and G.D. Prestwick Cubegene, A Diterpenoid with a Novel Carbon Skeleton from a Termite Soldier (Isoptera Termitidae Termitinae). J. Org. Chem. 49, 2077-2079 (1984). 

Zhou CX, Liu JY, Ye WC, Liu CH, Tan RX (2003) Neoverataline A and B two antifimgal alkaloids with a novel carbon skeleton from Veratrum taliense. Tetrahedron 59 5743-5747... 

Ginkgolides (e.g., ginkgolide-B, 444), from the root-bark of Ginkgo biloba, have a novel carbon skeleton. Biosynthetic experiments have shown that their genesis apparently involves a seconor rearranged pimarane and C-methylation with methionine (293). 

Matsuo, A., H. Nozaki, M. Nabcayama, D. Tabcaoka, and S. Hayasia Structure of (— )-Neoverrucosane-5p-ol, a Diterpenoid from Mylia verrucosa (Liverwort) Containing a Novel Carbon Skeleton X-Ray Crystal and Molecular Structure of the Benzoate. Chem. Commun. 1980, 822. 

Recently, a novel carbon skeleton derived from cha-migrane has been characterized in gomerones A-C, three chlorinated cydohexenones isolated from the Spanish species Laurencia majuscula collected at La Gomera, Canary Islands (Diaz-Marrero et al., 2008). 

Diaz-Marrero, A.R., Brito, I., de la Rosa, J.M., Darias, J., and Cueto, M. (2008) Gomerones A-C, halogenated sesquiterpenoids with a novel carbon skeleton from Laurencia majuscula. Tetrahedron, 64, 10821-10824. 

Kikuchi, H., Suzuki, T., Kurosawa, E and Suzuki, M. (1991) The structure of notoryne, a halogenated Cjs nonterpenoid with a novel carbon skeleton from the red alga Laurencia nipponica Yamada. Bull. 

Rodriguez, A.D., Gonzalez, E., and Huang, S.P.D. (1998e) Unusual terpenes with novel carbon skeletons from the West Indian sea whip Pseudhrpterogor a elisabethae (Octocorallia). J. Org. Chem., 63, 7083-7091. 

Phuwapraisirisan, P., Matsunaga, S., Van Soest, R.W.M., and Fusetani, N. (2004) Shinsonefuran, a cytotoxic furanosesterterpene with a novel carbon skeleton, from the deep-sea sponge Stoeba extensa. Tetrahedron Lett., 45,2125—2128. 

Ageta, H., K. Masuda, M. Inoue, and T. Ishida Fern Constituents. Colysanoxide, an Onoceroid Having a Novel Carbon Skeleton, Isolated from Colysis species. Tetrahedron Letters 1982, 4349. 

Ito, S., K. Endo, T. Yoshida, M. Yotagai, and M. Kodama Chamigrene, a Sesquiterpene Hydrocarbon of a Novel Carbon Skeleton. Chem. Commun. 1967, 186. 

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