Cembrane diterpenoids

R. Enzell, J. Berg, and A. Pilotti. Tobacco chemistry. New cembranic diterpenoids from Greek tobacco. Acta Chem Scand Ser B 1980 34 195-202. NT547 Uegaki, R., T. Fujimori, H. Kaneko, K. 

A large number of cembrane diterpenoids have been obtained from marine organisms, particularly soft corals. 2-Hydroxynephthenol (116) was isolated from Litophyton viridis. A dehydro-derivative (117) of epoxynephthenol was... 

The oxidation of various cembrane diterpenoids by chromium trioxide has been noted. The full paper on the X-ray analysis of ovatodiolide and ovatodiolic acid has appeared. Detailed n.m.r. studies have led to the structures (124)—(127)... 

Characteristic to some important cembrane diterpenoids, such as isocembrene, cembrene, cembrene C, and sarcophytol A, is a 1,3-diene unit in the macrocyclic skeleton. In continuation of our ongoing project on the total synthesis of cembrane-type diterpenoids, we intended to explore a novel macrocyclization method to... 

Tobagolide 72, another novel cembrane diterpenoid containing a dimethylamino moiety, was isolated by Tinto and Chan and coworkers [49,50]. As shown in scheme 5, an unusual reaction of 72 under acetylation conditions led to the replacement of the dimethylamino moiety... 

Vicinal /hh couplings have been extensively applied by many authors in structural and stereochemical studies of natural products. Thus, they have been used by Guo and co-workers to establish the structure of four new ot-methylene-y-lactone-bearing cembrane diterpenoids from Lobophytum crassum. Further examples include two new sesquiterpenes isolated from Cyperus rotundus L. by Xu et three new eudesmanohdes, ten sesquiterpenes extracted from Inula helenium, by Ma et two lactone... 

Cheng, Y.-B., Shen, Y.-C., Kuo, Y.-H., and Khalil, A.T. (2008a) Cembrane diterpenoids from the Taiwanese soft coral Sarcophyton stolidotum. J. Nat. Prod., 71,1141-1145. 

Zhang, W., Krohn, X, Ding, J., Miao, Z.-H., Zhou, X-H., Chen, S.-H., Pesticelli, G., Salvadori, P Kiutan, T., and Guo, Y.-W (2008) Structural and stereochemical studies of a a-methylene-y-lactone-bearing cembrane diterpenoids from a South China sea soft coral Lobophytum crassum. J. Nat. Prod., 71,961-966. 

Frankincense, also called olibanum, is a natural oleo gum resin that exudes from incisions in the bark of Boswellia trees [46, 47]. Diterpenes like incensole or isoincensole and their oxide or acetate derivatives (see Figure 10.3) are characteristic biomarkers of olibanum [48]. Although diterpenoid hydrocarbons possessing the cembrane skeleton have been isolated from a variety of terrestrial and marine organisms, their occurrence and particularly that of cembrenes A and C (see Figure 10.3) is supplementary proof of the presence of olibanum in a sample. Optimisation of the SPME conditions was done with the aim of trapping these low volatile diterpenes. 

Wahlberg. Tobacco chemistry. 4,6,8-Trihydroxy-11-capnosene-2,10-dione, a new cembrane-derived bicyclic diterpenoid from tobacco. Acta Chem... 

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). 

STUDIES ON NOVEL MACROCYCLIZATION METHODS OF CEMBRANE-TYPE DITERPENOIDS... 

Thus, an efficient and convergent total synthesis of ( )-isocembrene has been accomplished in seven steps from the known geranylacetone through an intramolecular Stille cross-coupling reaction. The strategy is of great potential for the divergent synthesis of complex cembrane-type diterpenoids such as cembrene-C and sarcophytols. 

Extracts of Pseudopterogorgia acerosa produced a family of diterpenoids derived from the pseudopterane skeleton 62 [5]. Other complex secondary metabolites produced by P. acerosa include cembranes, polyhydroxy steroids and carotenoids. 

Iguchi, K., Shimura, H., and Yamada, Y. (1992b) New cembrane-type diterpenoids from the Okinawan soft coral Sinidaria sp. J. Nat. Prod., 55, 1779-1782. 

Shin, J. and Fenical, W. (1991b) New diterpenoids from the Caribbean gorgonian Eunica calyculata. Photochemical interconversion of the cembrane and cubitene skeletons./. Org. Chem., 56,1227-1233. 

Wen, T, Ding, Y, Deng, Z., van Ofwegen, L., Proksch, P., and Lin, W. (2008) Sinulaflexiolides A-K, cembrane-type diterpenoids from the Chinese soft coral Sinularia Jlexibilis.J. Nat. Prod., 71,1133-1140. 

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