Volubilide

These processes are normally enzyme-catalyzed. Purefy ctemical processes are seldom encountered with carbon conq)ounds in nature. The few exceptions include the very act of phenol coupling (by which racemic compounds are obtained), cyclization reactions ofpolyprenyl compoimds (which benefit from the preferred conformation of the reaction partners, suitable for the cyclization, Wendt 2000), and Diels-Alder cycloadditions. The latter have been advocated for the biosynthesis of celastroidine A (= volubilide) from a lupane triterpene and an abietane diterpene in two different plants, Hippocratea celastroides Kunth from Mexico (Jimenez-Estrada 2000) and Hippocratea volubilis Linnaeus (Alvarenga 2000). 

Alvarenga, N.L. Ferro, E.A. Ravelo, A.G. Kennedy, M.L. Maestro, M.A. Gonzalez, A.G. (2000) X-Ray analysis of volubilide, a new decacyclie Diels-AldCT C20-C30 adduct from Hyppocratea volubilis L. Tetrahedron, 56, 3771-4. 

From the root bark of H. volubilis, volubilide (51) was isolated. This unusual compound has a structure based on two monomer units from abietane and lupane di/triterpene skeletons. From its HREIMS, H, 13C-NMR and X-ray data the molecular formula C50H74O5 was obtained for (51). From the l3C-NMR data and 2D NMR experiments, the C-30 unit was identified as a lupane derivative with a 30-21a lactone group, related to ochraceolide A [65]. 

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