Celastroids

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). 

Jimenez-Estrada, M. Reyes-Chilpa, R. Hemandez-Ortega, S. Cristobal-Telesforo, E. Torres-Colfn, L. Jankowski, C.K. Aumelas, A. Van Calster, M.R. (2000) Two novel Diels-Alda adducts from Hippocratea celastroides roots and their insecticidal activity. Can. J. Chem., 78, 248-54. 

Although two novel celastroidines were isolated from the roots of Hippocratea celastroides (Celastraceae), only celastroidine A (357) strongly inhibited feeding by Sitophillus zeamais. Celastroidine A (357) is described as Diels—Alder adduct of a triterpene on a diterpene. It was isolated as a white powder.154... 

The aerial parts of Melodinus celastroides (Apocynaceae), as well as yielding several monoterpene indole alkaloids, including tabersonine (110),... 

The structure of 16BH-A -vincanol, a constituent of Melodinus celastroides, has been confirmed by X-ray crystal structure... 

Rabaron and Plat (295) have reported the isolation and structure elucidation of four new alkaloids from the leaves and twigs of Melodinus celastroides Baillon. 

Sarpagine-Ajmaline-Picraline-Vobasine Group. The roots and stems of Rauwolfia schueli Speg. (R. boliviana Mgf.) have been re-examined,and the ajmaline content has been quantitatively estimated the conclusion is that this plant constitutes one of the richest sources of ajmaline. Ajmaline also occurs in Melodinus balansae Baillon var. paucivenosus, normacusine B occurs in Strych-nos nux vomicai akuammidine in M. celastroides, and pericyclivine and caberine in the aerial parts of Catharanthus ovalis. ... 

The branches and leaves of Melodinus celastroides have yielded 19-epi-vindolinine, (19/ )- and (19S)-hydroxytabersomne, (-)-tabersonine, (-)-venalstonine, (-)-vindolinine, and five new alkaloids, which are 14,15-dehydroisoeburnamine, buxomeline (189), and three alkaloids whose structures have not yet been disclosed, viz. melonine, melonine TVb-oxide, and methylene-bis-l,r-melonine. The structure (189) of buxomeline was deduced almost entirely from its spectroscopic properties the presence of both Nb-carbinolamine and carbinolamine ether functions is unusual. 

Methylene-bis-l,l -melonine is a new constituent of Melodinus celastroides whose structure has not yet been revealed. ... 

CjsHseOj, Mr 420.59, yellow powder, mp. 78-80°C, [a] 5 -130° (CHCI3). An orange-yellow pigment from the lipophilic outer layer of the agaric Russula flavida in which it is accompanied by a dihydro derivative. The pigments have the same quinonemethide system (p-quinonemethane chromophore) as pentacyclic triterpenoids of the pristimerin type (celastroids). 

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