Triterpenoids isomerization

Gowri, P. M, Radhakiishnan, S. V, Basha, S. J, Sarma, A. V, Rao, J. M. Oleanane-t)rpe isomeric triterpenoids from Barringtonia racemosa. Journal Natural Product. (2009). 

Rearrangements of nonconjugated alkenes have also been observed. Thus, a triterpenoid (partial structure 38) afforded the alkene (39 32% yield) upon reduction (Barton modification), a result attributed to initial base-induced isomerization of (38) to the corresponding a,3-unsaturated ketone followed by rearrangement during reduction. ... 

A new method for the degradation of the typical iso-octenyl side-chain of tetracyclic triterpenoids has been reported. The key step involves N-lithioethylene-diamine-induced double-bond isomerizations of the olefin (50), obtained by lead tetra-acetate decarboxylation of the trisnoracid (51), to a mixture of (52) and (53). The details of the n.m.r. spectra of 45 cycloartane derivatives have been described and assignments made for the methyl group signals. "... 

Dehydration of epoxides. When the triterpenoid epoxide (1), or the isomeric < -oxide, is refluxed with pyridine hydrochloride in pyridine it is converted in high yield into the diene (2). Use of hydrochloric acid in ethanol is attended with re-... 

Martelanc, M., Vovk, I., and Simonovska, B. 2009. Separation and identification of some common isomeric plant triterpenoids by thin-layer chromatography and high performance liquid chromatography, J. Chromatogr. A, 1216 6662-6670. 

Shiengthong, D., U. Kokpol, P. Karntiang, and R. A. Massey-Westropp Triterpenoid Constituents of Thai medicinal plants — II. Isomeric Aglaitriols and Aglaiondiol. Tetrahedron 30, 2211 (1974). 

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