4586-65-6Relevant articles and documents
Preventive effect of taraxasteryl acetate from Inula britannica subsp. japonica on experimental hepatitis in vivo
Iijima,Kiyohara,Tanaka,Matsumoto,Cyong,Yamada
, p. 50 - 53 (2007/10/02)
The survival rate for acute hepatic failure induced by Propionibacterium acnes and lipopolysaccharide (LPS) was increased when a hot water extract from the flowers of Inula britannica h. subsp. japonica Kitam. was injected into the experimental hepatitis mice, and anti-hepatitis substances could be extracted with CHCl3. The CHCl3 extract from I. britannica was fractionated and anti-hepatitis fractions IB-3-2 and IB3-3 were obtained. IB-3-3 had the most potent antihepatitis activity among the fractions but further purification of the active compound was not achieved because of the low yield. IB-3-2 contained only one substance which was identified to be taraxasteryl acetate by 1H- and 13C-NMR and MS. Taraxasteryl acetate showed potent preventive activity against acute hepatic failure induced by P. acnes and LPS in a dose-dependent manner, however deacetylation and modification of the olefinic bonds significantly decreased the anti-hepatitis activity of taraxasteryl acetate. Taraxasteryl acetate also inhibited the increment of plasma transaminase on acute hepatic failure induced by carbon tetrachloride (CCl4) or D-galactosamine. From a histological study it appeared that degeneration and necrosis, which were observed in the liver from CCl4 mice, were not found in the liver cells from taraxasteryl acetate treated mice. These results indicates that taraxasteryl acetate shows preventive effects on experimental hepatitis caused by either immunologically induced injuries or hepatotoxic chemicals.
Wagner-Meerwein Rearrangements in Taraxasterol and Pseudotaraxasterol
Anjaneyulu, A. S. R.,Anjaneyulu, V.,Prasad, K. Harishandra,Rao, G. Sambasiva,Suryanarayana, P.
, p. 1179 - 1183 (2007/10/02)
Both taraxasterol (I) and pseudotaraxasterol (II) give A-nor-3,4-dichloro products (IV) and (VI) respectivly when heated with PCl5 in n-hexane.With POCl3 in pyridine I and II give the same product (VII) without contraction of ring-A while solvolysis of their respective tosylates (X and XII) gives a different, but identical product (XI) from both, attended by contraction of ring-A.Both the tosylates (X and XII) are found to undergo, detosylation when passed through a column of silica gel giving VII and V respectively.The Wagner-Meerwein rearrangements noticed in thesetwo compounds have been rationalised mechanistically.
Steric Effects on Oxymercuration: Oxymercuration-Demercuration of Taraxasteryl, Pseudo-Taraxasteryl, and 19-Epi-Taraxasteryl Acetates
Majumder, P. L.,Laha, S.
, p. 548 - 554 (2007/10/02)
Contrary to usual expectation, taraxasteryl acetate (1b) and pseudo-taraxasteryl acetate (2b) were found to be totally intensive to normal oxymercuration.This has been rationalised as being due to the steric effects of the 19-and 17 methyl groups on the formation of intermediate mercurium ions, and on the nucleophile attacking these species.Conformational analysis of 1b shows that its ring E is not a normal chair, but assumes a twisted conformation due to severe nonbonded interaction between the 12-methylene and the 19-methyl group.Both 1b and 2b, however, underwent oxymercuration-demercuration with allylic rearrangement to give the same compound 2c, when heated with Hg(OAC)2 in glacial HOAc.A partial synthesis of 19-epi-taraxasteryl acetate (1d) has been achieved by Wittig reaction on the 19-epi-norketone (4b) formed by base-catalysed epimerization of 4a which in turn was derived from 1b.The steric effects providing the driving force for this unconventional epimerisation of 4a to 4b have been explained and supported by comparative 13C nmr spectral analysis of 4a and 4b.Unlike 1b and 2b, 19-epi-taraxasteryl acetate (1d) undervent normal oxymercuration.The stereochemical aspect of this reaction has been discussed.
