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The circular dichroism method has been used to establish the stereochemical features of the structure of the withasteroids. The 22S-configuration of the asymmetric center has been confirmed for physangulide. The 22R-configuration has been confirmed for 14-hydroxyixocarpanolide, vamonolide, ixocarpanolide, 24,25-epoxywithanolide D, and withanolide T. On the basis of changes in the circular dichroism spectra in acid and alkaline media it is suggested that in compounds having a 4-hydroxy-1-oxo-5,6-epoxy-2,3-ene grouping the 2,3 bond disappears, while in compounds having a 5-hydroxy-1-oxo-6,7-epoxy-2,3-ene grouping dehydration takes place at C-4-C-5. These characteristics can be used in the identification of the withasteroids. The isolation of withanolide T from the leaves ofPhysalis angulata L. is described and its spectral characteristics are given.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–376, May–June, 1990. 相似文献
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A new withasteroid — physangulide — has been isolated from the leaves ofPhysalis angulata L. It has been shown that physangulide is the first natural 22S-withanolide. Its structure has been determined as 3,4,20,24,25-pentahydroxy-1-oxo-5,6-epoxy-20R,22S,24S,25R-withanolide. Its1H and13C NMR spectra, confirming this interpretation, are given.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 366–371, May–June, 1990. 相似文献
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The circular dichroism method has been used to establish the stereochemical features of the structure of the withasteroids.
The 22S-configuration of the asymmetric center has been confirmed for physangulide. The 22R-configuration has been confirmed
for 14α-hydroxyixocarpanolide, vamonolide, ixocarpanolide, 24,25-epoxywithanolide D, and withanolide T. On the basis of changes
in the circular dichroism spectra in acid and alkaline media it is suggested that in compounds having a 4β-hydroxy-1-oxo-5β,6β-epoxy-2,3-ene
grouping the Δ2,3 bond disappears, while in compounds having a 5α-hydroxy-1-oxo-6α,7α-epoxy-2,3-ene grouping dehydration takes place at C-4-C-5.
These characteristics can be used in the identification of the withasteroids. The isolation of withanolide T from the leaves
ofPhysalis angulata L. is described and its spectral characteristics are given.
Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh
Soedinenii, No. 3, pp. 371–376, May–June, 1990. 相似文献
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T. V. Vasina L. M. Kustov I. A. Novakov B. S. Orlinson 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(1):20-22
We study the effect of adamantane-containing additives on the process of isomerization of n-heptane in the ionic liquid trimethylammonium hydrochloride-aluminum chloride (1 : 2 mol). It is shown that introducing 1-cyanomethyl-3-cyanoadamantane (5.0 wt %) into the reaction mixture slows conversion and lowers the yield of iso-products by a factor of more than 1.5, while adding adamantylpolyimide (0.5–5.0 wt %) substantially accelerates the isomerization of n-heptane and increases the yield of iso-products. In addition, this reaction proceeds under mild conditions at 40°C in the absence of hydrogen and precious metals. 相似文献
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提出了强拟Armendariz环的概念,给出了强Armendariz环和强拟Armendariz环上的一些结果. 相似文献
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