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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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Daria Polikarpova Daria Makeeva Nadezhda Kolotilina Anatoly Dolgonosov Maria Peshkova Liudmila Kartsova 《Electrophoresis》2020,41(12):1031-1038
The first example of application of nanosized polystyrene-based cation exchanger (NSCE) with sulfo groups as a dynamic coating of capillary walls was demonstrated. The conditions of dynamic coating formation were optimized and ensured the long-term stability of the coating. Capillary-to-capillary and day-to-day repeatabilities were 4% and 3%, correspondingly. The NSCE coating stability at various pH and influence of pH on the EOF mobility were investigated. The developed NSCE-modified coated capillaries provided improved resolution (Rs = 0.9–3.2 for catecholamines and Rs = 1.7–2.8 for amino acids) and efficiencies (330–520 ×103 t.p./m) of basic analytes, which are 1.5 times higher compared to untreated capillary. The optimized conditions were as follows: 50 mM phosphate buffer solution at pH 2.2 with 5 μM NSCE. The effect of the NSCE concentration in BGE on the electrophoretic mobilities of the analytes was investigated. The various online concentration techniques were tested in order to decrease the LODs. The simultaneous application of NSCE capillaries and field-amplified sample stacking provided the lowest LODs of catecholamines and amino acids and allowed to determine these analytes in human urine. 相似文献
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Anastasia E. Sleptsova Liudmila N. Alyabyeva Evgeny A. Gorbachev Ekaterina S. Kozlyakova Maxim A. Karpov Chen Xinming Alexander V. Vasiliev Boris P. Gorshunov Anatoly S. Prokhorov Pavel E. Kazin Lev A. Trusov 《Mendeleev Communications》2021,31(2):221-223
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9.
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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