Results 181 to 190 of about 21,587 (210)
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Epimerization of 6-bromoprogesterone
Steroids, 1986Epimerization of 6-bromoprogesterone is observed by 1H NMR. The equilibrium constant K = 1.5 and the standard free-energy delta G = -241 cal/mol at 302 K.
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Thermal epimerization of diastereomeric Grignard reagents
Org. Biomol. Chem., 2009Thermal epimerization is the key to changing the endo-to-exo ratio of the diastereomeric bornyl and fenchyl Grignard reagents from 67:33 to 96:4 and from 20:80 to 80:20, respectively.
Jens, Beckmann, Alexandra, Schütrumpf
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THE EPIMERIZATION OF DELCOSINE
Canadian Journal of Chemistry, 1961Delcosine has been assigned tentatively the same C—N skeleton as lycoctonine. In lycoctonine, ring A carries at C-1 a methoxyl group which is directed away from the nitrogen ring. In delcosine, C-1 carries a hydroxyl group which has the opposite configuration and is directed towards the nitrogen.
Vinko Skarić, Léo Marion
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Epimerization of isotactic polystyrene
Polymer Bulletin, 1979A procedure for epimerizing isotactic polystyrene and a Monte-Carlo computer program for simulating polymer epimerization reactions have been developed. The 300 MHz methine proton resonance patterns of partially epimerized isotactic polystyrene and of free radical initiated polystyrene have been analyzed.
Lloyd Shepherd +2 more
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Tetracycline Epimerization Kinetics Utilizing NMR Spectrometry
Journal of Pharmaceutical Sciences, 1973NMR was used to monitor the epimerization of tetracycline since the dimethylamino resonance of tetracycline and its C-4 epimer differ by 0.1 p.p.m. This method eliminated the need for acidification in the previously reported spectrophotometric method, thereby lessening the possibility of anhydro formation which occurs in the presence of mineral acids ...
K D, Schlecht, C W, Frank
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Epimerization of Cypermethrin Stereoisomers in Alcohols
Journal of Agricultural and Food Chemistry, 2009Isomerization induced by light, heat, and organic solvents has been shown to occur for some pyrethroid insecticides. Alcohols are popular solvents that are used in sample extraction, storage, and analysis. Thus, alcohol-induced epimerization may contribute to the incorrect interpretation of results from enantioselective chemical analysis and bioassay ...
Mae Grace, Nillos +4 more
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The Epimerization of Sesamin and Asarinin
Journal of Natural Products, 2005Sesamin (1) and asarinin (2) are two C-7' epimeric lignans. Molecular modeling by semiempirical methods indicated that 1 is more stable than 2 by about 2.5 kcal/mol. However, epimerization under acidic conditions led to a 44.8/55.2 equilibrium ratio of 1 and 2.
Chia-Ying, Li +2 more
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Chromatographic properties of the epimeric estriols
Journal of Chromatography A, 1971Abstract Thin-layer and gas chromatographic methods to separate the epimeric estriols are described. Gas chromatography of the acetates provided separation of all four. Thin-layer chromatography on Silica Gel G separated the cis from the trans estriols. The trans epimers separated only on silica gel modified with ammonium bisulfate.
J C, Touchstone +2 more
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Sterol Metabolism X: Epimeric 23-Hydroxycholesterols
Journal of Pharmaceutical Sciences, 1970Abstract Synthesis of the epimeric 23-hydroxycholesterols has been achieved by sodium borohydride reduction of 3β-hydroxy-cholest-5-en-23-one.Tentative configurational assignments were made based on specific rotation data. The configurations of the epimeric 24-hydroxycholesterols are discussed, and a reconsideration of their configurational ...
J E, Van Lier, L L, Smith
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Kinetics of the epimeric glucocorticoid budesonide
Clinical Pharmacology and Therapeutics, 1984Budesonide is a potent nonhalogenated glucocorticoid consisting of a 1/1 mixture of the two epimers 22R and 22S. The kinetics of these epimers were studied in six healthy male subjects after intravenous administration of 500 micrograms 3H-budesonide. Estimation of the epimer concentrations in plasma was made possible by development of an HPLC method ...
A, Ryrfeldt, S, Edsbäcker, R, Pauwels
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