Search results for "nuclear magnetic resonance"
showing 10 items of 1743 documents
Predominance of resonance over polar effects on1H,13C and15N NMR substituent chemical shifts inN-arylglycines
1998
13C nuclear magnetic resonance spectra of several podocarpane and cassane diterpenoids
1990
The 13C NMR spectra of several diterpenic derivatives having the podocarpane and cassane skeleton were recorded and interpreted. The most significant effects due to substituent orientation, B/C ring junction stereochemistry and conformational changes are briefly discussed.
Antidiabetische wirkstoffe. V Lang- und verzweigtkettig substituierte chlor-dihexylamino-1,3,5-triazine
1985
Die nucleophile Substitution eines Chloratoms in 2,4-Dichlor-6-dihexylamino-1,3,5-triazin (1) durch Amine (2a-c) fuhrt zu den Alkylamino-chlor-dihexylamino-1,3,5-triazinen 3a-c. Fur Strukturtyp 3 typische Signale in den 1H-NMR-Spektren sind das Triplett bei 0,9 ppm fur die endstandigen Methylgruppen und das Multiplett bei 3,3-3,65 ppm fur die den Stickstoffatomen benachbarten Methylengruppen. In Verbindungsklasse 3 finden sich Vertreter mit antidiabetischer, trichomonazider, antiviraler und anthelminthischer Wirksamkeit. The nucleophilic substitution of one chlorine atom in 2,4-dichloro-6-dihexylamino-1,3,5-triazine (1) by amines 2a-c leads to the alkylamino-chlorodihexylamino-1,3,5-triazin…
New Sesquiterpene Lactones and Other Constituents fromCentaurea paui
1997
Aerial parts of Centaurea paui afforded, in addition to several known sesquiterpene lactones, the two new elemanolides 2–4, the new elemane derivative 5 as well as the five new heliangolides 14–18. Their structures were elucidated by spectroscopic methods, especially high-field NMR spectroscopy. The structure of the heliangolide 12 previously isolated from this plant, has been confirmed by X-ray diffraction.
Trichomonazide Wirkstoffe, 2. Mitt. Verzweigtkettig 4,6-disubstituierte 2-Cyanaminopyrimidine
1985
Aus der Umsetzung von Dicyandiamid (1) mit den β-Diketonen 2a–b gehen die 4,6-verzweigtkettig disubstituierten 2-Cyanaminopyrimidine 3a–b hervor. Fur Strukturtyp 3 last sich aus den spektroskopischen Daten, speziell aus den 1H- und 13C-NMR-Werten, das Vorliegen eines Gleichgewichts zwischen den tautomeren 2-Cyanamino- und 2-Cyaniminopyrimidinformen ableiten. 3 zeichnet sich durch trichomonazide, antivirale und antimykotische Wirkung aus. Trichomonacidal Agents, II: 4,6-Disubstituted 2-(Cyanoamino)pyrimidines Carrying Branched Substituents The reaction of dicyandiamide (1) with the β-diketones 2a–b yields the 4,6-branched disubstituted 2-(cyanoamino)pyrimidines 3a–b. From spectroscopic evide…
Synthesis of chemisorbed imidazolium and phosphonium cations by reaction of ionic liquid precursors with silica.
2010
The reaction of four different basic ionic liquid precursors with Aerosil®300 is presented. Chemisorbed imidazolium and phosphonium cations, with silanolate anions as part of the silicatic support, were obtained and investigated with various solid state NMR techniques.
Stereocontrolledα-Alkylation of Fully ProtectedL-Serine
2004
Diastereoselective alkylation of the (2S,4S) and (2R,4S) diastereomers of 3-tert-butyl 4-methyl 2-tert-butyl-1,3-oxazolidine-3,4-dicarboxylate (1a/b) is reported. Formation of both diastereomers of these oxazolidines was achieved by changing the order of protection steps, and their relative and absolute configurations were determined by NOESY spectroscopy. The use of the bulky ring substituent tBu together with Boc as the N-protecting group led to the exclusive formation of only one alkylated diastereomer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Benzodiselenagermoles and spirobisbenzodiselenagermoles
1993
Synthesis of benzodiselenagermoles and bisbenzodiselenagermoles was carried out by transmetallation group 4 group 14 between diselenophenylenezirconocenes and dialkyl-, diaryl- or alkylaryldichlorogermanes, aryltrichlorogermane or germanium tetrachloride. The new compounds were studied by 1H, 77Se NMR and mass spectrometry. In the case of compounds with substituted phenyl groups, double irradiation and 2D NMR experiments were performed to determine the chemical shifts of the two selenium atoms. The crystal structure of a spirobisbenzodiselenagermole has been established by X-ray diffraction analysis.
Multinuclear magnetic resonance study of 1,3,3-trimethylbicyclo [2.2.1]heptan-2-one (fenchone) oxime, its five monochloro derivatives and a dehydroch…
1991
Fenchone oxime, 5-exo-chlorofenchone oxime, 6-exo-chlorofenchone oxime, 7-anti-chlorofenchone oxime, 8-chlorofenchone oxime, 9-chlorofenchone oxime and a dehydrochlorination product of 10-chlorofenchone oxime were synthesized from fenchone and the corresponding chlorofenchones. The 1H, 13C and 17O NMR spectra of the oximes and the dehydrochlorination product were recorded. The NMR data were compared with the corresponding parameters obtained earlier for fenchone and monochlorofenchones in order to determine the differences between the carbonyl and oxime substituents from the NMR spectroscopic point of view, and to assign the stereochemistry of the oxime group. This stereochemistry could not…
NMR-Spektroskopie an Heterocyclen, 5. Mitt.13C-NMR- und massenspektrometrische Untersuchung N-substituierter Methoxy- und Hydroxy-äthylimidazole
1978
Es wird die 13C-NMR- und massenspektrometrische Untersuchung verschiedener N-substituierter Methoxy- und Hydroxy-athylimidazole beschrieben. Fur den Zerfall von 1,2-Diathyl-4-(2-hydroxyathyl)-imidazol wird ein ausfuhrliches Fragmentierungsschema angegeben. NMR-Spectroscopy of Heterocyclic Compounds, V: 13C-NMR and Mass Spectrometry of N-Substituted (2-Methoxyethyl)- and (2-Hydroxyethyl)-imidazoles The 13C-NMR and mass spectra of various N-substituted (2-methoxyethyl)- and (2-hydroxyethyl)imidazoles are described. A scheme for the fragmentation of 1,2-diethyl-4-(2-hydroxyethyl)imidazole is reported.