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101.
Summary Polarimetric and/or circular dichroic detection of enantiomers after liquid chromatography on optically active sorberts has
been used for the following purposes: determination of enantiomeric purity in spite of peak overlap, investigation of enantiomerization
during chromatography, monitoring of racemizations and recording of circular dichrograms without preparative enrichment of
enantiomers. Novel examples for all applications are give. The general prospects for chiroptical detection are discussed. 相似文献
102.
Pampel A Zick K Glauner H Engelke F 《Journal of the American Chemical Society》2004,126(31):9534-9535
An alternative technique for studying the lateral diffusion in lipid membranes using pulsed field gradients in combination with magic angle spinning is presented. It is shown that MAS probes inserted in a microimaging device that produce high field gradients can be used to monitor also slow diffusion processes. As an example, measurements of the lateral diffusion of lipids embedded in the bilayer of a cubic phase are presented. 相似文献
103.
Four new stationary phases for HPLC were prepared by modifying silica gel with a trifrnctional aminoalkyl silane. A conjugated π-electron system was linked to the amino group either directly or with a carboxylic anhydride as a spacer in between. Characterization and dynamic measurements of the new stationary phases were performed by solid state NMR spectroscopy. The results of the 29si and 13C CP/MAS techniques were compared with the recently developed 1H MAS-only technique. Despite strong homonuclear dipole-dipole interactions it was possible to obtain well resolved 1H MAS spectra of those stationaru phases with a high degree of crosslinking. Limited mobility of the aromatic ligand fragments is common for all examined stationaryu phases. The chromatographic properties of the new phases were tested by their ability tio sepatate a mixture of eight PAHS. It could be shown that the π-π interaction mechanism is responsible for the separation of the eight PAHs, because the elution order of the PAHs did not changem despite the use of both a nonpolar mobile phase (n-heptane) and a polar mobile phase (methanol/ water mixture). 相似文献
104.
The reaction of peri-substituted anthracenediones with sodium dithionite in dimethylformamide and water has been investigated. The system selectively reduces the carbonyl group flanked by the peri substituents of the anthracenediones to give the corresponding 4,5-disubstituted 9(10H)-anthracenones and thus provides a route to anthracenones which are otherwise difficult to obtain. Many functional groups can be tolerated, the reaction is compatible with the presence of peri alkoxy groups and unsaturated side chains of the starting anthracenediones, and the reduction does not go beyond the anthracenone stage. However, the formation of anthracenones depends on the nature of the peri substituents. No products were obtained from the 1,8-dimethyl-substituted anthracenedione and the parent compound with no substituents. 相似文献
105.
106.
Esahak Ali Ajit K. Chakravarty Satyesh C. Pakrashi Klaus Biemann Charles E. Hignite 《Tetrahedron》1977,33(11):1371-1377
The structure of solanoforthine, m.p. 208–10°, [α]D- 26.6°, a new steroidal alkaloid isolated from Solanum seaforthianum Andr., has been established as 3β-amino-22,26-epimino-16α,23-epoxy-22αH,25βH-cholest- 5- en -23β - ol 3, based on chemical and spectroscopic evidence and by its reduction to solanocapsine 2, another steroidal alkaloid encountered in the same species. The mass spectra of2 and 3 are discussed. 相似文献
107.
For the determination of flouride, chloride and bromide, a suitable metal ion is added in a modified graphite tube atomizer. After drying and ashing, the substances are vaporized and diatomic molecules between the metal and nonmetal are formed. These molecules are excited by a pulsed dye laser and the resulting fluorescence is measured. At constant metal concentration, the fluorescence is proportional to the halide concentration. The diatomic molecules used are MgF, InCl and AlBr. The detection limits are 11 pg of fluoride, 15 pg of chloride and 70 pg of bromide in the 10-μl injections, corresponding to 6 x 10?8 mol l?1 fluoride, 4 x 10?8 mol l?1 chloride and 9 x 10?8 mol l?1 bromides. 相似文献
108.
109.
A synthesis of all possible N-alkylated 2-n-butyl-imidazo[4,5]pyridine isomers is described as well as their structural assignment by 1H NMR spectroscopy. One of these derivatives, 2,-n-butyl-3-[2′- (1H-tetrazol-5-yl)-4-biphenylylmethyl]-3H-imidazo[4,5-b]pyridine 9 is a potent angiotensin II receptor antagonist. 相似文献
110.
Analytical and Bioanalytical Chemistry - 相似文献