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1.
Herein, we report an addition to the toolbox for the monitoring and quantification of the hydrolytic decay of pentose-1-phosphates, which are known to be elusive and difficult to quantify. This communication describes how apparent equilibrium shifts of a nucleoside phosphorolysis reaction can be employed to calculate hydrolytic loss of pentose-1-phosphates based on the measurement of post-hydrolysis equilibrium concentrations of a nucleoside and a nucleobase. To demonstrate this approach, we assessed the stability of the relatively stable ribose-1-phosphate at 98 °C and found half-lives of 1.8–11.7 h depending on the medium pH. This approach can be extended to other sugar phosphates and related reaction systems to quantify the stability of UV-inactive and hard-to-detect reaction products and intermediates. 相似文献
2.
Helmut Schmidhammer Felizia Kaspar Arpad Marki Anna Borsodi 《Helvetica chimica acta》1994,77(4):999-1002
The mixed azines 4 and 5 were prepared by reaction of naloxazone ( 2 ) with either oxymorphone ( 6 ) or 14-O-methyloxymorphone ( 7 ) and tested in vitro using opioid receptor binding assays and in vivo using the AcOH-writhing test in mice. Compound 4 was found to be a partial agonist, while compound 5 was a potent opioid agonist with higher potency than morphine. 相似文献
3.
Kaspar Hegetschweiler Isidor Erni Walter Schneider Helmut Schmalle 《Helvetica chimica acta》1990,73(1):97-105
1,3,5-Trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (TDCI) and 1,3,5-trideoxy-1,3,5-tris(trimethylammonio)-cis-inositol (TTCI) were prepared by methylation of 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (TACI). The ability of TDCI to form both intermolecular and intramolecular H-bonds, as demonstrated by X-ray diffraction, is probably responsible for the good solubility of TDCI in almost every common solvent. TTCI was found to be a polyol of unusual high acidity (pK1 = 8.14 ± 0.02, pK2 = 13.0 ± 0.2). This phenomenon could be explained by electrostatic interactions between the charged substituents of the cyclohexane residue. 相似文献
4.
5.
For the major, minor and trace element analysis of the inorganic compounds of a Ruhr-Saar coal different preparation techniques are investigated with X-ray fluorescence analysis, electron microprobe and classical wet chemical methods minimizing sample weight at standard preparation times and analytical accuracies. Considering accuracy as well as preparation efforts, determinations by electron microprobe on small sample amounts (<50 mg) proved to be superior to the other methods.Abbreviations AAS
atomic absorbtion spectrometry
- EMA
electron microprobe analysis
- IC
ion chromatography
- ISE
ion sensitive electrode
- PHOT
photometry
- WCA
wet chemical analysis
- XRF
X-ray fluorescence analysis
- LTA
low temperature plasma ashing
- HTA
high temperature ashing
- l.o.i.
loss on ignition 相似文献
6.
7.
Kaspar Bott 《Angewandte Chemie (International ed. in English)》1980,19(3):171-178
Numerous additions of carbocations to chloroolefins or acetylenes can be coupled with a solvolysis step when performed in a suitable acid; the products are variously substituted carboxylic acids, aldehydes, and ketones. Factors determining the success of these syntheses are the stability of the intermediate carbocations and suppression of the competing addition of protons to the unsaturated reaction component. Under the conditions of the Tscherniac-Einhorn reaction, amidomethylation of chloroolefins and acetylenes, i.e. the introduction of acylaminomethyl groups, is shown not to involve a trigonal α-chloro carbocation or a linear vinyl cation, but instead to proceed via a cyclic oxazinium ion intermediate. 相似文献
8.
The complexes [Fe(tdci)2]Cl3 and [Al(tdci)2]Cl3 (tdci = 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol) were prepared and characterized by mass spectrometry, NMR spectroscopy, and magnetic-susceptibility measurements. The formation constants were determined in aqueous solution (25°, 0.1M KCl) by potentiometric titration. pK values of H3(tdci)3+: 5.89, 7.62, 9.68; FeIII complexes: log βML = 18.8, log β = 32.6; AlIII complexes: log βML = 14.3, logβ = 26.4. The protonated complex [FeH(tdci)2]4+ has also been identified. In contrast to the high stability of the FeIII and AlIII complexes, only weak interactions of tdci with CuII have been observed in aqueous solution (25°, 0.1M KNO3). 相似文献
9.
By irradiation, the tetrahydropyranylarylketoacetal compounds led to isomers of spiro compounds. A competition between Norrish II and Paterno-Buchi reations was observed with unsaturated heterocyclic products. In the osidic series, the reaction was not stereoselective, but the photocyclisation works with rentention of configuration at low temperature. The acidic epimerisation of spiro C-1 sugars mainly yields the trans (α or β) isomers. 相似文献
10.