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71.
A simple reaction scheme and kinetic data are presented for the oxidation of 2,6-xylenol by Co(III) chelates in toluene.
2,6- Co(III) .相似文献
72.
73.
Ohne Zusammenfassung 相似文献
74.
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76.
Majer J. 《Colloid and polymer science》1962,184(1):90
Ohne Zusammenfassung 相似文献
77.
Schmid DG Majer F Kupke T Jung G 《Rapid communications in mass spectrometry : RCM》2002,16(18):1779-1784
The microbial flavoenzyme EpiD catalyzes the oxidative decarboxylation of peptidyl-cysteines to peptidyl-aminoenethiols. These unusual C-terminally modified peptides are intermediates in the biosynthesis of the tetracyclic peptide antibiotic epidermin, which belongs to the lantibiotics family. The peptide SFNSYCC represents the C-terminal partial sequence of the natural precursor peptide EpiA. EpiA is posttranslationally modified to form finally the lantibiotic epidermin. The substrate specificity of EpiD was investigated using high-resolution mass spectrometry and the heptapeptide library SFNSXCC. The enzymatic conversion of particular peptides can be observed by a mass loss of m/z 46. In contrast to the previously used triple quadrupole instrument, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was able to resolve and detect all precursor and converted peptides with identical nominal masses in a single measurement, avoiding the necessity to investigate single peptides. Furthermore, a new substrate SFNSCCC of the enzyme EpiD was detected within the reaction mixture. 相似文献
78.
John J. Morelli Somayajula K. Viswanadham Andrew. G. Sharkey JR. David M. Hercules 《International journal of environmental analytical chemistry》2013,93(2-4):295-323
Abstract Laser mass spectra obtained for 20 organophosphorus (OP) compounds were systematically evaluated for groups containing analogous structural features. Variations in fragmentation can be understood based on simple organic reactions. While detailed mechanistic interpretations of the laser mass spectra (LMS) were not possible, the qualitative features in the LMS obtained from five compounds, not in the original set, could be predicted based on the characteristics of the other OP compounds studied. The success of the prediction lends credence to the qualitative models developed for rationalizing the LMS. A specific feature in the LMS of aromatic thionophosphates is a thiono-thiolo rearrangement. Detailed investigation into the phenomena involved comparison of LMS obtained from aromatic thionophosphates with spectra from electron impact, chemical ionization, field desorption, and secondary ion mass spectrometry. These results led to the conclusion that the rearrangement in laser mass spectrometry must occur during volatilization while the molecule/ion is in the “cloud” present immediately above the laser impact area. 相似文献
79.
We demonstrate a new approach for the asymmetric synthesis of bissetone. The key reaction is the highly enantioselective hetero-Diels–Alder cycloaddition of triene 3 with ethyl glyoxylate catalyzed by readily available BINOL–Ti complexes. The HDA cycloadduct 4 was then transformed in five steps into O-protected bissetone (8) and its C5-epimer in good yield. 相似文献
80.
Several low molecular weight alkanes have been polymerized (polycondensed) over HSO3 F-SbF5 to yield a highly branched oily oligomer with a molecular weight range from the molecular weight of the monomer to around 700. The order of reactivity for butane and lower molecular alkanes is isobutane > n-butane > propane > ethane > methane. The reactivity is explained by the ease of attack of an acid proton derived from the acid on the alkane sigma bonds as well as the relative stability of the resulting cation formed. A cationic mechanism for this reaction is proposed. 相似文献