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Inna P. Tsypysheva Alexander N. Lobov Alena V. Kovalskaya Valentina I. Vinogradova Kyrill Yu. Suponitsky Sergey L. Khursan Marat S. Yunusov 《Tetrahedron: Asymmetry》2013,24(20):1318-1323
The Diels–Alder adducts of the quinolizidine alkaloids N-methylcytisine, (?)-leontidine, and (?)-thermopsine with N-phenylmaleimide have been synthesized. The structures and absolute configurations of the new asymmetric centers of the products were determined by NMR spectroscopy experiments, QC-calculations, and X-ray data. 相似文献
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Dr. Rebecca L. Greenaway Dr. Valentina Santolini Dr. Filip T. Szczypiński Dr. Michael J. Bennison Dr. Marc A. Little Andrew Marsh Dr. Kim E. Jelfs Prof. Andrew I. Cooper 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3718-3722
Molecular dumbbells with organic cage capping units were synthesised via a multi-component imine condensation between a tri-topic amine and di- and tetra-topic aldehydes. This is an example of self-sorting, which can be rationalised by computational modelling. 相似文献
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The Ramanujan Journal - Let $$D_h$$ , $$E_k$$ and $$F_{\alpha }$$ be sets of size $$h,k,\alpha $$ respectively, with $$k \le h$$ . We define a strongly widened derangement to be a permutation of... 相似文献
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Rosário Monteiro Gil Faria Manuela Meireles Luísa Correia‐Sá Diana Teixeira Ana Faria Conceição Calhau Valentina F. Domingues Cristina Delerue‐Matos 《Biomedical chromatography : BMC》2012,26(12):1494-1501
Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C18‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP18 SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C18‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Mikhail I. Smushkin Valentina G. Kharchenko Boris I. Drevko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):621-624
It is shown using 1H NMR spectroscopy that 2,4,6-triphenyl-4H-seleno(thio)pyrans can be isomerized into 2H-isomers by the action of lithium perchlorate or lithium chloride in DMF or only by DMF. The reaction time is found to depend on the Lewis acidity of used salt. It is supposed that isomerization in presence of Lewis acids proceeds as endocyclic 1,3-proton transfer or as a series of two 1,2-hydride shifts. 相似文献
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