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排序方式: 共有387条查询结果,搜索用时 15 毫秒
51.
The copper(II) complex of a modified cyclodextrin, namely 6-mono-deoxy-6-[4-(2-aminoethyl)imidazolyl]-β-CD (CDmh), previously synthesized and characterized in our laboratory and already used as chiral selector for ligand exchange capillary electrophoresis (LECE) with optical detection, is investigated here in LECE using electrospray-mass spectrometry (ESI-MS) as the detection device. The potential of this hyphenated method is compared with the results previously obtained with optical detection by studying the chiral resolution of tryptophan racemate. Chiral separation conditions compatible with LECE-ESI-MS could be achieved based on the figures of merit obtained by LECE-UV. Interestingly, the values of LOD obtained by LECE-ESI-MS were significantly better than those obtained by LECE-UV and thus, ESI-MS detection seems to open new perspectives in chiral separations by LECE. 相似文献
52.
Pizzetti M Russo A Petricci E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4523-4528
The microwave-assisted aminocarbonylation of ynamides at low pressures of CO is reported. A new class of (E)-acrylamides that are potentially suitable for several applications has been regioselectively synthesized after microwave irradiation for only 20 min by using eco-friendly [Fe(3)(CO)(12)] as the catalyst precursor and triethylamine as the ligand. This transformation is atom economic as all reactants are used in stoichiometric quantities. Furthermore, the transformation is efficiently applied to the alkoxycarbonylation of alkynes as well. Moreover, running these reactions under microwave irradiation allows the simplification of the reaction conditions with remarkable reductions in time, temperature and gas pressure. 相似文献
53.
Carbone M Li Y Irace C Mollo E Castelluccio F Di Pascale A Cimino G Santamaria R Guo YW Gavagnin M 《Organic letters》2011,13(10):2516-2519
Two indole alkaloids, phidianidines A (1) and B (2), exhibiting an uncommon 1,2,4-oxadiazole ring linked to the indole system, have been isolated from the marine opisthobranch mollusk Phidiana militaris. The structures of the two metabolites have been elucidated by spectroscopic techniques. Phidianidines exhibit high cytotoxicity against tumor and nontumor mammalian cell lines in in vitro assays. 相似文献
54.
Imre Miklós Szilágyi Eero Santala Mikko Heikkilä Marianna Kemell Timur Nikitin Leonid Khriachtchev Markku Räsänen Mikko Ritala Markku Leskelä 《Journal of Thermal Analysis and Calorimetry》2011,105(1):73-81
This article demonstrates how important it is to find the optimal heating conditions when electrospun organic/inorganic composite
fibers are annealed to get ceramic nanofibers in appropriate quality (crystal structure, composition, and morphology) and
to avoid their disintegration. Polyvinylpyrrolidone [PVP, (C6H9NO)
n
] and ammonium metatungstate [AMT, (NH4)6[H2W12O40]·nH2O] nanofibers were prepared by electrospinning aqueous solutions of PVP and AMT. The as-spun fibers and their annealing were
characterized by TG/DTA-MS, XRD, SEM, Raman, and FTIR measurements. The 400–600 nm thick and tens of micrometer long PVP/AMT
fibers decomposed thermally in air in four steps, and pure monoclinic WO3 nanofibers formed between 500 and 600 °C. When a too high heating rate and heating temperature (10 °C min−1, 600 °C) were used, the WO3 nanofibers completely disintegrated. At lower heating rate but too high temperature (1 °C min−1, 600 °C), the fibers broke into rods. If the heating rate was adequate, but the annealing temperature was too low (1 °C min−1, 500 °C), the nanofiber morphology was excellent, but the sample was less crystalline. When the optimal heating rate and
temperature (1 °C min−1, 550 °C) were applied, WO3 nanofibers with excellent morphology (250 nm thick and tens of micrometer long nanofibers, which consisted of 20–80 nm particles)
and crystallinity (monoclinic WO3) were obtained. The FTIR and Raman measurements confirmed that with these heating parameters the organic matter was effectively
removed from the nanofibers and monoclinic WO3 was present in a highly crystalline and ordered form. 相似文献
55.
Lúcio AS Almeida JR Barbosa-Filho JM Pita JC Branco MV Diniz Mde F Agra Mde F da-Cunha EV da Silva MS Tavares JF 《Molecules (Basel, Switzerland)》2011,16(8):7125-7131
Phytochemical investigation of Anaxagorea dolichocarpa Sprague & Sandwith led to isolation of three azaphenanthrene alkaloids: eupolauramine, sampangine and imbiline 1. Their chemical structures were established on the basis of spectroscopic data from IR, HR-ESI-MS, NMR (including 2D experiments) and comparison with the literature. Sampangine and imbiline 1 are being described in the Anaxagorea genus for the first time. Eupolauramine and sampangine show concentration-dependent antitumoral activity in leukemic cells K562 with IC(50) of 18.97 and 10.95 μg/mL, respectively. 相似文献
56.
Two unprecedented degraded sterols, aplykurodinone-1 (1) and -2 (2), have been isolated from the skin of the marine anaspidean Syphonota geographica, collected along the coasts of Greece. The structures and the relative stereochemistry were established by spectroscopic analysis and confirmed by chemical correlation with related known compounds. 相似文献
57.
ágnes Horváth István Hermecz Marianna Pongor-Csákvári Zoltán Mészáros József Kökösi Gábor Tóth áron Szöllósy 《Journal of heterocyclic chemistry》1984,21(1):219-224
The structures of the title compounds bearing a five-, six- or seven-membered A ring have been investigated by uv and 1H and 13C nmr spectroscopy. The imine-enol-enamine (I-II-III) tautomerism of these compounds depends greatly on the ring size. A significant solvent-dependence is observed only for the five-membered-ring compounds 1 and 2 , which in ethanolic solution exist predominantly in the imine form I, and in chloroform solution in the enol form II. The compounds with a six-membered A ring, 3 and 4 , are mainly in the enamine form III. On protonation, 3 and 4 change into the E and Z isomeric mixture of the enol tautomer II. The seven-membered-ring compound 5 is a mixture of the imine I and the enamine III tautomers. 相似文献
58.
Marianna Csörnyei Paul D. Humke 《Journal of Mathematical Analysis and Applications》2005,305(2):546-559
Properties of first-return integrals of real functions defined on the unit interval are explored. In particular, first-return integrals are shown to be continuous but not absolutely continuous. 相似文献
59.
60.
Veronica Zaconte Marco Casolino Luca Di Fino Chiara La Tessa Marianna Larosa Livio Narici Piergiorgio Picozza 《Radiation measurements》2010,45(2):168-172
The ALTEA (Anomalous Long Term Effects on Astronauts) detector was used to characterize the radiation environment inside the USLab of the International Space Station (ISS), where it measured the abundances of ions from Be to Fe. We compare the ALTEA results with Alteino results obtained in the PIRS module of the Russian segment of the ISS, and normalize to the high energy Si abundances given by Simpson. These are the first particle spectral measurements, which include ions up to Fe, performed in the USLab. The small differences observed between those made inside the USLab and the Simpson abundances can be attributed to the transport through the spacecraft hull. However, the low abundance of Fe cannot be attributed to only this process. 相似文献