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981.
New derivatives of 5-aryl-2-[2-(2-furyl)ethenyl]-1,3,4-oxadiazoles and 5-aryl-2-[2-(2-thienyl)ethenyl]-1,3,4-oxadiazoles are synthesized in a stepwise procedure through intermediate acyclic N′-arylcarbonyl-N-[2-(2-heteroaryl)acryloyl]hydrazines, starting from 3-(2-heteroaryl)acrylic acid hydrazides and acid chlorides. A facile one-pot methodology leading to the final 1,3,4-oxadiazoles is also described. 相似文献
982.
This Letter describes an attractive and efficient method for Mg(OR)2-mediated lactide alcoholysis. The catalysts were generated in situ from di-n-butylmagnesium and ROH to prevent aggregation of Mg(OR)2. The reaction of ROH [R = Me, Et, RCO2(Me)CH] with lactide initially yielded the ring-opened product HO[CH(CH3)CO]nOR (n = 2 or 3). The complete consumption of lactide caused the reaction to proceed further, giving environmentally friendly lactic acid esters in excellent yields under ambient conditions. 相似文献
983.
Andrzej Bobrowski Mariola Maczuga Agnieszka Królicka Evangelia Konstanteli Chrysavgi Sakellaropoulou Anastasios Economou 《Analytical letters》2017,50(18):2920-2936
The voltammetric performance of an in situ plated antimony film screen-printed carbon electrode in hydrochloric acid, acetate buffer, and tartrate buffer was evaluated for the detection of copper(II) with differential pulse anodic stripping voltammetry. The tartrate buffer was superior, providing high sensitivity and good separation of copper and antimony stripping peaks. The analytical conditions for the determination of copper(II) were optimized. The detection limit was estimated to be 0.14?µg?L?1 copper(II) and the relative standard deviation for 2.5?µg?L?1 copper(II) was 3%. The applicability of the method was illustrated by the analysis of soil conditioner samples. 相似文献
984.
985.
Krzysztof Durka Agnieszka Górska Piotr Jankowski Tomasz Kliś Marcin Kublicki Janusz Serwatowski Mateusz Urban Grzegorz Wesela-Bauman Krzysztof Woźniak 《Tetrahedron letters》2017,58(12):1185-1189
A one-pot protocol was developed for the synthesis of a series of luminescent heteroleptic diaryldiborinic complexes containing the central aryl ring bonded to two boron atoms substituted with pyrazole and complexed with 8-hydroxyquinoline. The luminescent properties of these compounds were measured. In dilute solutions they exhibited an emission at ca. 513 nm with quantum yields of 22–27% which are typical for borinic 8-hydroxyquinoline complexes. The only exception was the complex containing the bithiophene scaffold, for which no fluorescence was observed. The obtained pyrazole-based complexes show improved solubility and thermal stability with respect to their phenyl analogues. The experimental UV–vis absorption and emission data are supported by theoretical calculations of the frontier molecular orbitals, revealing the aromatic linker to quinolinato ligand excitation mechanism. 相似文献
986.
Elżbieta Studzińska-Sroka Elżbieta Hołderna-Kędzia Agnieszka Galanty Wiesława Bylka Karol Kacprzak Karolina Ćwiklińska 《Natural product research》2015,29(24):2302-2307
Heptane (Hep), diethyl ether (Et2O), acetone (Me2CO) and methanolic (MeOH) extracts, as well as ( ? )-usnic acid and squamatic acid, were obtained from thallus of Cladonia uncialis (Cladoniaceae). The antimicrobial activities of these extracts, ( ? )-usnic acid and squamatic acid, were tested against reference strains: Staphylococcus aureus, Escherichia coli and Candida albicans. In addition, Me2CO extract was analysed against 10 strains of Methicillin-resistant S. aureus (MRSA) isolated from patients. All extracts exerted antibacterial activity against the reference strain S. aureus, comparably to chloramphenicol [minimum inhibitory concentration (MIC) = 5.0 μg/mL]. The Me2CO extract exhibited the strongest activity against S. aureus (MIC = 0.5 μg/mL), higher than ( ? )-usnic acid, whereas squamatic acid proved inactive. The Me2CO extract showed potent antimicrobial activity against MRSA (MIC 2.5–7.5 μg/mL). Also no activity of C. uncialis extracts against E. coli and C. albicans was observed. 相似文献
987.
Poornima Vijayan P Debora Puglia Agnieszka Dąbrowska Pournami Vijayan P Andrzej Huczko Jose M. Kenny Sabu Thomas 《先进技术聚合物》2015,26(2):142-146
The silicon carbide (SiC) nanofibers (0.1, 0.25, and 0.5 phr), produced by self‐propagating high‐temperature synthesis (SHS), are used to reinforce the epoxy matrix cured with an anhydride hardener. Morphological studies reveal a better dispersion of SiC nanofibers and a good level of adhesion between nanofiber and the matrix in composites with lower (0.1 and 0.25 phr) nanofiber loading. The flexural studies show that a maximum increase in flexural properties is obtained for composites with 0.25 phr SiC nanofiber. The fracture toughness of epoxy is found to increase with the incorporation of SiC nanofibers, and 0.25 phr SiC nanofiber loading shows maximum fracture toughness value. The possible fracture mechanisms that exist in epoxy/SiC nanofiber composites have been investigated in detail. Thermogravimetric analysis reveals that SiC nanofibers are effective fillers to improve the thermal stability of epoxy matrix. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
988.
Dr. Simon J. White Dr. Steven D. Johnson Mark A. Sellick Dr. Agnieszka Bronowska Prof. Peter G. Stockley Prof. Christoph Wälti 《Angewandte Chemie (International ed. in English)》2015,54(3):974-978
Molecular crowding plays a significant role in regulating molecular conformation in cellular environments. It is also likely to be important wherever high molecular densities are required, for example in surface‐phase studies, in which molecular densities generally far exceed those observed in solution. Using on‐surface circular dichroism (CD) spectroscopy, we have investigated the structure of a synthetic peptide assembled into a highly packed monolayer. The immobilized peptide undergoes a structural transition between α‐helical and random coil conformation upon changes in pH and ionic concentration, but critically the threshold for conformational change is altered dramatically by molecular crowding within the peptide monolayer. This study highlights the often overlooked role molecular crowding plays in regulating molecular structure and function in surface‐phase studies of biological molecules. 相似文献
989.
990.