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61.
Michał Rachwalski Szymon Jarzyński Marcin Jasiński Stanisław Leśniak 《Tetrahedron: Asymmetry》2013,24(11):689-693
A straightforward synthesis of a series of new catalysts containing secondary hydroxyl and aziridine moieties as nucleophilic centers built on the chiral scaffold of (S)-(+)-mandelic acid is described. The new compounds have been tested for the enantioselective addition of diethylzinc and phenylethynylzinc to aryl and alkyl aldehydes, which yielded the corresponding chiral alcohols in high chemical yields (up to 95%) and with excellent ee’s of ca. 90%. The strong influence of the stereogenic center located at the aziridine subunit on the stereochemical outcome is also reported on. 相似文献
62.
Mariusz J. Bosiak Judyta A. JakubowskaKrzysztof B. Aleksandrzak Szymon KamińskiAnna Kaczmarek-K?dziera Marta Ziegler-BorowskaDariusz K?dziera Jörg Adams 《Tetrahedron letters》2012,53(30):3923-3926
The synthesis of 2-(2-arylvinyl)- and 2,6-di(2-arylvinyl)dibenzo[1,2-b:4,5-b′]furan derivatives for application in optoelectronics is described. Wittig reaction of the triphenylphosphonium bromides derived from diethyl 2,6-dimethylbenzofuro[5,6-b]furan-3,7-dicarboxylate with aryl aldehydes gave the products in 70-99% yield. The corresponding products derived from furfural and cinnamic aldehyde were also obtained. The prepared products reveal UV-Vis fluorescence with quantum yields, varying from 1% to 100%, and may be used as organic small molecule materials for organic light-emitting devices (OLED). 相似文献
63.
The contour of a family of filters along a filter is a set-theoretic lower limit. Topologicity and regularity of convergences can be characterized with the aid of the contour operation. Contour inversion is studied, in particular, for iterated contours of sequential cascades. A related problem of continuous extension of maps between maximal elements of sequential cascades to full subcascades is solved in full generality. 相似文献
64.
A field-amplified sample injection (FASI) technique was elaborated for fast and sensitive determination of selected central nervous system drugs in human urine samples. Factors affecting the sensitivity enhancement, such as background electrolyte (BGE) and the analytical matrix composition were optimized and discussed. Pseudo-isotachophoresis (p-ITP) mechanism contribution in preconcentration mechanism was discussed. All separations were performed in uncoated fused silica capillaries 50 μm × 57 cm at 22 kV. The optimized analytical matrix was composed of 0.25 mM HCOOH in 90% (v/v) methanol, while BGE contained 45 mM TRIS/HCl (pH 2.20). The head-column injection was performed in 0.25 mM HCOOH water solution (3 s, 3.45 kPa). Sample was introduced into the capillary by electrokinetic injection (70 s, 5 kV) followed by short BGE plug (3 s, 3.45 kPa). Seven psychiatric drugs (olanzapine, prochlorperazine dimaleate, trifluoperazine dihydrochloride, perphenazine, promazine hydrochloride, clomipramine hydrochloride, and chlorprothixene hydrochloride) were separated in about 6 min. The elaborated method was additionally supported with dispersive liquid–liquid microextraction (DLLME) technique which in summary with FASI provided about 8000–13,000-fold sensitivity enhancement in comparison to the capillary zone electrophoresis (CZE) method with standard hydrodynamic injection (5 s, 3.45 kPa). 相似文献
65.
Szymon ?eberski 《Archive for Mathematical Logic》2011,50(3-4):423-430
Our main inspiration is the work in paper (Gitik and Shelah in Isr J Math 124(1):221?C242, 2001). We will prove that for a partition ${\mathcal{A}}$ of the real line into meager sets and for any sequence ${\mathcal{A}_n}$ of subsets of ${\mathcal{A}}$ one can find a sequence ${\mathcal{B}_n}$ such that ${\mathcal{B}_{n}}$ ??s are pairwise disjoint and have the same ??outer measure with respect to the ideal of meager sets??. We get?also generalization of this result to a class of ??-ideals posessing Suslin property. However, in that case we use additional set-theoretical assumption about non-existing of quasi-measurable cardinal below continuum. 相似文献
66.
Comparison of four cholesterol‐based stationary phases for the separation of steroid hormones
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Jan Soukup Szymon Bocian Pavel Jandera Bogusław Buszewski 《Journal of separation science》2014,37(4):345-351
The chromatographic behavior of steroid hormones on four cholesterol‐bonded stationary phases with different structures in binary methanol/water mobile phases was studied. Of the stationary phases tested, the commercially available stationary phases Cogent UDC cholesterol? and COSMOSIL cholester? provided better separations of steroid hormones in comparison to homemade aminocholesterol and diaminocholesterol stationary phases. The results show that the temperature has a significant influence on the retention and selectivity for steroid hormones separation. The temperature increase may cause changes in the elution order. From the dependences of the retention (ln k) on temperature (1/T), the standard partial molar enthalpy and standard partial molar entropy were calculated and their enthalpic and entropic contributions to the retention were compared. The enthalpic effects principally control the retention mechanism. 相似文献
67.
Synthesis of Spirocyclic Enones by Rhodium‐Catalyzed Dearomatizing Oxidative Annulation of 2‐Alkenylphenols with Alkynes and Enynes
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Szymon Kujawa Dr. Daniel Best Dr. David J. Burns Prof. Hon Wai Lam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8599-8602
The dearomatizing oxidative annulation of 2‐alkenylphenols with alkynes and enynes proceeds with high yields and regioselectivities under RhIII catalysis. These reactions are successful using Cu(OAc)2 or air as the stoichiometric oxidant, and provide spirocyclic enones, the basic ring system of which appears in several natural products. Application of this process to the preparation of a highly functionalized tetracycle is also demonstrated. 相似文献
68.
Szymon Dziomba Magdalena Wysocka Joanna Jońca Laura Sola Aleksandra Steć Krzysztof Waleron Bartosz Wielgomas 《Electrophoresis》2021,42(20):2010-2017
The capillary zone electrophoresis (CZE) has recently been proposed by our group as a novel technique for outer membrane vesicles (OMVs) characterization (J. Chromatography 1621 (2020) 461047). In present work the impact of selected parameters of CZE method on OMVs isolates analysis was assessed. It was shown that the extension of sample injection plug length significantly improves the detectability of macromolecular aggregates in CZE. Moreover, a negligible adsorption of OMVs to both uncoated and polymer-modified (poly(DMA-GMA-MAPS)) capillary walls was proven. Finally, the relaxation effect as well as deformation/polarization of vesicles were demonstrated to affect OMVs electrophoretic mobility. The significance of these findings was discussed. 相似文献
69.
Aneta M. Tomkiel Dorota Czajkowska-Szczykowska Ewa Olchowik-Grabarek Lucie Rrov Szymon Skowski Jacek W. Morzycki 《Molecules (Basel, Switzerland)》2023,28(1)
A chemoselective procedure for MCPBA oxidation of 26-thiodiosgenin to corresponding sulfoxides and sulfone was elaborated. An unusual equilibration of sulfoxides in solution was observed. Moreover, α-alkylation of sulfoxide and sulfone was investigated. Finally, the biological activity of obtained compounds was examined. 相似文献
70.
Szymon Poliski Patrycja Topka Magorzata Taska Sylwia Kowalska Sylwester Czaplicki Aleksandra Szydowska-Czerniak 《Molecules (Basel, Switzerland)》2022,27(21)
The aim of this study was to optimize the grinding process parameters (mesh size of grinder sieve (X1), the peripheral velocity of the grinding wheels (X2)), and the storage time (X3) of ground ginger rhizome and nutmeg to obtain ethanol and ethanol-water extracts with improved antioxidant properties. The optimal conditions were estimated using response surface methodology (RSM) based on a three-variable Box–Behnken design (BBD) in order to maximize the antioxidant capacity (AC) determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods, and the total phenolic content (TPC) was determined by the Folin–Ciocalteu (F–C) method in spice extracts. Additionally, the phenolic acid profiles in extracts from optimized conditions were analyzed using ultra-performance liquid chromatography (UPLC). It was found that the optimal preparation conditions for antioxidant extraction were dependent on the spice source and solvent type. The best antioxidant properties in nutmeg extracts were achieved for X1 = 1.0 mm, X2 = 40–41 Hz and X3 = 7 days, whereas the optimized parameters for ginger extracts were more varied (1.0–2.0 mm, 43–50 Hz and 1–9 days, respectively). The ginger extracts contained 1.5–1.8 times more phenolic acids, and vanillic, ferulic, gallic, and p-OH-benzoic acids were dominant. In contrast, the nutmeg extracts were rich in protocatechuic, vanillic, and ferulic acids. 相似文献