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71.
Inside Back Cover: Spectroscopic and Kinetic Evidence for the Crucial Role of Compound 0 in the P450cam‐Catalyzed Hydroxylation of Camphor by Hydrogen Peroxide (Chem. Eur. J. 43/2015) 下载免费PDF全文
Dr. Alicja Franke Prof. Dr. Rudi van Eldik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15447-15447
72.
Cover Picture: Drug Metabolism by Cytochrome P450 Enzymes: What Distinguishes the Pathways Leading to Substrate Hydroxylation Over Desaturation? (Chem. Eur. J. 25/2015) 下载免费PDF全文
73.
Enantiomeric Enrichments via the Self‐Disproportionation of Enantiomers (SDE) by Achiral,Gravity‐Driven Column Chromatography: a Case Study Using N‐(1‐Phenylethyl)acetamide for Optimizing the Enantiomerically Pure Yield and Magnitude of the SDE 下载免费PDF全文
Alicja Wzorek Azusa Sato Józef Drabowicz Vadim A. Soloshonok Karel D. Klika 《Helvetica chimica acta》2015,98(8):1147-1159
This work explores the self‐disproportionation of enantiomers (SDE) via achiral, gravity‐driven column chromatography as typically used in laboratory settings for the purpose of enantiomeric enrichment using N‐(1‐phenylethyl)acetamide (PEA) as a case study. The major finding of this work is the very large magnitude of the SDE for PEA across a variety of conditions and broad range of starting ee values, thereby facilitating a simple, reliable, and predictable means of obtaining enantiomerically pure samples. For example, starting with a sample of PEA of ee as low as 28%, a single column run yielded an enantiomerically pure sample (>99.9% ee) from the first fractions and a significantly enantiomerically depleted sample (<17% ee) from the final fractions. An assessment of SDE via achiral, gravity‐driven column chromatography was also rendered with regard to the differing objectives that workers might target – a large magnitude of the SDE, obtaining an optimum sample of desired ee, or preparative‐scale separation of the excess enantiomer. Overall, it can be considered that the SDE phenomenon via achiral, gravity‐driven column chromatography – readily applicable in the usual laboratory settings – is a simple and convenient method for enantiomeric enrichment with a high degree of proficiency. Advantages of SDE via achiral, gravity‐driven column chromatography over conventional fractional recrystallization for the enantiomeric enrichment of amides/amines, and applicable also to many other classes of compounds as well, are discussed. 相似文献
74.
The reaction of the water-soluble Fe(III)(TMPS) porphyrin with CN(-) in basic solution leads to the stepwise formation of Fe(III)(TMPS)(CN)(H(2)O) and Fe(III)(TMPS)(CN)(2). The kinetics of the reaction of CN(-) with Fe(III)(TMPS)(CN)(H(2)O) was studied as a function of temperature and pressure. The positive value of the activation volume for the formation of Fe(III)(TMPS)(CN)(2) is consistent with the operation of a dissociatively activated mechanism and confirms the six-coordinate nature of the monocyano complex. A good agreement between the rate constants at pH 8 and 9 for the formation of the dicyano complex implies the presence of water in the axial position trans to coordinated cyanide in the monocyano complex and eliminates the existence of Fe(III)(TMPS)(CN)(OH) under the selected reaction conditions. Both Fe(III)(TMPS)(CN)(H(2)O) and Fe(III)(TMPS)(CN)(2) bind nitric oxide (NO) to form the same nitrosyl complex, namely, Fe(II)(TMPS)(CN)(NO(+)). Kinetic studies indicate that nitrosylation of Fe(III)(TMPS)(CN)(2) follows a limiting dissociative mechanism that is supported by the independence of the observed rate constant on [NO] at an appropriately high excess of NO, and the positive values of both the activation parameters ΔS(?) and ΔV(?) found for the reaction under such conditions. The relatively small first-order rate constant for NO binding, namely, (1.54 ± 0.01) × 10(-2) s(-1), correlates with the rate constant for CN(-) release from the Fe(III)(TMPS)(CN)(2) complex, namely, (1.3 ± 0.2) × 10(-2) s(-1) at 20 °C, and supports the proposed nitrosylation mechanism. 相似文献
75.
Waldemar Iwanek Alicja Wzorek Zdzisława Nowakowska Grzegorz Schroeder 《Monatshefte für Chemie / Chemical Monthly》2009,140(3):359-364
Abstract Synthesis of chelates from selected l-amino acids and triethylborane, and the mass spectra of the chelates, are described. Conditions for forming dimers between
the chelates and the sodium ion are discussed, and structures are proposed for the dimers.
Graphical abstract
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76.
77.
Agnieszka Październiok-Holewa Alicja Walęcka-Kurczyk Szymon Musioł Sebastian Stecko 《Tetrahedron》2019,75(6):732-742
A catalyst-free reaction of 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates with silyl enolates was developed to prepare β-amino carbonyl compounds. The reported method is a useful approach for the preparation of N-protected β-amino esters as well as N-protected β-amino ketones. The starting 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates are readily available from N-protected α-amino acids. Therefore, the presented approach can be considered a new method for the α-homologation of N-protected α-amino acids to prepare β-amino acid derivatives. 相似文献
78.
79.
Alicja M. Kirkien Robert J. Shine Jack R. Plimmer 《Journal of mass spectrometry : JMS》1973,7(2):233-239
The mass spectra of five selenoureas and two selenothiocarbamic esters are reported and discussed. Fragmentation modes are compared with those reported for the ureas, thioureas, carbamates and thiocarbamates. 相似文献
80.
Piotr Kutrowski Dominika Sukowska Lucjan Chmielarz Piotr Olszewski Alicja Rafalska-asocha Roman Dziembaj 《Reaction Kinetics and Catalysis Letters》2005,85(2):383-390
Summary Mg-Al hydrotalcite-derived oxides with a varying Mg/Al molar ratio, ranging from 2.6 to 3.2, were rehydrated in the vapor phase at different temperatures (20-90°C). The catalytic performance of the materials obtained was studied in the aldol condensation of acetone. The initial activity of the rehydrated catalysts depended strongly on the Mg/Al molar ratio and the activation temperature. It was found that the re-arrangement of active sites, leading to the reconstruction of hydrotalcite-like phase, occurred during the catalytic test. 相似文献