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961.
A comprehensive overview on methods applied for syntheses of β-amino-α-trifluoromethyl alcohols, including stereocontrolled variants, is presented. In addition, reported cases of the exploration of β-amino-α-trifluoromethyl alcohols for the preparation of trifluoromethylated peptidomimetics and other biologically active, fluorinated compounds are discussed. Attractive opportunities for their applications as organocatalysts are also presented. 相似文献
962.
Determination of catechin and epicatechin in the peel of apple varieties resistant and non-resistant to apple scab 总被引:1,自引:0,他引:1
Marek Gołębiowski Edmund Maliński Małgorzata Szankin Mariusz Marszeniuk Monika Paszkiewicz Piotr Stepnowski 《Chemical Papers》2010,64(6):729-733
Catechin and epicatechin were analysed in the peel of six apple cultivars (three resistant and three non-resistant to apple
scab). Two methods of analytical sample preparation following extraction were tested: solid phase extraction and column separation
with Sephadex LH-20 coupled to a differential refractometric detector. Prior to GC and GC-MS analyses, these compounds were
silylized. This permitted co-injection with standards and the comparison of retention values and mass spectra with those recorded
for standards. The content of catechin and epicatechin in apple peel is discussed in relation to the resistance of apple trees
to scab. 相似文献
963.
Krzysztof J. Reszka Piotr J. Bilski Bradley E. Britigan 《Photochemistry and photobiology》2010,86(4):742-746
Pseudomonas aeruginosa is a human pathogen, which causes infections of various organs, including lung, skin and eye, particularly in individuals who are immunocompromised. Pyocyanin (1-hydroxy-5-methylphenazine), a cytotoxic pigment secreted by the bacterium, is among the factors that contribute to virulence of this pathogen. We have previously shown that rose bengal and riboflavin photosensitize oxidation of pyocyanin to a product(s) with diminished reactivity and toxicity. Singlet oxygen was suggested as the major oxidant, based on the inhibitory effect of sodium azide. In the present study, we used the time resolved technique to investigate direct interaction of pyocyanin and related phenazines (1-hydroxyphenazine [1-OH-Phen], 1-methoxy-5-methylphenazine [1-MeO-PCN] and phenazine methosulfate [PMS]) with 1O2. The rate constants for the 1O2 quenching (physical + chemical) by pyocyanin and 1-OH-Phen in D2O buffer (pD ∼7.2) have been determined to be 4.8 × 108 and 6.8 × 108 M−1 s−1, respectively. 1-MeO-PCN and PMS were markedly less efficient 1O2 quenchers. Among the phenazines studied only phenazine methosulfate photogenerated 1O2 (Φ(1O2) = 0.56 in acetonitrile). Interaction of 1O2 with pyocyanin and other related phenazines produced by the bacteria may be important in determining the potential utility of photochemical/pharmacological approaches to eradicate P. aeruginosa from infected tissues. 相似文献
964.
A model of diffusive transport of benzoic acid through a liquid membrane (LM) separating two aqueous solutions, based on diffusion
layers and the assumption of a steady state, has been developed and tested using experimental results. It has been found that
a model with the apparent partition coefficient dependent on the concentration is able to describe the time dependence of
acid concentration in LM with and without a maximum on that dependence. The quality of the model fit with the single apparent
diffusion coefficient of benzoic acid is the same as the one which takes into account the diffusion of benzoic acid in different
forms (undissociated and dissociated form in aqueous phase, monomer and dimer in organic phase); however, in the second case,
the model becomes overparameterized. Assuming that the partition and diffusion coefficients are constant, the diffusion layer
model corresponds to the model of reversible consecutive reactions. Analytical solution for such case is given. Apart from
the partition equilibrium, also kinetics of partitioning was considered. It was shown that in some basic situations both cases
yield identical results. 相似文献
965.
Piotr Przybylski Marcin Kwit Krystian Pyta Radosław Pankiewicz Grzegorz Schroeder Jacek Gawroński Bogumil Brzezinski 《Tetrahedron: Asymmetry》2010,21(8):973-981
Gossypol Schiff base with (R)-(+)-2-amino-3-benzyloxy-1-propanol 1 was synthesised and resolved by HPLC method into diastereomers to study their atropisomerisation process. The spectroscopic analysis performed by one- and two-dimensional NMR, UV–vis and FT-IR methods indicated that the compound exists in solution as an enamine-oxo tautomer. The ECD measurements and TD-DFT calculations allowed us to unambiguously determine the configuration about the axially chiral biaryl moiety of 1. The conditions of the atropisomerisation processes of diastereopure gossypol Schiff bases (SAX,R)-1 and (RAX,R)-1 were determined on the basis of ECD and NMR measurements. Exposure of the diastereomers of 1 to sunlight and to the light at λ = 254 nm significantly accelerated the atropisomerisation when compared to its rate in the dark. 相似文献
966.
Simple, selective and sensitive isotachophoretic methods for the analysis of ionic liquid (IL) compartments were developed in this study. A leading electrolyte containing 10 mM L ‐histidine + 10 mM histidine hydrochloride and a terminating electrolyte containing 5 mM glutamic acid + 5 mM L ‐histidine were selected to separate nitrate(V), chlorate(V), hexafluorophosphate, dicyanimide, trifluoromethanesulfonate, phosphate(V) and bis(trifluoromethanesulfonyl)imide in anionic mode. In contrast, seven short‐chain alkylimidazolium, alkylpyrrolidinium, alkylpyridinium and non‐chromophoric tetraalkylammonium and tetraalkylphosphonium IL cations were separated with 10 mM potassium hydroxide + 10 mM acetic acid as leading electrolyte, and 10 mM β‐alanine + 10 mM acetate as terminating electrolyte. Both methods were optimized and validated with good analytical performance parameters. LOD was about 3–5 μM, and the repeatability lay in the range of 1.06–5.59%. These methods were evaluated for their applicability to the analysis of soil samples and freshwater contaminated with ILs. In light of hitherto the absence of reports on the determination of non‐chromophoric IL cations, this study delivers for the first time a universal method enabling analysis of these species. Moreover, as there is still significant lack of methodologies of IL anion analysis, the obtained results offer an interesting alternative in that matter. 相似文献
967.
The reaction of [RuHCl(CO)(PPh3)3] with 4-phenylpyrimidine gave a new ruthenium(II) complex, namely [RuHCl(CO)(PPh3)2(pyrim-4-Ph)]. The complex has been studied by IR and UV?Cvis spectroscopy and by X-ray crystallography. The molecular orbitals of the complex have been calculated by density functional theory. The spin-allowed singlet?Csinglet electronic transitions of the complex have been calculated by time-dependent DFT, and the UV?Cvis spectrum of the compound has been discussed on this basis. The emission properties of the complex were also studied. 相似文献
968.
Piotr Czop Krzysztof Mendrok Tadeusz Uhl 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(11):1541-1554
Requirements for current trains to be increasingly available have created the need to develop systems that can predict the
quality of both trains and infrastructure components. The paper presents a new approach to the detection of rail truck irregularities,
based on the measurements of bearing box acceleration during the operation of rail vehicles. The proposed procedure is based
on an inverse problem solution, estimating track irregularities from measured acceleration of the applied model of vehicle
dynamics. The simulation study of the proposed method, as well as its implementation, is presented. The method has been successfully
applied for the identification of rail irregularities on a typical Polish railroad and vehicle. 相似文献
969.
Anna Kamińska Anca M. Parrish 《Journal of Mathematical Analysis and Applications》2010,366(1):389-390
In this note we state the accurate formulas of convexity and concavity constants in Lorentz spaces, correcting the formulas from Kamińska and Parrish (2008) [2]. 相似文献
970.
A. Dittmar-Wituski A. Grudziński ?. Lademann A. Miko?ajczyk ?. Andraszyk M. Roszak 《Applied Surface Science》2010,256(15):4789-766
In this paper, we present experimental results of target current (TCS) and LEED investigation of well-oriented InSb(1 1 0) and InSb(1 1 1)-A and InSb(1 1 1)-B crystals. TCS results are interpreted in terms of very low electron diffraction (VLEED) and empty band signatures. To examine to which extent the TCS spectra reflect the bulk or surface electronic properties of InSb(1 1 0), thin layers of indium have been evaporated and the corresponding spectrum changes have been investigated. 相似文献