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41.
In a route towards enantiomerically enriched 1-(β-hydroxypropyl)indoles, which are potentially useful building blocks for high value-added chemicals synthesis, a kinetic resolution approach by means of lipase-catalyzed enantioselective acylation as well as hydrolysis/methanolysis has been elaborated for the first time. The enzymatic resolution of chiral N-substituted indole-based sec-alcohols was successfully accomplished, yielding both enantiomeric forms of the employed derivatives with up to >99% enantiomeric purity via an enantioselective transesterification under mild reaction conditions. The most selective resolutions were obtained using fungal (CAL-B and TLL) and bacterial (PFL and BCL) lipases and vinyl acetate as the acyl?group donor. The synthetic protocol described herein is very simple, user-friendly and efficient, thus paving the way for future access towards more complex compounds of this type. The absolute configurations of novel enantiomeric derivatives, and thus stereoselectivity of the described enzymatic reactions were confirmed by application of CDA-based NMR methodology and single-crystal X-ray diffraction analysis. 相似文献
42.
43.
In the paper, the results of investigation concerning the influence of 0.3% addition of hydroxypropyl methylcellulose (MC) of 40 and 70 Pa s viscosity on the hydration process of main clinker phases C3S and C3A are presented. The course of hydration is documented using microcalorimetry, and formed phases were identified by XRD. The research indicated that methylcellulose inhibited the hydration process of clinker phases, analysed both, separately and in their mixture. Moreover, it was found that the presence of MC admixture also led to the reduction in calcium sulphate dihydrate reactivity in the system. 相似文献
44.
45.
Marcin Drag Jolanta Grembecka Paweł Kafarski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1591-1595
The design, stereo-, and enantioselective synthesis and activity prediction of aminophosphonic acids as new leucine aminopeptidase inhibitors will be discussed. 相似文献
46.
Maciej Makowski Krzysztof Pawełczak Paweł Kafarski Jolanta M. Dzik Barbara Gołos Małgorzata Balinska 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1639-1651
The synthesis of six analogues of the potent thymidylate synthase (TS) inhibitor N -[4-[ N -[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinoyl)-methyl]- N -prop-2-ynylamino]benzoyl]- L -glutamic acid 2 is described in which the glutamic acid residue has been replaced by DL -aminophosphonic acids. New antifolates were tested as inhibitors of TS isolated from mouse L1210 leukemic cells as well as inhibitors of growth mouse leukemic L5178Y cells. In general these modifications result in compounds that are considerably less potent than 2 as TS inhibitors with K i 's 0.17-1.10 w M. Very poor solubility in water limited their proper assay of growth cells inhibition. 相似文献
47.
Barium cerate doped by trivalent rare earth metal ions is a potentially huge component of materials for electrochemical industry due to its high protonic conductivity. However, the poor chemical stability especially in the presence of CO2, SO2 or H2O, resulting in decreasing the mechanical durability of obtained materials, limits their possible applications. The new approach towards stable ceramic protonic conductors with high electrical conductivity is presented. Thermal stability of yttrium doped (10 mol%) of BaCeO3 was enhanced by forming the composite material BaCe0.9Y0.1O3–BaWO4 (10 mol% of BaWO4). The synthesis was performed by solid-state reaction method. The detailed study of thermal decomposition of starting powders mixture was performed using thermogravimetry and differential thermal analysis (TG/DTA) techniques combined with Evolved Gas Analysis (EGA—mass spectrometry). Structure, phase composition and microstructure together with thermal stability of sintered materials were determined. The exposition tests were performed to characterise the stability of composites in carbon dioxide and water vapour-rich atmospheres. The samples were exposed to atmosphere containing CO2/H2O (7 % of CO2 in air, 100 % RH) at temperature of 25 °C for 300 h. Thermal analysis supplied with mass spectrometry was applied to analyse the materials after the test. The results of this experiment showed better chemical resistance of composite material—BaCe0.9Y0.1O3 with 10 mol% of BaWO4 compared to single phase material. 相似文献
48.
Dynamic mechanical analysis was conducted on specimens prepared from cyanate ester (CE) and epoxy (EP) resins cured together at various mass compositions. Increase of amount of epoxy resin in composition was shown to have a disadvantageous effect on glass transition temperature (T g). It was shown that post-curing procedure was needed to produce a polymer matrix with a single glass transition relaxation, but increase in post-cure temperature up to 250 °C resulted in slight reduction in T g for epoxy/cyanate copolymers. TG results proved that the presence of epoxy resin reduces thermal stability of the cyanate/epoxy materials. The neat CE and EP/CE systems containing 30 wt% of epoxy resin were modified using epoxy-terminated butadiene–acrylonitrile rubber (ETBN) and polysiloxane core–shell elastomer (PS). The scanning electron microscopy (SEM) results showed the existence of second phase of ETBN and PS modifiers. Only in the case of EP/CE composition modified with ETBN, well-dispersed second phase domains were observed. Analysis of SEM images for other CE- and EP/CE-modified systems revealed the formation of spherical aggregates. 相似文献
49.
Katarzyna Bielicka‐Daszkiewicz Adam Voelkel Danuta Rusińska‐Roszak Paweł K. Zarzycki 《Journal of separation science》2013,36(6):1104-1111
SPE method is a very popular technique, and is commonly used for the prepurification, concentration, and isolation of different organic compounds from variable matrices. In this work, the optimization of SPE process was carried out. The breakthrough volume of solid sorbents based on octadecylsilane was determined and three methods were compared: (1) calculation one – the breakthrough volume was calculated using retention factor k determined with micro‐TLC method, frontal analysis – (2) breakthrough volume was determined as volume of whole elution peak, and (3) breakthrough volume was determined as the center of peak gravity. For calculation method, the k values of key estrogens and progestogens were derived from the micro‐TLC experiment reported previously. By combining these three methods, we can point the start of elution, the maximum concentration of analyte in eluate, and the whole eluent volume, which is necessary to achieve an appropriate selectivity and high extraction recovery. Proposed calculation method allows to estimate the beginning of the steroid peak, when the analyte appears in the eluate flowing from the sorbent. Such observation advances the SPE optimization protocol that was described before and was based on the correlation between raw kSPE and kmicro‐TLC data. 相似文献
50.
Paweł Szymański Robert Skibiński Małgorzata Liszka Izabela Jargieło Elżbieta Mikiciuk-Olasik Łukasz Komsta 《Central European Journal of Chemistry》2013,11(6):927-934
The lipophilicity of thirty-two novel acetylcholinesterase (AChE) inhibitors — 1,2,3,4-tetrahydroacridine and 2,3-dihydro-1H-cyclopenta[b]quinoline derivatives was studied by thin layer chromatography. The analyzed compounds were chromatographed on RP-18, RP-8, RP-2, CN and NH2 stationary phases with dioxane — citric buffer pH 3.0 binary mobile phases containing different proportions of dioxane. RM values for pure water were extrapolated from the linear Soczewiński-Wachtmeister equation and six compounds with known literature log P values were used as reference calibration data set for computation of experimental log P values. The obtained results were compared with computationally calculated partition coefficients values (AlogPs, AClogP, AlogP, MlogP, KOWWIN, XlogP2, XlogP3) by PCA and significant differences between them were observed. 相似文献