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991.
Ureidopeptide‐Based Brønsted Bases: Design,Synthesis and Application to the Catalytic Enantioselective Synthesis of β‐Amino Nitriles from (Arylsulfonyl)acetonitriles 下载免费PDF全文
Dr. Saioa Diosdado Dr. Rosa López Prof. Dr. Claudio Palomo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6526-6531
The addition of cyanoalkyl moieties to imines is a very attractive method for the preparation of β‐amino nitriles. We present a highly efficient organocatalytic methodology for the stereoselective synthesis of β‐amino nitriles, in which the key to success is the use of ureidopeptide‐based Brønsted base catalysts in combination with (arylsulfonyl)acetonitriles as synthetic equivalents of the acetonitrile anion. The method gives access to a variety of β‐amino nitriles with good yields and excellent enantioselectivities, and broadens the stereoselective Mannich‐type methodologies available for their synthesis. 相似文献
992.
Reversed‐phase high‐performance liquid chromatography method with fluorescence detection to screen nitric oxide synthases inhibitors 下载免费PDF全文
Cristina Maccallini Mauro Di Matteo Alessandra Ammazzalorso Alessandra D'Angelo Barbara De Filippis Sara Di Silvestre Marialuigia Fantacuzzi Letizia Giampietro Assunta Pandolfi Rosa Amoroso 《Journal of separation science》2014,37(12):1380-1385
Nitric oxide synthase (NOS) inhibitors are potential drug candidates due to the critical role of an excessive production of nitric oxide in a range of diseases. At present, the radiometric detection of l ‐[3H]‐citrulline produced from l ‐[3H]‐arginine during the enzymatic reaction is one of the most accepted methods to assess the in vitro activity of NOS inhibitors. Here we report a fast, easy, and cheap reversed‐phase high‐performance liquid chromatography method with fluorescence detection, based on the precolumn derivatization of l ‐citrulline with o‐phthaldialdehyde/N‐acetyl cysteine, for the in vitro screening of NOS inhibitors. To evaluate enzyme inhibition by the developed method, N‐[3‐(aminomethyl)benzyl]acetamidine, a potent and selective inhibitor of inducible NOS, was used as a test compound. The half maximal inhibitory concentration obtained was comparable to that derived by the well‐established radiometric assay. 相似文献
993.
Núria Gilart Rosa Maria Marcé Peter A. G. Cormack Núria Fontanals Francesc Borrull 《Journal of separation science》2014,37(16):2225-2232
Polar vinyl monomers have been used for the synthesis of several polymer monoliths, to serve as novel coatings for stir bar sorptive extraction; the monovinyl monomers 2‐hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) monomethacrylate) (PEGMA) were copolymerized with (apolar) divinylbenzene (DVB) and/or pentaerythritol triacrylate (PETRA), both of which are cross‐linking agents. After the optimization of the most important synthesis parameters, which included the ratio between total monomers and porogen, the nature of the porogen, and the monomer ratios, inter alia, three mechanically stable, polar monolithic coatings for stir bar sorptive extraction were obtained that were based on poly(HEMA‐co‐DVB), poly(HEMA‐co‐PETRA), and poly(PEGMA‐co‐PETRA). Thereafter, and in order to evaluate the hydrophilicity of the resulting monoliths, they were applied as materials in the stir bar sorptive extraction of a group of emerging pollutants with a wide range of polarities. The results showed that both the poly(HEMA‐co‐DVB) and poly(PEGMA‐co‐PETRA) materials could be used to extract both polar and nonpolar compounds by stir bar sorptive extraction, in an effective manner. Taking into account the desired chemical and morphological properties, as well as the extraction efficiencies, the poly(PEGMA‐co‐PETRA) material seemed to be a particularly promising monolith for application as a novel coating in stir bar sorptive extraction. 相似文献
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Claudio De Rosa Finizia AuriemmaOdda Ruiz de Ballesteros Rocco Di GirolamoMartina Pepe Oreste TaralloAnna Malafronte 《European Polymer Journal》2013
A study of the thermodynamic stability and the related polymorphic transformations induced by thermal treatments of the mesomorphic form that crystallizes in stereodefective metallocene isotactic polypropylene (iPP) is presented. We show that the mesomorphic form of the more isotactic samples is stable at room temperature, whereas the mesomorphic form crystallizing in the more stereoirregular sample is unstable and crystallizes at room temperature in the crystalline α form. In any case, the mesomorphic form transforms during heating or by annealing at temperatures higher than 60–80 °C always in the α form, regardless of the stereoregularity, even in the case of stereoirregular samples generally crystallizing from the melt in the γ form. These data confirm the proposed model of structure of the mesomorphic form as small aggregates of chains in three-fold helical conformation packed with lateral correlations similar to the α form of iPP. 相似文献
997.
Valencia Dalia Lillo Rosa E. Romo Juan 《Advances in Data Analysis and Classification》2019,13(4):1083-1103
Measuring dependence is a very important tool to analyze pairs of functional data. The coefficients currently available to quantify association between two sets of curves show a non robust behavior under the presence of outliers. We propose a new robust numerical measure of association for bivariate functional data. We extend in this paper Kendall coefficient for finite dimensional observations to the functional setting. We also study its statistical properties. An extensive simulation study shows the good behavior of this new measure for different types of functional data. Moreover, we apply it to establish association for real data, including microarrays time series in genetics.
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Pedro Álvarez‐Boo José S. Casas Eduardo E. Castellano M. Delfina Couce Rosa Farto Eduardo Freijanes José Sordo 《应用有机金属化学》2007,21(1):49-53
Reaction of 3‐(2‐methoxyphenyl)‐2‐sulfanylpropenoic acid [H2(o‐mpspa)] with SnPh3OH in the presence of di‐isopropylamine resulted in the formation of the complex [HQ][SnPh3(o‐mpspa)] (where HQ = di‐isopropylammonium cation and o‐mpspa = 3‐(2‐methoxyphenyl)‐2‐sulfanylpropenoato), which was characterized by mass spectrometry and vibrational spectroscopy, as well as by 1H, 13C and 119Sn NMR spectroscopy. The single‐crystal X‐ray structural analysis of the new complex shows a trigonal‐bipyramidal coordination geometry around the Sn atom where o‐mpspa behaves as a bidentate chelating ligand. Dimeric units arise from the existence of N? H…O hydrogen bonds between the NH2 group of the di‐isopropylammonium cation and the oxygen atoms of the two neighbouring carboxylato groups. The bacteriostatic activity of the complex is also reported. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献