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排序方式: 共有624条查询结果,搜索用时 140 毫秒
51.
52.
Erika N. Daley Christopher M. Vogels Dr. Stephen J. Geier Dr. Andreas Decken Dr. Simon Doherty Prof. Dr. Stephen A. Westcott 《Angewandte Chemie (International ed. in English)》2015,54(7):2121-2125
The synthesis of phosphinoboronate esters containing a single P? B bond is reported, together with preliminary reactivity studies towards a range of organic substrates. These compounds add readily to aldehydes, ketones, aldimines, and α,β‐unsaturated enones to give primarily the corresponding 1,2‐addition products containing a new P? C bond. The first examples of transition‐metal‐catalyzed phosphinoborations of C‐C multiple bonds in which P? C and B? C bonds are formed in a single step are also disclosed; allenes react by a highly regioselective 1,2‐addition whereas terminal alkynes undergo a formal 1,1‐addition. 相似文献
53.
György Keglevich Alajos Grün Erika Bálint Nóra Zsuzsa Kiss Péter Bagi László Tőke 《Structural chemistry》2017,28(2):431-443
Application of the microwave (MW) technique offers many advantages in organophosphorus syntheses. Reluctant reactions may take place on MW irradiation. In most cases, MWs make the reactions more efficient in respect of rate, selectivity and yield. The benefits are shown via representative examples. MW irradiation may replace a catalyst, or simplify catalytic systems. The synthesis of catalysts incorporating heterocyclic P-ligands is also discussed. Where it was relevant, structural chemical details were also provided. 相似文献
54.
55.
La Ferla B Airoldi C Zona C Orsato A Cardona F Merlo S Sironi E D'Orazio G Nicotra F 《Natural product reports》2011,28(3):630-648
Cancer is one of the major causes of death worldwide. As a consequence, many different therapeutic approaches, including the use of glycosides as anticancer agents, have been developed. Various glycosylated natural products exhibit high activity against a variety of microbes and human tumors. In this review we classify glycosides according to the nature of their aglycone (non-saccharidic) part. Among them, we describe anthracyclines, aureolic acids, enediyne antibiotics, macrolide and glycopeptides presenting different strengths and mechanisms of action against human cancers. In some cases, the glycosidic residue is crucial for their activity, such as in anthracycline, aureolic acid and enediyne antibiotics; in other cases, Nature has exploited glycosylation to improve solubility or pharmacokinetic properties, as in the glycopeptides. In this review we focus our attention on natural glycoconjugates with anticancer properties. The structure of several of the carbohydrate moieties found in these conjugates and their role are described. The structure–activity relationship of some of these compounds, together with the structural features of their interaction with the biological targets, are also reported. Taken together, all this information is useful for the design of new potential anti-tumor drugs. 相似文献
56.
Izumi E Ueda-Nakamura T Dias Filho BP Veiga Júnior VF Nakamura CV 《Natural product reports》2011,28(4):809-823
Here, we review studies that have investigated the activity of plant-derived compounds against Trypanosoma cruzi, the etiologic agent of Chagas’ disease. In the last decade, more than 300 species belonging to almost 100 families have been evaluated for activity, and here we describe the compounds isolated; 85 references are cited. 相似文献
57.
Ramos EL Mata-Gómez MA Rodríguez-Durán LV Belmares RE Rodríguez-Herrera R Aguilar CN 《Applied biochemistry and biotechnology》2011,165(5-6):1141-1151
Tannase is an inducible enzyme with important applications in the food and pharmaceutical industries. This enzyme was produced by the fungus Aspergillus niger GH1 under solid-state fermentation using polyurethane foam as solid support and tannic acid as sole carbon source and tannase inducer. Physicochemical properties of A. niger tannase were characterized, and the kinetic and thermodynamics parameters on methyl gallate hydrolysis were evaluated. The enzyme was stable in a pH range of 2-8 and a functional temperature range of 25-65 °C. The highest k(cat) value was 2,611.10 s(-1) at 65 °C. Tannase had more affinity for methyl gallate at 45 °C with a K(M) value of 1.82 mM and an efficiency of hydrolysis (k(cat)/K(M)) of 330.01 s(-1) mM(-1). The lowest E(a) value was found to be 21.38 kJ/mol at 4.4 mM of methyl gallate. The lowest free energy of Gibbs (ΔG) and enthalpy (ΔH) were found to be 64.86 and 18.56 kJ/mol, respectively. Entropy (ΔS) was -0.22 kJ/mol K. Results suggest that the A. niger GH1 tannase is an attractive enzyme for industrial applications due its catalytic and thermodynamical properties. 相似文献
58.
Demesa Balderrama G Meneses EP Hernández Orihuela L Villa Hernández O Castro Franco R Pando Robles V Ferreira Batista CV 《Rapid communications in mass spectrometry : RCM》2011,25(8):1017-1027
Immobilized metal ion affinity chromatography (IMAC) has been widely used for the enrichment of phosphopeptides, whereas no report exists describing the use of IMAC columns for the enrichment of sulfopeptides. In this study, we used IMAC-Ga microcolumns for the enrichment of sulfopeptides from a complex mixture of peptides, extracted from skin secretions of the Pachymedusa dacnicolor frog. The enriched fraction obtained by IMAC-Ga was analyzed by liquid chromatograpy/electrospray ionization mass spectrometry (LC/ESI-MS) in an Orbitrap XL and by matrix-assisted laser desorption/ionization time-of-flight time-of-flight (MALDI-TOF/TOF) in an ABI 4800 instrument. From this fraction, different sulfated and non-sulfated peptides belonging to the caerulin and bradykinin families were structurally characterized. Other interesting negatively charged groups, such as phosphate adducts of dermaseptins and pyridoxal phosphate attached to a protease inhibitor, were also characterized. Unexpectedly, some dermaseptin antimicrobial peptides were also enriched by IMAC-Ga and a Sauvatine-like peptide was also fully sequenced. Furthermore, neutral loss of sulfated peptides and their fragmentation patterns in the gas phase were also compared using collision-induced dissociation (CID) and high-energy collision dissociation (HCD). Our present study provides evidence that IMAC-Ga enrichment is a fast, useful and promising method for high-throughput analysis of sulfated-peptides, since high-resolution mass spectrometers can be used for this purpose. 相似文献
59.
Reyes-Escogido Mde L Gonzalez-Mondragon EG Vazquez-Tzompantzi E 《Molecules (Basel, Switzerland)》2011,16(2):1253-1270
Capsaicin is a unique alkaloid found primarily in the fruit of the Capsicum genus and is what provides its spicy flavor. Generally extracted directly from fruit, high demand has driven the use of established methods to increase production through extraction and characterization. Over time these methods have improved, usually be applying existing techniques in conjunction. An increasingly wide range of potential applications has increased interest in capsaicin. Especially compelling are the promising results of medical studies showing possible beneficial effects in many diseases. Capsaicin's pungency has limited its use in clinical trials to support its biological activity. Characterization and extraction/ synthesis of non-pungent analogues is in progress. A review is made of capsaicin research focusing mainly on its production, synthesis, characterization and pharmacology, including some of its main potential clinical uses in humans. 相似文献
60.
Chatterjee D Ember E Pal U Ghosh S van Eldik R 《Dalton transactions (Cambridge, England : 2003)》2011,40(40):10473-10480
The Ru(III)(edta)/H(2)O(2) system (edta(4-) = ethylenediaminetretaacetate) was found to degrade the azo-dye Orange II at remarkably high efficiency under ambient conditions. Catalytic degradation of the dye was studied by using rapid-scan spectrophotometry as a function of [H(2)O(2)], [Orange II] and pH. Spectral analyses and kinetic data point towards a catalytic pathway involving the rapid formation of [Ru(III)(edta)(OOH)](2-) followed by the immediate subsequent degradation of Orange II prior to the conversion of [Ru(III)(edta)(OOH)](2-) to [Ru(IV)(edta)(OH)](-) and [Ru(V)(edta)(O)](-)via homolysis and heterolysis of the O-O bond, respectively. The higher oxidation state Ru(IV) and Ru(V) complexes react three orders of magnitude slower with Orange II than the Ru(III)-hydroperoxo complex. In comparison to biological oxygen transfer reactions, the Ru(edta) complexes show the reactivity order Compound 0 ? Compounds I and II. 相似文献