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991.
M. Romero 《Tetrahedron》2009,65(10):1951-1923
Aryl halides and triflates are coupled with primary amides to give the corresponding arylamines in the presence of a palladium catalyst, a suitable ligand, and a base. The catalyst system performs well for a large number of different substrates at 100-150 °C without solvent, and with low catalyst levels (0.12 mol % Pd). Nicotinamide might be useful as a nitrogen source in the Pd-catalyzed amination reaction. 相似文献
992.
993.
Urias-Orona V Huerta-Oros J Carvajal-Millán E Lizardi-Mendoza J Rascón-Chu A Gardea AA 《Molecules (Basel, Switzerland)》2010,15(10):6948-6955
A pectin (CAP) was extracted from the husk of Cicer arietinum L. Monosaccharide analysis of CAP revealed the dominance of galacturonic acid and smaller amounts of galactose, arabinose, rhamnose, glucose, xylose and mannose. Viscosimetric analysis showed that the intrinsic viscosity ([η]) and the molecular weight (MW) of CAP were 296 mL/g and 105 kDa, respectively. The degree of esterification (DE = 10%) was determined by FTIR spectroscopy. CAP exhibited a dose-dependent free radical scavenging activity, as shown by its DPPH radical inhibition. At 1.0 mg/mL CAP exhibited a scavenging rate of 29% on DPPH radicals. The evaluation of antioxidant activity suggested that CAP had good potential for DPPH radical scavenging activity and should be explored as a novel potential antioxidant. 相似文献
994.
Various Lp form Poincaré and Opial inequalities are given for vector-valued convolution products. We apply our results to infinitesimal generators of C0-semigroups and cosine functions. Typical examples of these operators are differential operators in Lebesgue spaces. 相似文献
995.
996.
Malik G Natangelo A Charris J Pouységu L Manfredini S Cavagnat D Buffeteau T Deffieux D Quideau S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(29):9063-9074
C-glucosidic ellagitannins constitute a subclass of bioactive polyphenolic natural products with strong antioxidant properties, as well as promising antitumoral and antiviral activities that are related to their capacity to interact with both functional and structural proteins. To date, most synthetic efforts toward ellagitannins have concerned glucopyranosic species. The development of a synthetic strategy to access C-glucosidic ellagitannins, whose characteristic structural feature includes an atropoisomeric hexahydroxydiphenoyl (HHDP) or a nonahydroxyterphenoyl (NHTP) unit that is linked to an open-chain glucose core by a C-aryl glucosidic bond, is described herein. The total synthesis of the biarylic HHDP-containing 5-O-desgalloylepipunicacortein?A (1?β) was achieved by either using the natural ellagic acid bis-lactone as a precursor of the requested HHDP unit or by implementing an atroposelective intramolecular oxidative biarylic coupling to forge this HHDP unit. Both routes converged in the penultimate step of this synthesis to enable a biomimetic formation of the key C-aryl glucosidic bond in the title compound. 相似文献
997.
Hammoud L Seghiri R Benayache S Mosset P Lobstein A Chaabi M León F Brouard I Bermejo J Benayache F 《Natural product research》2012,26(3):203-208
A new flavone glucoside, apigenin 4'-(6″-methylglucuronide) (1), together with six known compounds, cirsilineol, jaceosidin, melitensin, apigenin, apigenin 7-(6″-methylglucuronide) and prunasin, were isolated from the ethanolic extract of the aerial parts of Centaurea nicaeensis All. var. walliana M. (Asteraceae) collected from Souk-Ahras, eastern Algeria. The structures were established by spectral analysis, mainly HRESI-MS, UV and 2D-NMR experiments (COSY, HSQC and HMBC). 相似文献
998.
Jorge Escorihuela María José Ba?uls Javier García Castelló Veronica Toccafondo Jaime García-Rupérez Rosa Puchades ángel Maquieira 《Analytical and bioanalytical chemistry》2012,404(10):2831-2840
Methodology for the functionalization of silicon-based materials employed for the development of photonic label-free nanobiosensors is reported. The studied functionalization based on organosilane chemistry allowed the direct attachment of biomolecules in a single step, maintaining their bioavailability. Using this immobilization approach in probe microarrays, successful specific detection of bacterial DNA is achieved, reaching hybridization sensitivities of 10?pM. The utility of the immobilization approach for the functionalization of label-free nanobiosensors based on photonic crystals and ring resonators was demonstrated using bovine serum albumin (BSA)/anti-BSA as a model system. 相似文献
999.
H. Desirena E. De la Rosa V.H. Romero J.F. Castillo L.A. Díaz-Torres J.R. Oliva 《Journal of luminescence》2012,132(2):391-397
Spectroscopic characterization of Yb3+/Er3+ codoped TeO2–R2O–ZnO–Ln2O3 glasses as a function of network modifiers (R=Li, Na and K) has been investigated. The Judd–Ofelt parameters (Ωt), quantum efficiency in near infrared (1.55 μm) and visible up-conversion (546 and 660 nm) and quality factor spectroscopy (χ) were calculated. Three up-conversion emission bands centered at 525, 546 and 660 nm were observed as maxima for glasses containing potassium. The measured lifetime of 4I13/2, 4F9/2 and 4S3/2 from Er3+ and 4F5/2 from Yb3+ levels increased when potassium (K) replaced lithium (Li) and Na. The maximum emission cross-section (ECS) for 4I13/2→4I15/2 transition of Er3+ was calculated to be 1.02×10?20 cm2 for TeO2–Li2O–ZnO–Ln2O3 glasses. The energy transfer efficiency (ET) from Yb3+ to Er3+, (4F5/2)+(4I15/2)→(4F7/2)+(4I13/2), was calculated using the measured lifetimes of Yb3+ with and without the presence of acceptor (Er3+). The maximum calculated ET was 58% for 0.25 mol% of Er3+ and 3 mol% of Yb3+ for TeO2–K2O–ZnO–Ln2O3 glass composition. 相似文献
1000.
Ledy De-la-Cruz-Martínez Constanza Duran-Becerra Martin Gonzlez-Andrade Jos C. Pez-Franco Juan Manuel Germn-Acacio Julio Espinosa-Chvez J. Martin Torres-Valencia Jaime Prez-Villanueva Juan Francisco Palacios-Espinosa Olivia Soria-Arteche Francisco Corts-Benítez 《Molecules (Basel, Switzerland)》2021,26(14)
Regulating insulin and leptin levels using a protein tyrosine phosphatase 1B (PTP1B) inhibitor is an attractive strategy to treat diabetes and obesity. Glycyrrhetinic acid (GA), a triterpenoid, may weakly inhibit this enzyme. Nonetheless, semisynthetic derivatives of GA have not been developed as PTP1B inhibitors to date. Herein we describe the synthesis and evaluation of two series of indole- and N-phenylpyrazole-GA derivatives (4a–f and 5a–f). We measured their inhibitory activity and enzyme kinetics against PTP1B using p-nitrophenylphosphate (pNPP) assay. GA derivatives bearing substituted indoles or N-phenylpyrazoles fused to their A-ring showed a 50% inhibitory concentration for PTP1B in a range from 2.5 to 10.1 µM. The trifluoromethyl derivative of indole-GA (4f) exhibited non-competitive inhibition of PTP1B as well as higher potency (IC50 = 2.5 µM) than that of positive controls ursolic acid (IC50 = 5.6 µM), claramine (IC50 = 13.7 µM) and suramin (IC50 = 4.1 µM). Finally, docking and molecular dynamics simulations provided the theoretical basis for the favorable activity of the designed compounds. 相似文献