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911.
A new tropane alkaloid from the leaves of Erythroxylum subsessile isolated by pH‐zone‐refining counter‐current chromatography 下载免费PDF全文
Rodrigo Alves Soares Cruz Henrique Almeida Caio Pinho Fernandes Pedro Joseph‐Nathan Leandro Rocha Gilda Guimarães Leitão 《Journal of separation science》2016,39(7):1273-1277
Tropane alkaloids are bioactive metabolites with great importance in the pharmaceutical industry and the most important class of natural products found in the Erythroxylum genus. However, these compounds are usually separated by traditional chromatographic techniques, in which the sample is progressively purified in multiple chromatographic steps, resulting in a time‐ and solvent‐consuming procedure. In this work we present the isolation of a novel alkaloid, 6β,7β‐dibenzoyloxytropan‐3α‐ol, together with the two known 3α‐benzoyloxynortropan‐6β‐ol and 3α,6β‐dibenzoyloxytropane alkaloids, directly from the crude alkaloid fraction from the leaves of Erythroxylum subsessile, by using a single run pH‐zone‐refining counter‐current chromatography method. The ethyl acetate/water (1:1, v/v) biphasic solvent system with triethylamine and HCl as retention and eluter agents, respectively, was used to isolate tropane alkaloids for the first time. The structures of the isolated alkaloids were elucidated by spectroscopic methods. 相似文献
912.
Integration of Commercial Screen‐printed Electrodes into a Voltammetric Electronic Tongue for the Analysis of Aminothiols 下载免费PDF全文
Ricardo H. P. Pedroza Núria Serrano José Manuel Díaz‐Cruz Cristina Ariño Miquel Esteban 《Electroanalysis》2016,28(7):1570-1577
A voltammetric sensor array (or electronic tongue) is developed for the simultaneous quantification of cysteine, glutathione and homocysteine without need of previous separation. It is based on the integration of three commercial screen‐printed electrodes (gold curated at high and low temperature and carbon modified with carbon nanotubes). Linear sweep voltammograms measured simultaneously by all three sensors are processed by Partial Least Squares (PLS) regression and different variables selection algorithms such as Genetic Algorithm and interval‐Partial Least Squares. The method was applied to synthetic mixtures and successfully validated, with correlation coefficients of prediction (Rp2) of 0.9542, 0.9429 and 0.9589 for cysteine, glutathione, and homocysteine respectively. 相似文献
913.
Dr. Erika A. Crane Prof. Dr. Karl Gademann 《Angewandte Chemie (International ed. in English)》2016,55(12):3882-3902
Natural products have had an immense influence on science and have directly led to the introduction of many drugs. Organic chemistry, and its unique ability to tailor natural products through synthesis, provides an extraordinary approach to unlock the full potential of natural products. In this Review, an approach based on natural product derived fragments is presented that can successfully address some of the current challenges in drug discovery. These fragments often display significantly reduced molecular weights, reduced structural complexity, a reduced number of synthetic steps, while retaining or even improving key biological parameters such as potency or selectivity. Examples from various stages of the drug development process up to the clinic are presented. In addition, this process can be leveraged by recent developments such as genome mining, antibody–drug conjugates, and computational approaches. All these concepts have the potential to identify the next generation of drug candidates inspired by natural products. 相似文献
914.
Navneet K. Gupta Dr. Anastasia Pashigreva Dr. Evgeny A. Pidko Prof. Emiel J. M. Hensen Prof. Leslaw Mleczko Dr. Stefan Roggan Dr. Erika E. Ember Prof. Johannes A. Lercher 《Angewandte Chemie (International ed. in English)》2016,55(5):1728-1732
Active sites in carbon‐catalyzed phosgene synthesis from gaseous CO and Cl2 have been identified using C60 fullerene as a model catalyst. The carbon atoms distorted from sp2 coordination in non‐planar carbon units are concluded to generate active Cl2. Experiments and density functional theory calculations indicate the formation of a surface‐bound [C60???Cl2] chlorine species with radical character as key intermediate during phosgene formation. It reacts rapidly with physisorbed CO in a two‐step Eley–Rideal‐type mechanism. 相似文献
915.
In this paper, we propose an extragradient algorithm for solving equilibrium problems on Hadamard manifolds to the case where the equilibrium bifunction is not necessarily pseudomonotone. Under mild assumptions, we establish global convergence results. We show that the multiobjective optimization problem satisfies all the hypotheses of our result of convergence, when formulated as an equilibrium problem. 相似文献
916.
Hiraoka S Okuno E Tanaka T Shiro M Shionoya M 《Journal of the American Chemical Society》2008,130(28):9089-9098
For a long-range transmission of motion between two movable parts apart from each other, transmitters that can precisely correlate these two motions should be properly incorporated into the system. However, such a motional relay is yet to be realized in artificial systems because of the lack of reliable methodologies for arranging a discrete number of motional parts. Herein, we report a correlated motion of two rotor molecules, which are coaxially arranged at a distance of 1.5 nm, through either Ag (+)- or Hg (2+)-assembled helical transmitters, leading to different frequencies of synchronized motion. A helix inversion in the transmitter was proven to strongly correlate the motions of both terminals. The X-ray analysis of the entity determined a quadruple-decker nonanuclear structure of the metal complex comprising two terminal rotor-like ligands closely attached to a central transmitter moiety. (1)H NMR analysis fully demonstrated the synchronized motion of the two rotors coaxially stacked and connected through the transmitter. Since the transmitter is composed of simple helical repeating units, the principle of helix inversion would be an efficient and widely applicable strategy for the long-range transmission of molecular motion. 相似文献
917.
Hong Phong Duong Dr. Jose Guillermo Rivera de la Cruz Dr. Ngoc-Huan Tran Jacques Louis Dr. Sandrine Zanna Dr. David Portehault Dr. Andrea Zitolo Dr. Michael Walls Dr. Deizi Vanessa Peron Dr. Moritz W. Schreiber Prof. Nicolas Menguy Prof. Marc Fontecave 《Angewandte Chemie (International ed. in English)》2023,62(49):e202310788
The need of carbon sources for the chemical industry, alternative to fossil sources, has pointed to CO2 as a possible feedstock. While CO2 electroreduction (CO2R) allows production of interesting organic compounds, it suffers from large carbon losses, mainly due to carbonate formation. This is why, quite recently, tandem CO2R, a two-step process, with first CO2R to CO using a solid oxide electrolysis cell followed by CO electroreduction (COR), has been considered, since no carbon is lost as carbonate in either step. Here we report a novel copper-based catalyst, silver-doped copper nitride, with record selectivity for formation of propanol (Faradaic efficiency: 45 %), an industrially relevant compound, from CO electroreduction in gas-fed flow cells. Selective propanol formation occurs at metallic copper atoms derived from copper nitride and is promoted by silver doping as shown experimentally and computationally. In addition, the selectivity for C2+ liquid products (Faradaic efficiency: 80 %) is among the highest reported so far. These findings open new perspectives regarding the design of catalysts for production of C3 compounds from CO2. 相似文献
918.
Busch GK Tate EW Gaffney PR Rosivatz E Woscholski R Leatherbarrow RJ 《Chemical communications (Cambridge, England)》2008,(29):3369-3371
We report an effective strategy for generating N-terminal cysteinyl proteins by proteolytic cleavage using the enzyme 3C pro, suitable for a wide range of applications via native chemical ligation. 相似文献
919.
Basile F Benito P Del Gallo P Fornasari G Gary D Rosetti V Scavetta E Tonelli D Vaccari A 《Chemical communications (Cambridge, England)》2008,(25):2917-2919
New highly conductive, active and stable Ni steam reforming catalysts were prepared through a method consisting of the calcination of a hydrotalcite-like compound electrodeposited in a single step on FeCrAlloy foams. 相似文献
920.