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1.
Reaction of acetylene dicarboxaldehyde monoacetal with substituted Meldrum’s acid leads good yields in 2-pyranones-4-carboxaldehydes substituted in position 3. 相似文献
2.
Matthias GehreTobias Kluth Antti LipponenBangti Jin Aku SeppänenJari P. Kaipio Peter Maass 《Journal of Computational and Applied Mathematics》2012,236(8):2126-2136
We investigate the potential of sparsity constraints in the electrical impedance tomography (EIT) inverse problem of inferring the distributed conductivity based on boundary potential measurements. In sparsity reconstruction, inhomogeneities of the conductivity are a priori assumed to be sparse with respect to a certain basis. This prior information is incorporated into a Tikhonov-type functional by including a sparsity-promoting ?1-penalty term. The functional is minimized with an iterative soft shrinkage-type algorithm. In this paper, the feasibility of the sparsity reconstruction approach is evaluated by experimental data from water tank measurements. The reconstructions are computed both with sparsity constraints and with a more conventional smoothness regularization approach. The results verify that the adoption of ?1-type constraints can enhance the quality of EIT reconstructions: in most of the test cases the reconstructions with sparsity constraints are both qualitatively and quantitatively more feasible than that with the smoothness constraint. 相似文献
3.
Rufine Akué-Gédu 《Tetrahedron letters》2005,46(11):1947
In order to succeed in the acidolysis step of the synthesis (1,1,4,4-tetramethoxybut-2-yne 3b yielding 4-dimethoxybut-2-ynal 2b) it is necessary to use undried commercial 95-97% formic acid. 相似文献
4.
Rufine Akué-Gédu Daniel Couturier Jean-Pierre Hénichart Benoît Rigo Gerard Sanz Luc Van Hijfte Anne Bourry 《Tetrahedron》2012,68(27-28):5644-5654
The synthesis of new condensed indolizinediones derived from pyroglutamic acid is described. The Semmler–Wolff transposition of the oxime of these ketones leads to fused dihydro-1,5-naphthyridinones. Easy introduction of side amino chains indicates that potential DNA-intercalating heterocyclic systems fused on 1,5-naphthyridine nucleus could be obtained in these series. 相似文献
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Epunctanone,a New Benzophenone,and Further Secondary Metabolites from Garcinia epunctata Stapf (Guttiferae) 下载免费PDF全文
Ghislain W. Fotso Aku N. Ntumy Eliette Ngachussi Mthandazo Dube Renameditswe Mapitse Gilbert D. W. F. Kapche Kerstin Andrae‐Marobela Bonaventure T. Ngadjui Berhanu M. Abegaz 《Helvetica chimica acta》2014,97(7):957-964
A new polyprenylated benzophenone, named epunctanone ( 1 ), was isolated from the stem bark of Garcinia epunctata Stapf , together with eight known compounds, 7‐epiisogarcinol ( 2 ), 2,6‐dimethoxy‐p‐benzoquinone ( 3 ), friedelin ( 4 ), lupeol ( 5 ), 16β‐hydroxylupeol ( 6 ), betulin ( 7 ), stigmasterol ( 8 ), and rheediaxanthone A ( 9 ). The structure of epunctanone ( 1 ) was established by detailed analysis of its spectroscopic data, especially 1D‐ and 2D‐NMR, and HR‐MS data. All these compounds were evaluated for their antimicrobial and anti‐protozoan activities. They were also assayed to determine if any of the compounds were nonpeptide agonist ligands for nematodal G‐protein‐coupled receptors, which would be an indication of potential antinematodal activity. Among the isolated compounds, 7‐epiisogarcinol ( 2 ) was the most active against Candida albicans. 相似文献
7.
Anne Bourry Rufine Aku‐Gdu Benoit Rigo Jean‐Pierre Hnichart Grard Sanz Daniel Couturier 《Journal of heterocyclic chemistry》2003,40(6):989-993
Low solubility of the aromatic aldehyde in a water/ethanol medium can prevent the sodium borohydride reductive alkylation of the sodium salt of glutamic acid. In that case, the reductive alkylation can be realized in methanol by using a triethylammonium salt. The uses of 2 molar equivalent of triethylammonium salt of glutamic acid for one molar equivalent of aldehyde strongly raise the yields. Cyclization of the N‐substituted glutamic acids obtained gives then N‐arylmethyl pyroglutamic acids in good yields. 相似文献
8.
Vilma Kaškonienė Ieva Akuņeca Mantas Stankevičius Ona Ragažinskienė Violeta Bartkuvienė 《Natural product research》2016,30(12):1373-1381
Since biological activity of medicinal plants is dependent on cultivation area, climatic conditions, developmental stage, genetic modifications and other factors, it is important to study flora present in different growing sites and geographical zones. This study was focused on screening of antioxidant activity of C. angustifolium harvested in six different locations in Lithuania. The total contents of phenolic compounds, flavonoids and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity were evaluated by spectrophotometric methods. A correlation between radical scavenging activity and total phenolic compounds content was observed (correlation coefficient 0.98). HPLC with online post-column DPPH radical scavenging reaction detection was used for the separation of extracts. Oenothein B, rutin and one unidentified compound were predominant. Volatile compounds were analysed using solid-phase microextraction coupled with gas chromatography–mass spectrometry. Based on the analysis of volatiles, all samples were classified into two chemotypes: (I) with predominant α- and β-caryophyllenes and (II) with predominant anethole. 相似文献
9.
Comparative analysis of radical scavenging and antioxidant activities of phenolic compounds present in everyday use spice plants was carried out by means of spectrophotometric and chromatographic methods. Six spice plant samples, namely onion (Allium cepa), parsley (Petroselinum crispum) roots and leaves, celery (Apium graveolens) roots and leaves and leaves of dill (Anethum graveolens) were analyzed. Total amount of phenolic compounds and radical scavenging activity (RSA) was the highest in celery leaves and dill extracts and was the lowest in celery roots. Comparing commonly used spectrophotometric analysis of 2,2-diphenyl-1-picrylhydrazyl (DPPH) RSA of extracts with the results obtained using reversed-phase chromatographic separation with on-line post-column radical scavenging reaction detection, good correlation was obtained (R(2)=0.848). Studies using HPLC system with electrochemical detector showed that bioactive phytochemicals can be separated and antioxidant activities of individual compounds evaluated without the need of a complex HPLC system with reaction detector. The results obtained using electrochemical detection correlate with the RSA assayed using spectrophotometric method (R(2)=0.893). 相似文献
10.
Kaisa Helttunen Riia Annala Aku Suhonen Juho Iloniemi Elina Kalenius Gemma Aragay Pablo Ballester Heikki M. Tuononen Maija Nissinen 《化学:亚洲杂志》2019,14(5):647-654
The anion‐binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1H NMR spectra of the foldamers in [D6]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the release of ordered solvent molecules solvating the free foldamer and the anion to the bulk solution upon complex formation. The introduction of electron‐withdrawing substituents in foldamers 2 and 3 had only a slight effect on the thermodynamic constants for chloride binding compared to the parent receptor. Remarkably, the binding of chloride to foldamer 3 not only produced the expected 1:1 complex but also open aggregates with 1:2 (host:anion) stoichiometry. 相似文献