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31.
Young-Ho Kim Vytautas Grubliauskas Orrie M. Friedman 《Journal of heterocyclic chemistry》1972,9(3):481-487
A more practical synthesis of homopteroic and homofolic acids involving condensation of 2,4,5-triamino-6(1H)pyrimidinone ( 3 ) with 1-acetoxy-4-[N-acetyl-(p-carbethoxyphenyl)amino]-2-butanone ( 7 ) is described. The biological activities of homofolic ( 1-b ) and homopteroic ( 2-b ) acids were compared and found to be identical with the activities of these products prepared by the unambiguous route. 相似文献
32.
Marius Mickevicius Zigmuntas Jonas Beresnevicius Vytautas Mickevicius Gema Mikulskiene 《Heteroatom Chemistry》2006,17(1):47-56
A series of 2‐substituted benzimidazoles, benzoxazoles were synthesized by the condensation reactions of 1‐aryl‐4‐carboxy‐2‐pyrrolidinones and aromatic ortho‐diamines or ortho‐aminophenol. Alkylation of benzimidazoles with iodoalkanes led to 1‐aryl‐4‐(1‐alkyl‐1H‐benzimidazol‐2‐yl)‐2‐pyrrolidin‐ ones or 1,3‐dialkylbenzimidazolium iodides. N‐Subs‐ tituted γ‐amino acids were prepared by the hydrolysis of 1‐aryl‐4‐(1H‐benzimidazol‐2‐yl)‐2‐pyrrolidinones in sodium hydroxide solution, followed by treatment with acetic acid. The structure of the synthesized pro‐ ducts was investigated using IR and 1H, 13C NMR spectra, MM2 molecular mechanics, and AM1 semi‐ empirical quantum mechanical methods. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:47–56, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20171 相似文献
33.
34.
Vilijandas Bagdonavičius Algis Bikelis Vytautas Kazakevičius Mikhail Nikulin 《Comptes Rendus Mathematique》2002,335(2):183-188
The paper considers degradation and failure time models with multiple failure modes. Dependence of traumatic failure intensities on the degradation level are included into the models. Non-parametric estimators of various reliability characteristics are proposed. Theorems on simultaneous asymptotic distribution of random functions characterizing degradation and intensities of traumatic events are proposed. To cite this article: V. Bagdonavi?ius et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 183–188. 相似文献
35.
Balevicius V Bariseviciute R Aidas K Svoboda I Ehrenberg H Fuess H 《Physical chemistry chemical physics : PCCP》2007,9(24):3181-3189
In this work the role of higher molecular aggregation in the proton transfer processes within hydrogen bond (H-bond) is investigated. The H-bonded complex consisting of 4-cyanopyridine (CyPy) with trichloroacetic acid (TCA) has been studied in the solutions of acetonitrile, carbon tetrachloride, chloroform and dichloroethane as solvent by FTIR spectroscopy and quantum chemical DFT calculations. In order to illustrate the effect of increasing H-bond strength FTIR investigations have also been performed on solutions of CyPy with H(2)O, acetic-, trifluoroacetic- and methanesulfonic acids. Proton states in the H-bond have been monitored using vibrational CyPy ring modes in FTIR spectra. The stabilization of the CyPy/TCA complex in its protonated form upon increasing polarity of the solvent has been evidenced. It was shown that formation of the CyPy/(TCA)(2) aggregates in the solutions favors the proton transfer process. An X-ray diffraction study has been performed on a single 1 : 2 co-crystal of pyridine/3,5-dinitrobenzoic acid. The H-bond motif found in this system exhibits the same connectivity by strong hydrogen bonds N-H(+)[dot dot dot]O(-) and O-H[dot dot dot]O as that in the CyPy/(TCA)(2) complex predicted by DFT calculation. Certain discrepancies are observed in C-H[dot dot dot]O connectivity only. The networks of H-bonds in both assemblies differ from those usually pictured for 1 : 2 base/carboxylic acid complexes in the literature. 相似文献
36.
An ultra performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS) procedure was developed for
the determination of five 5-nitroimidazoles (dimetridazole, ipronidazole, metronidazole, ronidazole and ternidazole) and three
of their metabolites (1-methyl-2-hydroxymethyl-5-nitroimidazole, 1-(2-hydroxyethyl)-2-hydroxymethyl-5-nitroimidazole and 1-methyl-2-(2′-hydroxyisopropyl)-5-nitroimidazole)
in egg matrices. Conditions for UPLC separation and electrospray ionization MS/MS in the positive ion mode were optimized.
Samples were prepared by liquid-liquid extraction with buffered aqueous 2.5% trichloroacetic acid followed by solid-phase
extraction on a Strata-X-C cartridge with reversed-phase and cation-exchange functionalities. The method’s performance was
evaluated in accordance with Commission Decision 2002/657/EC, applying the alternative matrix-comprehensive in-house validation
approach using specially designed InterVal software. The method was robust against different sample matrix and SPE cartridges,
operator change, and changes in sample extract storage. Acceptable apparent recoveries (76 to 109%) were obtained for all
analytes. The decision limits (CCα) and detection capabilities (CCα) were within the ranges of 0.19–2.62 and 0.26–4.29 μg kg−1. For all compounds the calibration curve linearity was good with correlation coefficients greater than 0.99. Fifteen eggs
and ten whole egg powder samples obtained commercially in Lithuania were analyzed by UPLC-MS/MS; none were found contaminated
by 5-nitroimidazoles or their metabolites. 相似文献
37.
Balevicius V Aidas K Tamuliene J Fuess H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(5):835-839
Moderately narrow 1H NMR signals were observed in the solid-phase obtained from pyridine-N-oxide (PyO)...HCl solutions in acetonitrile/H2O after heterogeneous phase separation. High-resolution 1H NMR spectra are compared with those of crystalline PyO...HCl and PyO...DCl. It is concluded that partially resolved peaks in 1H NMR spectra of solids are related with heterogeneity of the spin system and the presence of different mobile H-bond clusters containing PyO, HCl, DCl and water molecules. Some part of non-bonded water or HCl molecules is captured in the cavities of crystalline samples. The attribution of the 1H NMR signals was based on the density functional theory calculation of proton magnetic screening tensor of the most expected H-bond structures in the 6-311G** basis taking into account the solvent effect by the polarized continuum model. 相似文献
38.
Vytautas Getautis Giedre Sinkeviciute Albina Stanisauskaite 《Monatshefte für Chemie / Chemical Monthly》2007,45(10):477-480
A synthesis of 1,2-diphenylpyrazolidin-4-ol via direct heterocyclization of 1,2-diphenylhydrazine with 1-chloro-2,3-epoxypropane, its O-epoxypropyl-, O-ethyl-, and O-benzylderivatives are described. Novel hydrazone derivatives with pyrazolidine units were also synthesized. The compounds
were characterized by spectroscopic methods as well as elemental analyses. 相似文献
39.
Vytautas Kazakevičius 《Lithuanian Mathematical Journal》2011,51(1):3-12
We construct a class of noninjective aperiodic circle transformations. As a by-product, we establish some new properties of Mersenne numbers. 相似文献
40.
Rizzi Andrea Jensen Travis Slochower David R. Aldeghi Matteo Gapsys Vytautas Ntekoumes Dimitris Bosisio Stefano Papadourakis Michail Henriksen Niel M. de Groot Bert L. Cournia Zoe Dickson Alex Michel Julien Gilson Michael K. Shirts Michael R. Mobley David L. Chodera John D. 《Journal of computer-aided molecular design》2020,34(5):601-633
Journal of Computer-Aided Molecular Design - Approaches for computing small molecule binding free energies based on molecular simulations are now regularly being employed by academic and industry... 相似文献