A new route to 3,4-disubstituted piperidines was developed using chiral 1,4-dihydropyridines as key intermediates, the synthetic utility of which was demonstrated by formal synthesis of (−)-paroxetine and (+)-femoxetine. 相似文献
We study Stanley decompositions and show that Stanley’s conjecture on Stanley decompositions implies his conjecture on partitionable
Cohen–Macaulay simplicial complexes. We also prove these conjectures for all Cohen–Macaulay monomial ideals of codimension
2 and all Gorenstein monomial ideals of codimension 3.
Dedicated to Takayuki Hibi on the occasion of his fiftieth birthday. 相似文献
Green methods using biological extracts, in particular plant-based solutions, have shown great potential for silver nanoparticle synthesis. A microwave-assisted single-step phytosynthesis of silver nanoparticles is described in the present study. The aqueous extract obtained from the Rosa santana (rose) petals was used for the first time in the synthesis. The synthesized nanoparticles obtained after optimized microwave conditions for time and temperature were analyzed by ultraviolet–visible spectroscopy (UV–Vis), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Zeta-size analysis. The results obtained from the characterization studies showed that the synthesized nanoparticles were nearly spherical in shape with sizes from 6.52?nm to 25.24?nm with an average particle size of 14.48?nm with a face-centered cubic structure. The antibacterial activities of the synthesized nanoparticles were evaluated and revealed that the silver nanoparticles displayed good inhibition against both Gram-negative and Gram-positive bacteria. Also, the cytotoxic effect of the silver nanoparticles on a mouse fibroblast cell line (L929) was studied by a cell viability assay. The results showed that phytosynthesized silver nanoparticles were nontoxic to the healthy normal cell line at all tested concentrations. 相似文献
Based on the structural elements of bioactive 3-substituted indoles, a new series of indole–thiosemicarbazone hybrid derivatives were designed, synthesized, and well-characterized using different spectral techniques. The intended scaffolds were screened for their in vitro anti-proliferative activities against breast cancer (MCF-7), lung cancer (A-549), and liver cancer (Hep-G2) cell lines, as well as their anti-oxidant properties. Cytotoxicity studies revealed that compound 6n was the most potent, at least threefold more potent than the commercially available reference drug etoposide, against A-549. In addition, morphological analysis by the acridine orange/ethidium bromide double staining test and flow cytometry analysis confirmed induction of apoptosis in the A-549 cells by compound 6n. In order to validate the experimental results, molecular studies were performed to achieve the possible binding interactions of the most potent compound (6n) and colchicine with tubulin as well as ANP with ATPase domain of topoisomerase IIα active sites. Moreover, the radical scavenging potential of the final derivatives was found to be excellent with the range of 0.015–0.630 µM, comparable to the standard ascorbic acid (0.655 µM).
We give a new characterization for prime filtrations of an R-module M in terms of primary decomposition of the zero submodule of M. Using this characterization we prove that some classes of monomial ideals like generic and cogeneric monomial ideals are clean, pretty clean, or almost clean. 相似文献
Asymmetric cyanine dyes bind to the minor groove of double stranded DNA (dsDNA) owing to their crescent configuration; therefore,
these dyes are widely used as a dsDNA probes. BOXTO-MEE is derived from BOXTO by adding the polar methoxyethoxyethyl tail
in order to increase solubility, dissociation rate kinetics, and stability. As a result, BOXTO-MEE showed significant reduction
in nonspecific amplification (primer dimers) without significant effect on target sequence amplification, PCR efficiency,
and standard curve correlation coefficient. BETIBO is another example of an asymmetric cyanine dye that can binds to dsDNA
but is less efficient than BOXTO-MEE for use in real-time PCR. Statistical analysis of reproducibility results shows that
BETIBO is not strong enough to be used for quantifying low nucleic acid quantities. Statistical analysis for BOXTO-MEE results
shows that there is no significant difference between the efficiency and correlation coefficient achieved by BOXTO-MEE and
SYBR Green I, but a significant difference in the dynamic range is observed because BOXTO-MEE has a wider dynamic range. BOXTO-MEE
stock solution was stable at −20 °C for more than 1 year and 40 μM solution was stable for 45 days (at least) at 4 °C. 相似文献
A carbon‐paste electrode modified with 2,7‐bis(ferrocenyl ethyl)fluoren‐9‐one and carbon nanotubes was used for the sensitive voltammetric determination of levodopa (LD). The electrochemical response characteristics of the modified electrode toward LD, uric acid (UA) and folic acid (FA) were investigated. The results showed an efficient catalytic activity of the electrode for the electrooxidation of LD, which leads to lowering its overpotential by more than 320 mV. The modified electrode exhibits an efficient electron mediating behavior together with well‐separated oxidation peaks for LD, UA and FA. Also, the modified electrode was used for determination of LD in some real samples. 相似文献
The thermo-oxidative stability of acetic acid lignin-containing polyurethane (LPU) that contains cross-linking agents, such
as 1-aminopropyltriethoxy-silane (APTS) and/or trimethylolpropane (TMP) was investigated based on the thermogravimetric analysis
(TGA) method, their kinetic parameters in the thermo-oxidative process was determined. FT-IR certified the occurrence of interaction
between lignin and polyurethane (PU). It was found that continuous membrane can be formed when lignin concentration was 43.3%,
but rupture took place when it increased to 50%. When the degradation was performed in nitrogen, TG and dynamic differential
thermogravimetry (DTG) results demonstrated that the PU underwent three stages of degradation while the LPU involved one main
degradation stage with a shoulder, and the degradation stability increased with the increase in the lignin concentration and
PEG length. It was also found that the addition of a cross-linking agent is beneficial to the improvement of thermal stability
and, in particular, APTS gave the best thermal stability for the LPU produced, among the cross-linking agents tested. Furthermore,
LPU exhibited multistage degradation process in air and displayed higher thermo-oxidative stability than PU. At the same time,
the kinetic study showed that LPU modified with APTS exhibited higher activation energy than LPU modified with TMP. And the
maximum activation energy was found for the sample modified with the simultaneous addition of APTS and TMP. 相似文献
In the present paper, a sensitive, fast and suitable method for the calculation of pK(a) values of fluorescein is proposed. The effects of sodium dodecyl sulfate (SDS) and Triton X-100 (TX-100) as a surface-active agent on the acidic and basic forms, and the spectral properties of fluorescein were studied by the spectrophotometric method. The study was performed in sub-micelle surfactant concentration, and absorption spectra at 300-550 nm intervals were recorded. Stepwise acidity constants of fluorescein at pH range 1.50-10.00 and at constant ionic strength 0.1M and 25 degrees C were determined using DATAN program using pH-spectrophotometric titration data. The method is efficient, however the component spectra showed intensive overlapping. The calculated acidity constants of fluorescein in water at ionic strength 0.1 are pK(a1)=2.20, pK(a2)=4.30 and pK(a3)=6.43. The acidity constants of the dye in ethanol-water solution were studied by the same procedure. Effect of surfactants and ethanol on acidity constants and pure spectrum of each component are also discussed. 相似文献
The electrocatalytic reduction of nitrite has been studied by poly(ortho‐toluidine) films modified carbon paste electrode (P‐OT/MCPE). Cyclic voltammetry and chronoamperometry techniques were used to investigate the suitability of poly(ortho‐toluidine) as a mediator for the electrocatalytic nitrite reduction in aqueous solution with various pH. Results showed that pH 0.00 is the most suitable for this purpose. In the optimum pH, the reduction of nitrite occurs at a potential about 600 mV more positive than unmodified carbon paste electrode. The catalytic reaction rate constant, (kh), was calculated 8.68×102 M?1 s?1 by the data of chronoamperometry. The catalytic reduction peak current was linearly dependent on the nitrite concentration and the linearity range obtained was 5.00×10?4 M–1.90×10?2 M. Detection limit has been found to be 3.38×10?4 M (2σ). This method has been successfully employed for quantification of nitrite in real sample. 相似文献