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41.
A series of eight N1-(β-D-ribofuranosyl)-C4-(coumarin-4′′-yl)-1,2,3-triazoles have been synthesized by Cu(I)-catalyzed click reaction of 1-azido-1-deoxy-2,3,5-tri-O-benzoyl-β-D-ribofuranose with differently substituted 4-ethynylcoumarins followed by debenzoylation of the resulted N1-(2′,3′,5′-tri-O-benzoyl-β-D-ribofuranosyl)-C4-(coumarin-4″-yl)-1,2,3-triazoles in 71 to 89% overall yields. The structures of all the synthesized compounds were established on the basis of their spectral data analysis that was further confirmed by X-ray data analysis of one of the model benzoylated compounds, i.e. N1-(2′,3′,5′-tri-O-benzoyl-β-D-ribofuranosyl)-C4-(7″-isopropoxycoumarin-4″-yl)-1,2,3-triazole. 相似文献
42.
Glycidic esters, upon isomerisation with BF3.Et2O yield α-hydroxy-β,γ-unsaturated esters. These are then reduced with LiAlH4 to vicinal diols which are converted to vinyl epoxides in two steps. 相似文献
43.
In this paper, spectral graph wavelet optimized finite difference method (SPGWOFD) has been proposed for solving Burger's equation with distinct boundary conditions. Central finite difference approach is utilized for the approximations of the differential operators and the grid on which the numerical solution is obtained is chosen with the help of spectral graph wavelet. Four test problems (with Dirichlet, Periodic, Robin and Neumann's boundary conditions) are considered and the convergence of the technique is checked. For assessing the efficiency of the developed technique, the computational time taken by the developed technique is compared to that of the finite difference method. It has been observed that developed technique is extremely efficient. 相似文献
44.
We have investigated the microstructures and magnetic properties of L10 ordered equi-atomic FePt thin films prepared by ion beam sputtering and subsequent annealing. It is observed from X-ray reflectivity
and X-ray diffraction measurements that the mixing at Fe/Pt interfaces starts to occur with annealing and leading to the FePt
alloy phase formation. The rapid increase in the coercivity values above 275°C, obtained from vibrating sample magnetometer
(VSM) measurements, confirms the formation of the ordered L10 FCT FePt phase. 相似文献
45.
We consider the dynamics of the disordered, one-dimensional, symmetric zero range process in which a particle from an occupied
site k hops to its nearest neighbor with a quenched rate w(k). These rates are chosen randomly from the probability distribution f(w) ∼ (w − c)
n
, where c is the lower cutoff. For n>0, this model is known to exhibit a phase transition in the steady state from a low density phase with a finite number of
particles at each site to a high density aggregate phase in which the site with the lowest hopping rate supports an infinite
number of particles. In the latter case, it is interesting to ask how the system locates the site with globally minimum rate.
We use an argument based on the local equilibrium, supported by Monte Carlo simulations, to describe the approach to the steady
state. We find that at large enough time, regions with a smooth density profile are described by a diffusion equation with
site-dependent rates, while the isolated points where the mass distribution is singular act as the boundaries of these regions.
Our argument implies that the relaxation time scales with the system size L as L
z with z = 2 + 1/(n + 1) for n>1 and suggests a different behavior for n<1. 相似文献
46.
47.
Simple, rapid and inexpensive one-step reverse micellar microextraction (RMME) procedures were combined with matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) for the determination of thiol-containing peptides and amino acids. In this investigation, a thiol-containing peptide (HW6) was chosen as model compound to understand the mechanism of RMME. The electrostatic interactions between the thiol-containing peptide and reverse micelles were proposed to be reason for the transfer of analytes from the aqueous phase to the organic phase. Reverse micelles were formed by the cationic surfactant, methyltrioctylammonium chloride (MTOAC). The best extraction efficiency of HW6 was obtained under the following conditions: pH 11.0, ionic strength 5.0 mM of KCl and micelle concentration 7.0 mM of MTOAC. The limits of detection (LODs) obtained for HW6 in water, urine and plasma samples were 0.15, 0.19 and 0.28 microM, respectively, with relative standard deviation (RSD) values in the range +/-8.8-10.5%. The sensitivity obtained in water by the present method was 45-fold higher than that of the conventional use of atmospheric-pressure (AP)-MALDI MS. Furthermore, the applicability of the proposed approach was extended for the determination of thiol-containing amino acids in sample solutions by using MALDI time-of-flight (TOF) MS. 相似文献
48.
We have obtained the ground state and the equilibrium geometries of Au(n) (-) and Au(n-1)Cu(-) in the size range of n=13-19. We have used first principles density functional theory within plane wave and Gaussian basis set methods. For each of the cluster we have obtained at least 100 distinct isomers. The anions of gold clusters undergo two structural transformations, the first one from flat cage to hollow cage and the second one from hollow cage to pyramidal structure. The Cu doped clusters do not show any flat cage structures as the ground state. The copper doped systems evolve from a general 3D structure to hollow cage with Cu trapped inside the cage at n=16 and then to pyramidal structure at n=19. The introduction of copper atom enhances the binding energy per atom as compared to gold cluster anions. 相似文献
49.
Sushama S. Kauthale Sunil U. Tekale Kavita M. Jadhav Rajendra P. Pawar 《Molecular diversity》2016,20(3):763-770
An ethylene glycol promoted catalyst-free practically efficient and sustainable approach has been developed for the synthesis of several benzylidene-bis-(4-hydroxycoumarin)s and 4,\(4^{\prime }\)-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s by the pseudo three-component reaction of an aldehyde with 4-hydroxycoumarin and 3-methyl-1-phenylpyrazol-5-one, respectively. Inexpensive, non-toxic, and easily available ethylene glycol used as the reaction solvent and promoter renders an efficient protocol in terms of catalyst-free reaction conditions, short reaction time, high yield, practical utility, and green approach. 相似文献
50.
Keshri Nath Tiwari Darshana Bora Garima Chauhan Deepika Yadav Kavita Sharma Ashima Thakur 《合成通讯》2016,46(7):620-625
An efficient and greener protocol for easy access to 3-susbstituted-3-hydroxy-2-oxindoles by the reaction with various substituted isatins and acetophenones is described. This protocol is widely applicable for a variety of isatins and acetophenones using water as a reaction media and 1,4-diazabicyclo[2.2.2]octane (DABCO) as catalyst with shorter reaction time and good to excellent yield of products. 相似文献