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81.
The cross-coupling reaction of α-arylacetyl chlorides with triarylbismuths was studied under Pd-catalyzed conditions. The reaction was found to be facile under the established protocol and furnished high yields of α-aryl ketones in short reaction times. This work also demonstrated a facile synthesis of various regio-isomeric mono-, di- and tri-substituted α-aryl ketones in high yields. Triarylbismuths were employed as sub-stoichiometric multi-coupling organometallic nucleophiles in this coupling protocol. 相似文献
82.
Chandan Kumar Jana Dr. Stefan Grimme Prof. Dr. Armido Studer Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9078-9084
CuI‐catalyzed enantioselective nitroso‐Diels–Alder reactions (NDA reactions) of 2‐nitrosopyridine with various dienes are presented. The [CuPF6(MeCN)4]/Walphos‐CF3 catalyst system is best suited to catalyze the NDA reaction of various dienes by using 2‐nitrosopyridine as a dienophile. In most of the cases studied, cycloadducts are obtained in quantitative yield with very good to excellent enantioselectivities. Based on DFT calculations, a model to explain the stereochemical outcome of the NDA reaction is presented. Finally, an efficient short synthesis of (?)‐peracetylated conduramine A‐1 by applying the enantioselective NDA reaction as a key step is described. 相似文献
83.
Chandan K. Dubey 《Discrete Applied Mathematics》2009,157(1):149-163
An undirected graph G=(V,E) with a specific subset X⊂V is called X-critical if G and G(X), induced subgraph on X, are indecomposable but G(V−{w}) is decomposable for every w∈V−X. This is a generalization of critically indecomposable graphs studied by Schmerl and Trotter [J.H. Schmerl, W.T. Trotter, Critically indecomposable partially ordered sets, graphs, tournaments and other binary relational structures, Discrete Mathematics 113 (1993) 191-205] and Bonizzoni [P. Bonizzoni, Primitive 2-structures with the (n−2)-property, Theoretical Computer Science 132 (1994) 151-178], who deal with the case where X is empty.We present several structural results for this class of graphs and show that in every X-critical graph the vertices of V−X can be partitioned into pairs (a1,b1),(a2,b2),…,(am,bm) such that G(V−{aj1,bj1,…,ajk,bjk}) is also an X-critical graph for arbitrary set of indices {j1,…,jk}. These vertex pairs are called commutative elimination sequence. If G is an arbitrary indecomposable graph with an indecomposable induced subgraph G(X), then the above result establishes the existence of an indecomposability preserving sequence of vertex pairs (x1,y1),…,(xt,yt) such that xi,yi∈V−X. As an application of the commutative elimination sequence of an X-critical graph we present algorithms to extend a 3-coloring (similarly, 1-factor) of G(X) to entire G. 相似文献
84.
Jana C Jayamurugan G Ganapathy R Maiti PK Jayaraman N Sood AK 《The Journal of chemical physics》2006,124(20):204719
We study the structure of carboxylic acid terminated neutral poly(propyl ether imine) (PETIM) dendrimer from generations 1-6 (G1-G6) in a good solvent (water) by fully atomistic molecular dynamics (MD) simulations. We determine as a function of generation the structural properties such as radius of gyration, shape tensor, asphericity, fractal dimension, monomer density distribution, and end-group distribution functions. The sizes obtained from the MD simulations have been validated by small angle x-ray scattering experiment on dendrimer of generations 2-4 (G2-G4). A good agreement between the experimental and theoretical value of radius of gyration has been observed. We find a linear increase in radius of gyration with the generation. In contrast, Rg scales as approximately Nx with the number of monomers. We find two distinct exponents depending on the generations, x=0.47 for G1-G3 and x=0.28 for G3-G6, which reveal their nonspace filling nature. In comparison with the amine terminated poly(amidoamine) (PAMAM) dendrimer, we find that Rg of Gth generation PETIM dendrimer is nearly equal to that of (G+1)th generation of PAMAM dendrimer as observed by Maiti et al. [Macromolecules 38, 979 (2005)]. We find substantial back folding of the outer subgenerations into the interior of the dendrimer. Due to their highly flexible nature of the repeating branch units, the shape of the PETIM dendrimer deviates significantly from the spherical shape and the molecules become more and more spherical as the generation increases. The interior of the dendrimer is quite open with internal cavities available for accommodating guest molecules, suggesting the use of PETIM dendrimer for guest-host applications. We also give a quantitative measure of the number of water molecules present inside the dendrimer. 相似文献
85.
We present a semimicroscopic model of dsDNA by incorporating the directional nature of hydrogen bond to describe the force induced unzipping transition. Using exact enumeration technique, we obtain the force-temperature and the force-extension curves and compare our results with the other models of dsDNA. The model proposed by us is rich enough to describe the basic mechanism of dsDNA unzipping and predicts the existence of an "eye phase." We show oscillations in the probability distribution function during unzipping. Effects of stacking energies on the melting profile have also been studied. 相似文献
86.
We investigate the helicity-dependent generalized parton distributions (GPDs) in momentum as well as transverse position (impact) spaces for the u and d quarks in a proton when the momentum transfer in both the transverse and the longitudinal directions are nonzero. The GPDs are evaluated using the light-front wave functions of a quark–diquark model for nucleon where the wave functions are constructed by the soft-wall AdS/QCD correspondence. We also express the GPDs in the boost-invariant longitudinal position space. 相似文献
87.
M. Nuñez Portela E. A. Dijck A. Mohanty H. Bekker J. E. van den Berg G. S. Giri S. Hoekstra C. J. G. Onderwater S. Schlesser R. G. E. Timmermans O. O. Versolato L. Willmann H. W. Wilschut K. Jungmann 《Applied physics. B, Lasers and optics》2014,114(1-2):173-182
A single Ra+ ion stored in a Paul radio frequency ion trap has excellent potential for a precision measurement of the electroweak mixing angle at low momentum transfer and as the most stable optical clock. The effective transport and cooling of singly charged ions of the isotopes 209Ra to 214Ra in a gas filled radio frequency quadrupole device is reported. The absolute frequencies of the transition 7s2S1/2–7d2D3/2 at wavelength 828 nm have been determined in 212–214Ra+ with ≤19 MHz uncertainty using laser spectroscopy on small samples of ions trapped in a linear Paul trap at the online facility Trapped Radioactive Isotopes: µicrolaboratories for fundamental Physics (TRIµP) of the Kernfysisch Versneller Instituut. 相似文献
88.
Karmakar S Choudhury M Das AS Maiti A Majumdar S Mitra C 《Natural product research》2012,26(6):500-509
This study examined the efficacy of hydroalcoholic extract of dried clove buds, which is rich in phenolic compounds namely eugenol and eugenol derivatives (precursors of flavones, isoflavones and flavonoids), on different primary and secondary osteoporotic marker changes in an ovariectomised (OVX) rat model of osteoporosis. Female Wistar rats were randomly divided into three groups: sham-operated control (A), OVX (B) and OVX plus 50% hydroalcoholic extract of dried clove buds for 4 weeks (C). Results indicated that, compared to control, serum alkaline phosphatase (AP; 48.25%, p?0.01), serum tartrate-resistant acid phosphatase (TRAP; 63.48%, p?0.01), urinary calcium (14.70%, p?0.01), urinary phosphate (50.30%, p?0.01) and urinary creatinine (122.44%, p?0.01) were significantly altered in OVX rats. All these altered responses were significantly restored (AP: 27.53%, p?0.01; TRAP: 33.51%, p?0.01; calcium: 53.15%, p?0.01; phosphate: 27.49%, p?0.01; creatinine: 46.40%, p?0.01) by supplementation with hydroalcoholic extract of dried clove buds. Results of bone density, bone mineral content, bone tensile strength and histological analysis also showed similar trend of results, which supported initial observations of this study. It is proposed that hydroalcoholic extract of dried clove buds has bone-preserving efficacy against hypogonadal osteoporosis. 相似文献
89.
Sharma K Police A Kumar A Pawar GV Giri S Rajagopal S Mullangi R 《Biomedical chromatography : BMC》2012,26(7):833-838
A highly sensitive, rapid assay method was developed and validated for the estimation of lorglumide in mouse plasma using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in positive‐ion mode. The assay procedure involves extraction of lorglumide and phenacetin (internal standard, IS) from mouse plasma with simple protein precipitation. Chromatographic separation was achieved using an isocratic mobile (0.2% formic acid solution–acetonitrile, 20:80, v/v) at a flow‐rate of 0.5 mL/min on an Atlantis dC18 column maintained at 40 °C with a total run time of 4.0 min. The MS/MS ion transitions monitored were 459.2 → 158.4 for lorglumide and 180.1 → 110.1 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.42 ng/mL and the linearity range extended from 0.42 to 500 ng/mL. The intra‐ and inter‐day precisions were in the ranges of 1.47–10.9 and 3.56–7.53, respectively. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
90.
Sharma K Kandaswamy M Mithra C Meena AK Giri S Rajagopal S Mullangi R 《Biomedical chromatography : BMC》2012,26(2):247-255
A highly sensitive and specific LC-MS/MS-ESI method was developed for simultaneous quantification of albenadazole (ABZ) and ricobendazole (RBZ) in rat plasma (50 μL) using phenacetin as an internal standard (IS). Simple protein precipitation was used to extract ABZ and RBZ from rat plasma. The chromatographic resolution of ABZ, RBZ and IS was achieved with a mobile phase consisting of 5 m m ammonium acetate (pH 6) and acetonitrile (20:80, v/v) at a flow rate of 1 mL/min on a Chromolith RP-18e column. The total chromatographic run time was 3.5 min and the elution of ABZ, RBZ and IS occurred at 1.66, 1.50 and 1.59 min, respectively. A linear response function was established for the ranges of concentrations 2.01-2007 and 6.02-6020 ng/mL for ABZ and RBZ, respectively. The intra- and inter-day precision values for ABZ and RBZ met the acceptance as per FDA guidelines. ABZ and RBZ were stable in battery of stability studies, viz. bench-top, auto-sampler and freeze-thaw cycles. The developed assay was applied to a pharmacokinetic study in rats. 相似文献