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151.
Gowravaram Sabitha Gajangi Chandrashekhar Kurra Yadagiri Jhillu Singh Yadav 《Tetrahedron: Asymmetry》2011,22(18-19):1729-1735
The total syntheses of the first examples of diarylheptanoid natural products (5S)-5-acetoxy-1,7-bis(4-hydroxy-3-methoxyphenyl)-3-heptanone 1, and (3S,5S)-3,5-diacetoxy-1,7-bis(4-hydroxy-3-methoxyphenyl)heptane 2 isolated from the rhizomes of Zingiber officinale were accomplished using Sharpless epoxidation and cross-metathesis reactions as the key steps. 相似文献
152.
J.S. Yadav Saibal Das J. Satyanarayana Reddy N. Thrimurtulu A.R. Prasad 《Tetrahedron letters》2010,51(31):4050-4052
The first total synthesis of (3R),(5R)-5-hydroxy-de-O-methyllasiodiplodin and its epimer is reported from malic acid. The adopted approach is highly convergent and stereoselective. The strategy utilizes syn selective reduction and ring-closing metathesis as key steps. 相似文献
153.
154.
The synthesis of C1-C12 and C13-C22 fragments of (−)-callystatin A is accomplished employing desymmetrization strategy for the creation of five chiral centres of the polypropionate fragment and application of cross-metathesis (CM) reaction for the first time for this molecule. 相似文献
155.
B.V. Subba Reddy B. Bramha Reddy K.V. Raghavendra Rao J.S. Yadav 《Tetrahedron letters》2012,53(20):2500-2503
A tandem cycloisomerization/Friedel–Crafts alkylation of indoles has been achieved in a one-pot process to produce 2,5-disubstituted furans using gallium-catalyzed sequential nucleophilic addition onto metal-activated 1-alkynyl-2,3-epoxy acetates. The reaction proceeds efficiently under mild conditions with complete regioselectivity to afford the substituted furan derivatives in good yields with high diversity. 相似文献
156.
Bianchi Type-IX viscous fluid cosmological model is investigated. To get a deterministic model, we have assumed the conditiona = b
m(m is a constant) between metric potentials andη ∞θ whereη is the coefficient of shear viscosity andθ the scalar of expansion in the model. The coefficient of bulk viscosity (ς) is taken as constant. The physical and geometrical
aspects of the model are also discussed. 相似文献
157.
Mahesh Kumar Yadav Anju Rai Anirudh Pradhan 《International Journal of Theoretical Physics》2007,46(11):2677-2687
We investigate the integrability of cosmic strings in Bianchi III space-time in presence of a bulk viscous fluid by applying
a new technique. The behavior of the model is reduced to the solution of a single second order nonlinear differential equation.
We show that this equation admits an infinite family of solutions. Some physical consequences from these results are also
discussed. 相似文献
158.
PANI/PMMA composite was synthesized by emulsion polymerization pathway and the composite thin film was obtained by vacuum evaporation. The effect of vapour chopping and varying PMMA concentration was also studied. The FTIR spectra showed that the PANI/PMMA composite thin film deposited as a short chain oligomers. Increase in transmittance and decrease in refractive index was obtained with increasing concentration of PMMA, which further increased the adhesion and decreased intrinsic stress. The vapour chopping improved its optical as well as mechanical properties and produced smoother surface morphology. Increase of PMMA made the film more amorphous and does not change its band gap. 相似文献
159.
The breakdown of statistical homogeneity and isotropy of cosmic perturbations is a generic feature of ultra-large scale structure
of the cosmos, in particular, of non-trivial cosmic topology. The statistical isotropy (SI) of the cosmic microwave background
temperature fluctuations (CMB anisotropy) is sensitive to this breakdown on the largest scales comparable to, and even beyond
the cosmic horizon. We propose a set of measures,K
l
(l = 1, 2,3,...) which for non-zero values indicate and quantify statistical isotropy violations in a CMB map. We numerically
compute the predictedK
l
spectra for CMB anisotropy in flat torus universe models. Characteristic signatures of different models in theK
l
spectrum are noted. 相似文献
160.
We study theoretically the destruction of spin nematic order due to quantum fluctuations in quasi-one-dimensional spin-1 magnets. If the nematic ordering is disordered by condensing disclinations, then quantum Berry phase effects induce dimerization in the resulting paramagnet. We develop a theory for a Landau-forbidden second order transition between the spin nematic and dimerized states found in recent numerical calculations. Numerical tests of the theory are suggested. 相似文献