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91.
AbstractRhodium-catalyzed intermolecular [3?+?2+2] cycloaddition reactions of bis(methylenecyclopropanes) with different alkynes are described. The rhodium-catalyzed [3?+?2+2] cycloadditions resulted in the formation of functionalized 5–7–3 spirocyclic carbocycles in moderate yields with excellent regio- and chemo-selectivity. 相似文献
92.
Suruchi MahajanRakesh Kumar Mahajan 《Journal of colloid and interface science》2012,387(1):194-204
An evaluation of the interactions of phenothiazine tranquilizer drugs (promazine hydrochloride; PMZ and promethazine hydrochloride; PMT) with bile salts viz., sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous medium, investigated through different physicochemical measurements is presented in this work. The mixed micellization behavior and surface properties of the phenothiazine-bile salt systems have been analyzed by conductivity and surface tension measurements. Application of different theoretical approaches to all the phenothiazine-bile salt mixtures shows a non-ideal behavior. Further, the spectroscopic techniques such as UV-visible and steady state fluorescence have been employed to study the binding of phenothiazines with bile salts. The stoichiometric ratios, binding constants (K), and free energy change (ΔG) for the phenothiazine-bile salt complexes were estimated from the Benesi-Hildebrand (B-H) double reciprocal plots obtained by using the changes in spectral intensities of phenothiazines on addition of bile salts. The results are discussed in the light of use of bile salts as promising drug delivery agents for phenothiazines and hence improve their bioavailabilty. 相似文献
93.
A. D. Sagar M. M. Salunkhe P. P. Wadgaonkar B. D. Sarawade S. S. Mahajan 《Journal of polymer science. Part A, Polymer chemistry》1997,35(6):1077-1085
Ten new aromatic polyamides containing s-triazine rings in the main chain were synthesized by the low temperature interfacial polycondensation technique involving the reactions of each of the two s-triazine containing diacylchlorides, viz., 2,4-bis (4-chlorocarbonylphenoxy)-6-methoxy-s-triazine and 2,4-bis(3-chlorocarbonylphenoxy)-6-methoxy-s-triazine, with five aromatic diamines namely, 4,4′-bis(4-aminophenoxy)diphenyl sulfone, 4,4′-bis(3-aminophenoxy)diphenyl sulfone, 2,2-bis[4(4-aminophenoxy) phenyl] propane, 1,4 bis (4-amino-phenoxy) benzene, and 1,3-bis (4-aminophenoxy)benzene. The resulting polyamides were characterized by viscosity measurements, IR and 1H-NMR spectroscopy, solubility tests, x-ray diffraction, and thermogravimetry. The polyamides had inherent viscosities in the range of 0.16–1.06 dL/g in N,N-dimethylacetamide at 30°C. Most of the s-triazine containing polyamides dissolved readily at room temperature in polar solvents. Except for the polyamide PA-2, the polyamides did not lose weight below 350°C under a nitrogen atmosphere. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1077–1085, 1997 相似文献
94.
Bobroff J Alloul H Ouazi S Mendels P Mahajan A Blanchard N Collin G Guillen V Marucco JF 《Physical review letters》2002,89(15):157002
We use 89Y NMR in YBa(2)Cu(3)O(6+y) in order to evaluate with high sensitivity the distribution of hole content p in the CuO2 planes. For y=1 and y=0.6, this hole doping distribution is found narrow with a full width at half maximum smaller than Deltap=0.025. This rules out any large static phase separation between underdoped and optimally doped regions in contrast with the one observed by STM in Bi2212 and by NQR in LaSrCuO. This establishes that static electronic phase separation is not a generic feature of the cuprates. 相似文献
95.
Subratanath Koner Karuna Chaudhari Tapan K. Das S. Sivasanker 《Journal of molecular catalysis. A, Chemical》1999,150(1-2):295-297
The [CrIII(salen)]+ complex moiety is immobilized in MCM-41 matrix to obtain a new hybrid catalytic system; to test its activity, epoxidation of norbornene and hydroxylation reaction of 1-naphthol are carried out by using TBHP (tert-butylhydroperoxide) as oxidant. 相似文献
96.
97.
98.
Glättli A Daura X Bindschädler P Jaun B Mahajan YR Mathad RI Rueping M Seebach D van Gunsteren WF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(24):7276-7293
The influence of charged side chains on the folding-unfolding equilibrium of beta-peptides was investigated by means of molecular dynamics simulations. Four different peptides containing only negatively charged side chains, positively charged side chains, both types of charged side chains (with the ability to form stabilizing salt bridges) or no charged side chains were studied under various conditions (different simulation temperatures, starting structures and solvent environment). The NMR solution structure in methanol of one of the peptides (A) has already been published; the synthesis and NMR analysis of another peptide (B) is described here. The other peptides (C and D) studied herein have hitherto not been synthesized. All four peptides A-D are expected to adopt a left-handed 3(14)-helix in solution as well as in the simulations. The resulting ensembles of structures were analyzed in terms of conformational space sampled by the peptides, folding behavior, structural properties such as hydrogen bonding, side chain-side chain and side chain-backbone interactions and in terms of the level of agreement with the NMR data available for two of the peptides. It was found that the presence of charged side chains significantly slows down the folding process in methanol solution due to the stabilization of intermediate conformers with side chain-backbone interactions. In water, where the solvent competes with the solute-solute polar interactions, the folding process to the 3(14)-helix is faster in the simulations. 相似文献
99.
A new efficient reusable universal polymer support for oligonucleotide synthesis, based on a non-ammoniacal cleavable linker, is described. Twenty six cycles of oligonucleotide synthesis have been carried out without compromising the quality of the fully deprotected oligonucleotides. 相似文献
100.
Tania B. Mahajan Fiona L. Plows J. Seb Gillette Richard N. Zare Graham A. Logan 《Journal of the American Society for Mass Spectrometry》2001,12(9):989-1001
Microprobe two-step laser desorption/laser ionization mass spectrometry (μL2MS) and gas chromatography/mass spectrometry (GC/MS) were used to analyze polycyclic aromatic hydrocarbons (PAHs) in ancient terrestrial rocks. μL2MS provides an in situ analysis of very small samples, records the PAHs with no isomer information, and gives quantitative data on the degree of alkylation of a given PAH series over the complete mass range. GC/MS provides isomer separation and quantitation of PAHs in bitumen but not kerogen, and is limited by sample size. Combination of these techniques allows analysis of very small samples by μL2MS with GC/MS confirmation of isomer distributions of the solvent extractable components (bitumen). It was found that the concentration of bitumen within the rock samples affects the PAH alkylation signal for μL2MS. At low bitumen concentrations μL2MS can produce pyrolysis products from kerogen that is present; however, as bitumen concentrations increase, the PAH distribution from bitumen dominates the signal. 相似文献