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51.
A rapid and efficient method for stereoselective synthesis of new substituted tetrahydro-α-carbolines using Diels-Alder reaction under microwave irradiation has been developed. Further, dehydrogenation of these adducts resulted in synthesis of new substituted α-carbolines. 相似文献
52.
53.
Jaanus Kruusma Aidan Rhodes Radhika Bhatia J. A. Gareth Williams Adam M. Benham Ritu Kataky 《Journal of solution chemistry》2007,36(4):517-529
Increasing enrichment of dimethyl sulfoxide, DMSO, in DMSO-water mixtures causes a reversal in the thermodynamic dissociation
constants, pK
as, and has a marked effect on the redox potentails of the thiolic and amino groups in cysteine and the protein disulfide isomerase
(PDI) mimic BMC, Vectrase. This paper illustrates the effect of a hydrogen-bonding environment on the ionisation and redox
properties of thiol groups in amino acids. A combination of potentiometry and Raman spectroscopy was applied to rationalise
the observations. Intracellular environments are full of hydrophobic, hydrogen-bonding environments. The results illustrate
the profound effects of the local environment on the thiol group. 相似文献
54.
He GS Lin TC Dai J Prasad PN Kannan R Dombroskie AG Vaia RA Tan LS 《The Journal of chemical physics》2004,120(11):5275-5284
Degenerate two-photon absorption (TPA) spectral properties of five AFX chromophore solutions have been studied using a single and spectrally dispersed sub-picosecond white-light continuum beam. In a specially designed optical configuration, optical pathways inside the sample solution for different spectral components of the focused continuum beam were spatially separated from each other. Thus, the nondegenerate TPA processes coming from different spectral components can be eliminated, and the direct nonlinear absorption spectrum attributed to degenerate TPA processes can be readily obtained. Using this new technique, the complete TPA spectra for these five highly two-photon-active compounds (AF-380, AF-350, AF-295, AF-270, and AF-50) were obtained in the spectral range from 600 to 950 nm on an absolute scale of TPA cross section. The relationship between the molecular structures and their TPA spectral behaviors are discussed. In general the measured TPA spectra are not identical with the linear absorption spectra on the scale of absorbed photon(s) energy. Moreover, for some sample (such as AF-380), the TPA spectrum is totally different from the linear spectrum, which implies the difference of molecular transition pathways and selection rules for one- and two-photon excitation processes. At high excitation intensity levels (>or=15 GW/cm(2)), the saturation behavior of TPA transition can be observed obviously in AF-350 and AF-380 solutions that exhibit much higher nonlinear absorptivity than the other chromophores investigated. 相似文献
55.
Jürgen Hartmann Ramamurthi Muthukrishnan Manfred Schlosser 《Helvetica chimica acta》1974,57(7):2261-2275
1,4-Dienes, vinyl ethers, allyl ethers, allyl thioethers and propene-thiolates are efficiently metalated by butyllithium in the presence of an activator such as potassium t-butoxide. Since the solvent, the counter-ion or the temperature may be varied before subsequent treatment with an electrophilic reagent, the critical ratio of direct vs. vinylogous attack (substitution at the α- or γ-position, respectively) can usually be adjusted within large limits. In many cases stereo-selectivity is achieved as well. 相似文献
56.
We study soliton solutions in supersymmetric scalar field theory with a class of potentials. We study both bosonic and fermionic zero-modes around the soliton solution. We study two possible couplings of gauge fields to these models. While the Born–Infeld like coupling has one normalizable mode (the zero mode), the other kind of coupling has no normalizable modes. We show that quantum mechanical problem which determines the spectrum of fluctuation modes of the scalar, fermion and the gauge field is identical. We also show that only the lowest lying mode, i.e., the zero mode, is normalizable and the rest of the spectrum is continuous. 相似文献
57.
Salim Saranya Sankaran Radhika Cheriya Mukkolakkal Afsina Abdulla Gopinathan Anilkumar 《Journal of heterocyclic chemistry》2021,58(8):1570-1580
The synthesis of heterocyclic compounds has been a hot topic for several decades. Synthetic organic chemists are always in search of new methodologies which are greener for the synthesis of heterocyclic compounds. The ultrasound-assisted reactions have contributed much to this field. This review focuses on the impact of sonochemistry in the synthesis of heterocyclic compounds and covers the literature from 2009 to 2020. 相似文献
58.
Shrikar M. BhosaleAadil A. Momin Rupesh L. GawadeVedavati G. Puranik Radhika S. Kusurkar 《Tetrahedron letters》2012,53(39):5327-5330
An efficient method has been established for the preparation of 1,2-diketones by unexpected C-C bond cleavage in 4-keto-2-hydroxy esters using pyridiniumchlorochromate (PCC). 相似文献
59.
K. SangeethaR. Ramesh Babu P. KumarG. Bhagvannarayana K. Ramamurthi 《Applied Surface Science》2011,257(17):7573-7578
l-arginine monohydrochloride monohydrate (LAHCl) single crystals have been implanted with 100 keV H+ ions at different ion fluence ranging from 1012 to 1015 ions/cm2. Implanted LAHCl single crystals have been investigated for property changes. Crystal surface and crystalline perfection of the pristine and implanted crystals were analyzed by atomic force microscope and high-resolution X-ray diffraction studies, respectively. Optical absorption bands induced by colour centers, refractive index and birefringence, mechanical stability and dielectric constant of implanted crystals were studied at different ion fluence and compared with that of pristine LAHCl single crystal. 相似文献
60.
One of the novel benzylidene aniline derivatives, 4-bromo-4′-hydroxybenzylidene aniline (BHBA) was synthesized and single crystal of BHBA was grown from solution following slow evaporation method at room temperature. Unit cell parameters of the grown crystal were determined from single crystal X-ray diffraction studies. Functional groups of BHBA were identified from Fourier transform infrared spectral study. UV–vis-NIR analysis of BHBA showed that the crystal is transparent between wavelengths 400 and 1100 nm. Thermal stability of the title compound was examined by thermogravimetric and differential scanning calorimetric studies. Fluorescence spectrum of the grown crystal recorded using spectrofluorometer shows emission peak at 450 nm. The second harmonic generation efficiency of BHBA estimated by Nd:YAG pulsed laser employing the Kurtz powder technique is ∼1.3 times that of potassium dihydrogen orthophosphate. Microhardness studies reveal that BHBA possesses high Vickers hardness value. The dielectric measurements were carried out at different temperatures and frequencies and the results are discussed. 相似文献