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71.
[reaction: see text] N-Sulfinyl beta-amino Weinreb amides are prepared by condensation of sulfinimines with the potassium enolate of N-methoxy-N-methylacetamide. These new chiral building blocks are useful for the asymmetric synthesis of beta-amino carbonyl compounds, as illustrated here by the concise enantioselective syntheses of sedum alkaloids (+)-sedridine and (-)-allosedridine. 相似文献
72.
L. C. Tribedi K. G. Prasad P. N. Tandon 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,27(2):143-148
Single and double K-vacancy fractions at sulphur ions in Fe and Ni are measured for ion velocities between 7v 0 and 14v 0 (v 0=c/137) using the probe layer technique. The derived values for the degree of polarization of these ions from the available transient magnetic field data at a velocity of 8v 0 in Fe and Ni agrees with the general trends seen for light ions. 相似文献
73.
A general partial summation method for including arbitrary classes of diagrams to all orders in the coupled cluster based size consistent energy functional for closed shell states is developed. Since the various reduced density matrices which appear in the energy functional are essentially the time-independent analogues of the corresponding many body Green functions, it is possible to derive Dyson-like equations for these quantities. By expanding the associated proper self energy parts in terms of the T-amplitudes, one can carry out partial summations in the reduced density matrices and thus in energy. At a higher level, higher order terms in a proper self energy can also be generated by renormalizing the internal propagators in it, and considering only the irreducible self-energy terms. 相似文献
74.
Euchrenone a2 (7) isolated from the roots ofEuchresta japonica has been synthesised from 3-prenylphloroacetophenone (1) by other workers. We carried out its cyclodehydrogenation with dichloro dicyano quinone (DDQ) to obtain 6-acetyl-5,7-dihydroxy-2,2-dimethylchromene
(2) which was ethoxymethylated in the 7-position to give 6-acetyl-7-ethoxymethoxy-5-hydroxychromene (3). Chalcone condensation of3 and 4-ethoxymethoxy-3-C-prenylbenzaldehyde (4) gave 4,6′-bisethoxymethoxy-2′-hydroxy-6″, 6″-dimethyl-3-C-prenylpyrano (2″, 3″–4,3) chalcone (5) which cyclised with methanolic sodium acetate to give protected 5,4′-bisethoxymethoxy-6″, 6″-dimethyl-3′-C-prenylpyrano (2″, 3″–7,8) flavanone (6). Deprotection of6 with 4% methanolic HCl yielded (7) with melting point and spectral data identical to that of the natural compound. 相似文献
75.
The Brønsted acidity of the various Si(nAl) sites present in zeolites is evaluated from proton binding energy and LUMO energy calculated by the semiempirical MNDO quantum chemical method. The two calculated energy values both exhibit a linear correlation with the existing 29Si NMR chemical shift and the IR hydroxyl stretching frequency data. The inter-convertibility between different Si(nAl) sites during an alumination or dealumination process is also evaluated based on the calculated substitution energy. The results indicate that alumination processes are less favorable to occur in zeolites than dealumination processes and the latter is more likely to occur for Si(nAl) clusters that contain the maximum number of aluminum nearest neighbors. 相似文献
76.
Summary New potential tetradentate ligands, N-benzoyl-N-thiobenzohydrazide (H2BTBH) and N-salicyl-N-thiobenzohydrazide (H2SBTH) have been prepared and characterized. Their complexes with CoII, NiII and ZnII have been prepared and characterized on the basis of elemental analyses, magnetic susceptibility measurements, and u.v.-vis., i.r. and 1H-n.m.r. spectral studies. The bonding and stereochemistries of the complexes are discussed. H2BTBH, H2SBTH and the complexes have been screened towards a number of bacteria. 相似文献
77.
Dinesh Kumar Ashu Rani D. S. N. Prasad K. S. Gupta 《Reaction Kinetics and Catalysis Letters》1991,43(1):133-141
The kinetics of the oxidation of 2-furancarboxaldehyde by thallic perchlorate at 50°C obeys the rate law
相似文献
78.
Mahendra Madegowda Doreswamy Beeranahally H. Sridhar Mandayam A. Prasad Javaregowda S. Khanum Shaukath A. Shashikanth Sheena Sudha Belagur S. 《Structural chemistry》2004,15(3):211-214
Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P21/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity. 相似文献
79.
Ryzhov V Bundy JL Fenselau C Taranenko N Doroshenko V Prasad CR 《Rapid communications in mass spectrometry : RCM》2000,14(18):1701-1706
The performance of infrared (2.94 microm) and ultraviolet (337 nm) lasers were compared for analysis of purified spores of B. subtilis, B. cereus and B. globigii on a four-inch end-cap reflectron time-of-flight instrument. Infrared matrix-assisted laser desorption/ionization (IR-MALDI) mass spectra of these microorganisms displayed a larger number of biomarker peaks above m/z 4000, compared with UV-MALDI. Biomarker peaks were observed at higher m/z values with the IR laser. 相似文献
80.
We present a novel sensing scheme for detecting the effects of unburned fossil fuels by integrating microarray technology and dielectrophoresis to develop single-neuron arrays. These arrays have the capability to sense and identify the two fuels, at parts per billion (ppb) concentrations, as well to determine the associated physiological changes at the single-cell level. Identification is achieved through frequency domain analysis of the measured changes to the extracellular electrical activity due to the effect of the fossil fuels. This yields unique electrical identifiers known as "signature patterns". Simultaneous optical visualization to the physiological changes is obtained by specific fluorescent staining. The correlation between the signature patterns and the cellular biological behavior establishes the veracity of this identification technique. 相似文献
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