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111.
A convenient and efficient route to novel unsymmetrically disubstituted azetidin-2-ones is described. β-Lactam carbocation equivalents of type 1 and active aromatic substrates in the presence of a Lewis acid promote a facile and stereoselective C-3 substitution to provide monosubstituted β-lactams (3,4) and symmetrically disubstituted β-lactams (5). cis-3-(4′-Methoxyphenyl)-3-phenylthioazetidin-2-ones (4) undergo further substitution with active aromatic substrates mediated by a Lewis acid to afford unsymmetrically disubstituted azetidin-2-ones (7). 相似文献
112.
Freer M Casarejos E Achouri L Angulo C Ashwood NI Curtis N Demaret P Harlin C Laurent B Milin M Orr NA Price D Raabe R Soić N Ziman VA 《Physical review letters》2006,96(4):042501
The 10.15 MeV resonance in 10Be has been probed via resonant 6He+4He elastic scattering. It is demonstrated that it is the Jpi=4+ member of a rotational band built on the 6.18 MeV 0+ state. A Gammaalpha of 0.10-0.13 MeV and Gammaalpha/Gamma=0.35-0.46 were deduced. The corresponding reduced alpha width, gamma2alpha, indicates one of the largest alpha-cluster spectroscopic factors known. The deformation of the band, including the 7.54 MeV, 2+ member, is large (h2/2I=200 keV). Such a deformation and the significant degree of clusterization signals a well-developed alpha:2n:alpha molecular structure. 相似文献
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Treatment of various electron‐deficient alkenes in DMSO with stable, dry, equimolar mixtures of either Me3S(O)I/KOt‐Bu or Me3S(O)I/NaH cleanly afforded the corresponding substituted cyclopropanes in good yields and short reaction times (<20 min for reactions at 50–60°C using 0.4–4.0 mmol alkene). 相似文献
116.
Khan R Siddiq F Fatima I Yasmeen S Karim A Malik A Afza N Hameed S 《Natural product communications》2011,6(8):1083-1084
A new pregnane derivative, 2,6beta,7beta-trihydroxy-4-methyl-19-norpregna-1,3,5(10)-trien-17-one, has been isolated from the ethyl acetate soluble fraction of Potentilla evestita along with a pregnane derivative, 11alpha,17alpha,21-trihydroxypregna-4,16(22)-diene-3,20-dione, that is reported for the first time as a natural product. Their structures were elucidated with the aid of 1H and 13C NMR spectra and by COSY, HMQC, HMBC and NOESY experiments. 相似文献
117.
Loosely aggregated conjugated polymer nanoparticles (CPNs) were used as nontoxic and efficient small interfering RNA (siRNA) delivery vehicles with delivery visualization. A significant down regulation (94%) of a target gene was achieved by transfection of HeLa cells with the CPNs/siRNA complexes, supporting CPN as a promising siRNA delivery carrier. 相似文献
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Direct Evidence for a Peroxide Intermediate and a Reactive Enzyme–Substrate–Dioxygen Configuration in a Cofactor‐free Oxidase
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Dr. Soi Bui Dr. David von Stetten Dr. Pablo G. Jambrina Prof. Thierry Prangé Dr. Nathalie Colloc'h Dr. Daniele de Sanctis Dr. Antoine Royant Dr. Edina Rosta Dr. Roberto A. Steiner 《Angewandte Chemie (International ed. in English)》2014,53(50):13710-13714
Cofactor‐free oxidases and oxygenases promote and control the reactivity of O2 with limited chemical tools at their disposal. Their mechanism of action is not completely understood and structural information is not available for any of the reaction intermediates. Near‐atomic resolution crystallography supported by in crystallo Raman spectroscopy and QM/MM calculations showed unambiguously that the archetypical cofactor‐free uricase catalyzes uric acid degradation via a C5(S)‐(hydro)peroxide intermediate. Low X‐ray doses break specifically the intermediate C5? OO(H) bond at 100 K, thus releasing O2 in situ, which is trapped above the substrate radical. The dose‐dependent rate of bond rupture followed by combined crystallographic and Raman analysis indicates that ionizing radiation kick‐starts both peroxide decomposition and its regeneration. Peroxidation can be explained by a mechanism in which the substrate radical recombines with superoxide transiently produced in the active site. 相似文献
120.
Ştefan Ţălu Sebastian Stach Aman Mahajan Dinesh Pathak Tomas Wagner Anshul Kumar Ratish Kumar Bedi 《Surface and interface analysis : SIA》2014,46(6):393-398
This paper applies multifractal spectrum theory to characterize the structural complexity of 3D surface roughness of copper (II) tetrasulfophthalocyanine (CuTsPc) films on the indium tin oxide (ITO) substrate, obtained with atomic force microscopy (AFM) analysis. CuTsPc films were prepared by drop cast method on ITO substrate. CuTsPc films surface roughness was studied by AFM in tapping‐mode?, in air, on square areas of 2500 µm2. A novel approach, on the basis of computational algorithms for analysis of 3D roughness surface applied for AFM data, was presented. Results revealed that the 3D surface roughness of CuTsPc films prepared by drop cast method on ITO substrate can be described using the multifractal geometry. The generalized dimensions Dq and the multifractal spectrum f(α) provided quantitative values that characterize the local scale properties of CuTsPc films surface geometry at nanometer scale. Data provide valuable information to describe the spatial arrangement of 3D surface roughness of CuTsPc films on ITO substrate, which was not taken into account by classical surface statistical parameters. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献