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991.
A formal synthesis of semiaquilegin A is achieved starting from readily available oridonin in 19 linear steps. The absolute configuration of the natural product has been established. A variety of useful analogues were prepared through this synthetic route. 相似文献
992.
Jia‐Jian Wang Hua‐Ming Zeng Zhi‐Gang She Cheng‐Du Miao Kui Hong Yu‐Cheng Gu Lan Liu Yong‐Cheng Lin 《Helvetica chimica acta》2011,94(10):1875-1880
Two new meroterpenes, ‘acetoxydehydroaustin B’ ( 1 ) and ‘1,2‐dihydro‐acetoxydehydroaustin B’ ( 2 ) were isolated in the form of a mixed crystal from the mangrove endophytic fungus Aspergillus sp. 085241B. Their structures and absolute configurations were determined by extensive analysis of their spectra and X‐ray diffraction data. In a preliminary bioassay, the mixed crystal did not exhibit activities against cancer cell lines of MDA‐MB‐435, SKBR3, HepG2, HEP3B, PC‐3, and A549, as well as against α‐glucosidase and tyrosinase. 相似文献
993.
Conjugatedpolymerswithlargethird-orderopticalnonlinearityhavebeedfocusedfortheirpromisingpotentialsforadvancedmaterialsapplications'.Recently,investigationsoftransitionmetalwithorganicligandsystemshavebeengreatlyintensifiedduetothedelectronsincorporatedintheconjugatedsystem,whichareexpectedtoellhancethehyperpolarizability.Phenylacetyleneandthemetalphenylacetylidesplayimportantrolesinformationofuniquecoordinatedc-lusters',butitseamsthatthestudyofmetalphenylacetylides,particularlyofthesilverphen… 相似文献
994.
Novel lanthanide coordination compounds with ciprofloxacin (CPFX), including eleven complexes Ln(CPFX)2Cl(H2O), (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb; n = 7, 8, 9) and crystalline [Ce(CPFX)2 (H2O)4] Cl (H2O)3.25 (C2H5‐OH)0.25, were synthesized. The crystal is of triclinic space group Pi with a= 1.3865(2) nm, b = 1.3899(3) nm, c = 1.6505(2) nm, a = 92.73(1)°, β= 114.39(1)°, γ=115.55 (1)°, Z = 2 and R = 0.0449. FT‐IR, electronic spectroscopy and X‐ray diffraction were employed to show that the lanthanide ion, which displays an eight‐coordinate structure, is chelated by 3‐carboxyl and 4‐keto oxygen donors of CPFX and two six‐membered chelate rings are formed. Test of in vitro antibacterial activity against E. coli, P. aeruginosa and S. aureus indicated that the in vitro antibacterial activity of the ligand can be improved by complexation with Ce(III). 相似文献
995.
The contribution of solvation energy to guiding molecular recognition for six rigid protein‐peptide systems bad been evaluated by the variation in the number of the identified native‐like configurations and in the driving force of specific interaction resulting from the addition of the explicit solvation term in the force field function. The AMBER force field energy and the total energy including the force field energy and the WZS solvation energy were calculated for sampled configurations. The results obtained by the calculations of both force field and total energies were compared with each other. It suggests that the contribution of solvation energy is important to guiding the specific recognition of the systems in which the ligands possess larger hydrophobic or aromatic residues while the protein receptors provide the active surfaces with hydrophobic property. 相似文献
996.
<正>LiCl-promoted superbase catalysts were found to be stable and highly selective to ethene for oxidative dehydrogenation of ethane,giving 84%ethane conversion and 74%ethene yield at 923 K.Results indicated that the stronger the basicity of LiC1-based catalysts,the better the catalytic performance. 相似文献
997.
Hai-lin Su ;Shao-long Tang ;Rui-long Wang ;Yi-qing Chen ;Chong Jia ;You-wei Du 《化学物理学报(中文版)》2009,(1):82-86
The effects of magnetic field annealing on the properties of Fe48Co52 alloy nanowire arrays with various interwire distances (Di=30-60 nm) and wire diameters (Dw=22-46 nm) were investigated in detail. It was found that the array's best annealing temperature and crys- talline structure did not show any apparent dependence on the treatment of applying a 3 kOe magnetic field along the wire during the annealing process. For arrays with small Dw or with large Di, the treatment of magnetic field annealing also had no obvious influence on their magnetic performances. However, such a magnetic field annealing constrained the shift of the easy magnetization direction and improved the coercivity and the squareness obviously for arrays with large Dw or with small Di. The difference in the intensity of the effective anisotropic field within the arrays was believed to be responsible for this different variation of the array's magnetic properties after magnetic field annealing. 相似文献
998.
Wei‐Ping Su Mao‐Chun Hong Rong Cao Jia‐Bao Weng Zhong‐Yuan Zhou S. C. Chan Albert 《中国化学》2001,19(9):817-821
The supramolecular silver(I)‐thiolate complex [Ag(μ2‐SC4N2H4)2(SCN)]n has been prepared from the reaction of AgSCN and pyrimidine‐2‐thiol in DMF. X‐ray diffraction analysis shows that the supramolecular structure exhibits one‐dimensional chain through the secondary Ag‐S interactions and the chains are further linked by strong hydrogen bonds to form a three dimensional network. The luminescence effect from the silver‐centered state of S→Ag LMCT in solid state is different from that in solution due to the secondary Ag‐S interactions. 相似文献
1000.
We performed the femtosecond two-color collinear optical Kerr shutter (OKS) measurements in a thick Kerr medium. The time-resolved OKS signals showed a multi-peak structure and a large broadening with respect to that for non-collinear. By measuring the time-resolved OKS signals in the sample at different powers, we demonstrated that the abnormal profile of the OKS signals was mainly attributed to self-focusing and re-focusing of the pump beam in the Kerr medium and the group velocity difference between the pump and the probe beams. 相似文献