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991.
Three new purine derivatives, namely, 4-caryboxy-5,6-dihydro-4H,8H-pyrimido[1,2,3-cd]purine-8,10(9H)-dione (1), 7,9-dihydro-1-(3-oxobutyl)-1H-purine-6,8-dione (2), and 7-hydro-9-(3-oxobutyl)-1H-purine-6,8-dione (3) together with six known purine and pyrimidine derivatives were isolated from the EtOH/CH(2)Cl(2) extracts of the South China Sea gorgonian Subergorgia suberosa. The structures of 1-3 were determined on the bases of extensive spectroscopic analysis, including 1D and 2D NMR data. 相似文献
992.
Jing‐Yi JIN Shou‐Feng WANG Wei XUAN Ji‐Wen SHENG Si‐Hong WANG Guan‐Rong TIAN 《中国化学》2008,26(1):153-157
Both enantiomers of 2‐benzyl‐5‐bromo‐4‐oxopentanoic acid were prepared utilizing the diazo ketones as the key intermediates. The compounds were assayed for inhibitory activity against carboxypeptidase A (CPA, EC 3.4.17.1). The (R)‐form is 260‐fold more potent than the corresponding (S)‐form. The finding that (R)‐form, which belongs to the L‐series, is mostly responsible for the inhibitory activity accords with the substrate specificity of CPA. For comparison, both the optical forms of 2‐benzyl‐4‐oxopentanoic acid were also synthesized and evaluated as the inhibitors against CPA. These results reveal that the introduction of a bromo group at the α‐position of ketones can significantly enhance the electrophilicity of the carbonyl group. Further molecular docking study suggested that the gem‐diol form of the α‐bromo ketone, which mimics the transition state in the CPA catalytic process, could chelate the zinc ion in the active site of CPA and thus result in the strong inhibition. 相似文献
993.
994.
Xiang Wen Kong a Yi Hua Zhang a Li Dai b Hui Ji b Yi Sheng Lai a Si Xun Peng a a Center of Drug Discovery China Pharmaceutical University Nanjing China b Department of Pharmacology China Pharmaceutical University Nanjing China 《中国化学快报》2008,19(2):149-152
A series of novel nitric oxide-donating sixalkoxyl biphenyl derivatives (14a-1) were synthesized by coupling furoxan with alkoxyl biphenyl skeleton using amino acids as the spacers, and their cytotoxicity against HepG2 cells in vitro were evaluated by MTT method. It was found that 14c, 14d, 14f, 14i, 14j and 14k showed more potent cytotoxic activities than control 5-fluorouracil. NO release assay of target compounds indicated that the maximum amount of NO released by most active compounds 14c and 14j was about 6 × 10^-2 μmol/L, whereas 14a and 14h with very weak activity only released NO of 1 × 10^-2 μmol/L. 相似文献
995.
Si Guo Yuan Shao Hui Zhang Wei Hua Zou Yong Hao Zhou Xiao Hui Zhou 《中国化学快报》2008,19(5):611-614
A kind of pseudo-hypercrosslinked polymer resin was firstly synthesized via a continuous Friedel-Crafts alkylation poly- merization of benzene, diphenyl and their dichloromethyl derivatives. And the micromorphology and adsorption properties of these resins were investigated. The results demonstrated that the novel resins have high-specific surface area (581.26-974.88 m^2/g), high- pore volume (0.56-1.65 mL/g), small average porous radius (1.93-3.67 nm) and excellent adsorption properties for small non-polar organic molecules. 相似文献
996.
α-{3-[2-hydroxy-3-(N-methyl-N-hydroxyethylamino)propoxy]propyl}-ω-butylpolydimethylsiloxanes Ⅲ with various moleculax weights were prepared by epoxy addition of α-[3-(2,3-epoxy-propoxy)propyl]-ω-butylpolydimethylsiloxanes Ⅱ and Nmethylmonoethanolamine.At each step.the outcome compounds were characterized through FT-IR and NMR spectra,the results showed that each step was successfully carried out and objective products were achieved. 相似文献
997.
Tun Hai Xu Gang Lv Tong Hua Liu Ya Juan Xu Yun Shan Si Sheng Xu Xie Hong Feng Zhao Dong Han Dong Ming Xu 《中国化学快报》2008,19(7):817-820
A new tdterpenoid glycoside, 3-β-O-β-D-glucopyranosyl presenegenin 28-O-α-L-arabipyranosyl(1 → 3)-6-β- xylopyranosyl(1 → 4)-[β-D-apiofuranosyl(1 → 3)]-Ct-L-rhamnopyranosyl(1 → 2)-[α-L-rhamnopyranosyl(1 → 3)]-β-D-fucopyranosyl ester (1) was isolated from the Polygala tenuifolia Willd., together with two known saponins, including polygalasaponinXXIV (2) and polygalasaponinXXVIII (3). The structure of new compound was elucidated by spectroscopic methods. 相似文献
998.
Phan Quoc Khanh Lai Jiu Lin Vo Si Trong Long 《Mathematical Methods of Operations Research》2014,79(3):253-272
In this paper, we establish a continuous selection theorem and use it to derive five equivalent results on the existence of fixed points, sectional points, maximal elements, intersection points and solutions of variational relations, all in topological settings without linear structures. Then, we study the solution existence of a number of optimization-related problems as examples of applications of these results: quasivariational inclusions, Stampacchia-type vector equilibrium problems, Nash equilibria, traffic networks, saddle points, constrained minimization, and abstract economies. 相似文献
999.
Lingtao Fang Jian Hu Chuan Wei Zhang Jialun Wei Hai Chao Yu Si Yu Zheng Zi Liang Wu Qiang Zheng 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2280-2288
Forming carboxyl-Fe3+ coordination bonds as physical crosslinks is an effective strategy to develop tough hydrogels. Considering the inhibition of ferric ions on free-radical polymerization, these coordination bonds cannot be formed during the reaction, and a soaking process of preformed hydrogels is usually required for mechanical enhancement, resulting in uncontrollable gradient structure, long preparation time, and unnecessary waste of metallic ions. A facile strategy is reported here to prepare tough metallosupramolecular hydrogels by polymerization and in situ formation of coordination bonds with phosphates as the temporal ligands of Fe3+ ions. The phosphate ligands in the precursor solution form coordination complexes with the Fe3+ ions, which avoids the inhibition and ensures the polymerization. After swelling the resultant hydrogel in water, the ligands are substituted by carboxyl groups of the gel matrix due to the variation of local pH. The equilibrated hydrogel with carboxyl-Fe3+ coordination bonds as the physical crosslinks possesses excellent mechanical properties that can be tuned over a wide range by adjusting the polymer compositions and the concentrations of phosphate ligands and Fe3+ ions. This strategy should be applicable to other systems to enable synthesis of functional hydrogels with Fe3+ ions as the additive toward specific applications in engineering and biomedical fields. 相似文献
1000.
Huang Zhong Li Botong Si Xinhui Yao Chanjuan 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1287-1298
Journal of Thermal Analysis and Calorimetry - In order to avoid insufficient sterilization caused by uneven heating and nutrition loss generated by excessive heating, researchers and scientists... 相似文献