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881.
[reaction: see text] The phosphoramidite 11 was prepared in three steps from methyl 2-mercaptoacetate and demonstrated efficiency in the synthesis of conventional 5'-/3'-phosphate/thiophosphate monoester derivatives of 2'-deoxyribonucleosides and DNA oligonucleotides. Moreover, the use of 11 has enabled the preparation of the dinucleoside phosphorothioate analogue 26 in high yields (>95%) with minimal cleavage (<2%) of the thermolytic thiophosphate protecting group. 相似文献
882.
Marta Grzanek Anna Michalak Andrzej Rogowski 《Nonlinear Analysis: Theory, Methods & Applications》2008
The problem of Lyapunov stability for systems of ODE’s of Caratheodory type is considered. It is proved that without the necessity of calculating Dini or Clarke generalized gradients, the locally Lipschitz Lyapunov function can follow different kinds of stability. 相似文献
883.
Yao Yun Hu Jing Mei Yin Da Bin Gao Ying Ping Jia Guang Yun Zhou Ying Na Cui Shen Min Li 《中国化学快报》2008,19(5):529-532
Photopromoted carbonylation of 1-bromo-6-chlorohexane with CO catalyzed by CuBr2 and CdI2 has been carried out under ambient conditions. The results indicate that the carbonylation proceeds with the major product of chloroester ClCH2(CH2)5COOCH3 under catalysis of CuBr2. Furthermore, the activity of the carbonylation can be improved by addition of basic additives (NaOAc, Na3PO4 or (n-C4H9)3N). Among these additives, (n-C4H9)3N is the most efficient in terms of the yield of ClCH2(CH2)5COOCH3. However, the methoxycarbonyl substituting chlorine product of BrCH2(CH2)5COOCH3 is not obtained in the presence of CdI2. This is quite different from the carbonylation of monochloroalkane. 相似文献
884.
Andrzej Grzechnik 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(10):i63-i65
The crystal structure of tetrabismuth tris(germanate), Bi4Ge3O12 (I3d, Z = 4), is stable to at least 7.30 GPa, as demonstrated by hydrostatic single‐crystal X‐ray diffraction measurements in a diamond anvil cell at room temperature. The highest pressure reached in this study is close to the onset of amorphization at about 8 GPa. The Bi and Ge atoms are located at the 16c (3) and 12a () Wyckoff positions, respectively. The compression mainly affects the distorted BiO6 octahedra, while the GeO4 tetrahedra are relatively rigid. When compared with the values obtained under ambient conditions, the long Bi—O distances decrease with increasing pressure, while the short Bi—O distances do not change. 相似文献
885.
K Kordatos T Da Ros S Bosi E Vázquez M Bergamin C Cusan F Pellarini V Tomberli B Baiti D Pantarotto V Georgakilas G Spalluto M Prato 《The Journal of organic chemistry》2001,66(14):4915-4920
We report the synthesis of three novel, versatile fullerene intermediates whose main feature is the presence of an amino end group. Simple condensation reactions of these intermediates under standard conditions produce new derivatives that are useful for applications in materials science and medicinal chemistry. 相似文献
886.
Jia Rong Li Li Jun Zhang Xi Quan Yang Qing Li Dong Wang Chun Xia Wang Da Xin Shi Qi Zhang 《中国化学快报》2008,19(1)
Two different skeletons of heterocyclic compounds, quinoline and quinazolinone analogs could be obtained by a novel one-potsynthesis from substituted 3-amino-lH-benzo[f]chromene-2-carbonitrile derivatives and cyclohexanone in DMF in the catalyst ofanhydrous zinc chloride under reflux. A plausible mechanism was proposed. 相似文献
887.
888.
Jan Kratochvíl Andrzej Proskurowski Oriol Serra 《Discrete Applied Mathematics》2009,157(12):2575-2576
889.
890.
A k-uniform hypergraph is hamiltonian if for some cyclic ordering of its vertex set, every k consecutive vertices form an edge. In 1952 Dirac proved that if the minimum degree in an n-vertex graph is at least n/2 then the graph is hamiltonian.
We prove an approximate version of an analogous result for uniform hypergraphs: For every K ≥ 3 and γ > 0, and for all n large enough, a sufficient condition for an n-vertex k-uniform hypergraph to be hamiltonian is that each (k
− 1)-element set of vertices is contained in at least (1/2 + γ)n edges.
Research supported by NSF grant DMS-0300529.
Research supported by KBN grant 2P03A 015 23 and N201036 32/2546. Part of research performed at Emory University, Atlanta.
Research supported by NSF grant DMS-0100784. 相似文献