排序方式: 共有27条查询结果,搜索用时 15 毫秒
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Antony J. Davies Karel M.J. Brands Cameron J. Cowden Ulf-H. Dolling David R. Lieberman 《Tetrahedron letters》2004,45(8):1721-1724
The ortho-alkylation of Boc-protected aminopyridines with α,ω-dihaloalkanes followed by in situ cyclisation, resulted in the corresponding annulated pyridine derivatives in good to excellent yields. The effect of the alkylating and chelating agents, the transmetallation additives and the directing group was examined. 相似文献
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Engelhardt FC Shi YJ Cowden CJ Conlon DA Pipik B Zhou G McNamara JM Dolling UH 《The Journal of organic chemistry》2006,71(2):480-491
[reaction: see text] A newly developed synthesis of a NO-releasing prodrug of rofecoxib is described. The highly productive process consists of five chemical steps and produces prodrug 1 in an overall 64% yield from commercially available 3-phenyl-2-propyn-1-ol (4). The synthesis is highlighted by the carbometalation reaction of propargyl alcohol 4 to generate the tetrasubstituted olefin core, sulfone acid 2. Additionally, two alternate end-game strategies to prepare NO-COXIB 1 from this intermediate were explored and developed: (1) a convergent synthesis where a bromonitrate side chain is introduced in one step and (2) a two-step sequence that first installs the requisite six-carbon ester side chain followed by chemoselective nitration. 相似文献
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Janet Cowden Vassilev 《Transactions of the American Mathematical Society》1998,350(10):4041-4051
Let be an -finite regular local ring and an ideal contained in . Let . Fedder proved that is -pure if and only if . We have noted a new proof for his criterion, along with showing that , where is the pullback of the test ideal for . Combining the the -purity criterion and the above result we see that if is -pure then is also -pure. In fact, we can form a filtration of , that stabilizes such that each is -pure and its test ideal is . To find examples of these filtrations we have made explicit calculations of test ideals in the following setting: Let , where is either a polynomial or a power series ring and is generated by monomials and the are regular. Set . Then .
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The technique of ferromagnetic resonance at 23 GHz has been used to determine the first three anisotropy constants of pure Ni down to 4.2K. A temperature and orientation dependent linewidth has also been observed. 相似文献
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Bio MM Xu F Waters M Williams JM Savary KA Cowden CJ Yang C Buck E Song ZJ Tschaen DM Volante RP Reamer RA Grabowski EJ 《The Journal of organic chemistry》2004,69(19):6257-6266
A practical, efficient synthesis of 1, a hepatitis C virus RNA replication inhibitor, is described. Starting with the inexpensive diacetone glucose, the 12-step synthesis features a novel stereoselective rearrangement to prepare the key crystalline furanose diol intermediate. This is followed by a highly selective glycosidation to couple the C-2 branched furanose epoxide with deazapurine. 相似文献