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T Mimura H Nakajima K Tsujikawa M Haruyama B G Lee Y Kohama I Kohda M Iwai 《Chemical & pharmaceutical bulletin》1989,37(7):1946-1947
Bis[2-(E-2-alkenoylamino)ethyl] disulfides (compds. I), synthesized from cystamine and 2-trans fatty acids, inhibited collagen-induced rat and rabbit platelet aggregation. The most potent compound was bis[2-(E-2-hexenoylamino)ethyl] disulfide (compd. I-1), and this compound suppressed thromboxane B2 formation from arachidonic acid in rat platelets. The results suggested that compd. I-1 has an inhibitory effect on cyclooxygenase. 相似文献
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Miura K Hondo T Okajima S Nakagawa T Takahashi T Hosomi A 《The Journal of organic chemistry》2002,67(17):6082-6090
Acid-catalyzed intramolecular addition of a hydroxy group to alpha-alkylated vinylsilanes has been studied. Treatment of (Z)-5-alkyl-5-silyl-4-penten-1-ols 1 (R = alkyl) with 5 mol % TiCl(4) in CHCl(3) gave trans-2-alkyl-3-silyltetrahydropyrans 2 exclusively (trans/cis = >99/1 to 97/3). The cyclization efficiency and rate strongly depended on the geometry of the C-C double bond and the silyl group. The use of (E)-vinylsilanes resulted in lower yields with poor cis-selectivity. In the cyclization of (Z)-1 (R = Bu), the silyl group used, the reaction time, and the yield of 2 were as follows: SiMe(2)Ph, 9.5 h, 75%; SiMe(3), 7.5 h, 66%; SiMePh(2), 24 h, 58%; SiMe(2)-t-Bu, 0.75 h, 85%; SiMe(2)Bn, 1.5 h, 78%. This 1,2-silyl-migrative cyclization could be applied to stereoselective synthesis of trisubstituted tetrahydropyrans. The acid-catalyzed reaction of 1-, 2-, or 3-substituted (Z)-5-silyl-4-nonen-1-ols 8 gave r-2,t-3,c-6-, r-2,t-3,t-5-, or r-2,t-3,c-4-trisubstituted tetrahydropyrans with high diastereoselectivity, respectively. (Z)-4-Alkyl-4-silyl-3-buten-1-ols 5 as well as 1 underwent the 1,2-silyl-migrative cyclization to give 2-alkyl-3-silyltetrahydrofurans 6 with high trans-selectivity. This silicon-directed cyclization was also available for the stereoselective synthesis of tri- and tetrasubstituted tetrahydrofurans. 相似文献
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Kiyoshi Endo Hajime Tsujikawa Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1986,24(7):1633-1642
5-Phenyl-2-pentene (5Ph2P) was found to undergo monomer-isomerization polymerization with TiCl3–R3Al (R = C2H5 or i-C4H9, Al/Ti > 2) catalysts to give a polymer consisting of exclusively 5-phenyl-1-pentene (5Ph1P) unit. The geometric and positional isomerizations of 5Ph2P to its terminal and other internal isomers were observed to occur during polymerization. The catalyst activity of alkylaluminum examined to TiCl3 was in the following order: (C2H5)3Al > (i-C4H9)3Al > (C2H5)2AlCl. The rate of monomer-isomerization polymerization of 5Ph2P with TiCl3–(C2H5)3Al catalyst was influenced by both the Al/Ti molar ratio and the addition of nickel acetylacetonate [Ni(acac)2], and the maximum rate was observed at Al/Ti = 2.0 and Ni/Ti = 0.4 in molar ratios. 相似文献
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In the inflationary scenario of loop quantum cosmology in the presence of inverse-volume corrections, we give analytic formulas for the power spectra of scalar and tensor perturbations convenient to compare with observations. Since inverse-volume corrections can provide strong contributions to the running spectral indices, inclusion of terms higher than the second-order runnings in the power spectra is crucially important. Using the recent data of cosmic microwave background and other cosmological experiments, we place bounds on the quantum corrections. 相似文献
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We calculate the Borel–Moore homology of affine Springer fibers of type A associated with some regular semisimple nil elliptic elements. As a result, we obtain bigraded Sn-modules whose bigraded Frobenius series are a generalization of the symmetric functions introduced by Haglund, Haiman, Loehr, Remmel, and Ulyanov. 相似文献
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Recent developments of FT-IR and computer techniques made it possible to detect minute changes (temperature dependences etc.) in the infrared spectra of proteins in aqueous solution.In this paper we studied temperature dependences of the amide I and I bands of ribonuclease A (RNase A), calmodulin (CaM), and Ca2+-bound CaM in H2O and D2O solutions between 28°C and 70°C using the difference-spectrum and Fourier self-deconvolution techniques. 相似文献