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31.
Tai-Ichi Shibuya Yasumasa J. I'haya Vincent McKoy 《International journal of quantum chemistry》1975,9(3):505-516
Dynamical screening in π-electron systems is studied by the equations of motion method. By using a partitioning technique on the equations of motion we can obtain simple expressions for the effect of dynamical screening directly on the transition energies and transition moments in π-electron systems. These results are used to study the effect of such screening in the N → V transition in ethylene. This procedure can be used to extend the equations-of-motion method to larger π-electron systems. 相似文献
32.
L-Daunosamine, the carbohydrate component of a group of important anticancer anthracycline antibiotics, has been efficiently prepared from L-lactic acid in a completely stereoselective manner through direct C-acylation using diphenyl phosphorazidate (DPPA). 相似文献
33.
The cyclic peptide proposed for the structure of the powerful cell growth inhibitory dolastatin 3, its diastereomers, and their isomers on the reverse order have been synthesized by the use of diphenyl phosphorazidate(DPPA) and diethyl phosphorocyanidate(DEPC). Their physicochemical and biological properties have shown that the proposed structure is untenable. 相似文献
34.
35.
Aoto T Ito K Hikosaka Y Shibasaki A Hirayama R Yamamono N Miyoshi E 《The Journal of chemical physics》2006,124(23):234306
The N2(+) states lying in the ionization region of 26-45 eV and the dissociation dynamics are investigated by high-resolution threshold photoelectron spectroscopy and threshold photoelectron-photoion coincidence spectroscopy. The threshold photoelectron spectrum exhibits several broad bands as well as sharp peaks. The band features are assigned to the N2(+) states associated with the removal of an inner-valence electron, by a comparison with a configuration interaction calculation. In contrast, most of the sharp peaks on the threshold photoelectron spectrum are allocated to ionic Rydberg states converging to N2(2+). Dissociation products formed from the inner-valence N2(+) states are determined by threshold photoelectron-photoion coincidence spectroscopy. The dissociation dynamics of the inner-valence ionic states is discussed with reference to the potential energy curves calculated. 相似文献
36.
37.
Horinouchi Y Tsuchiya K Taoka C Tajima S Kihira Y Matsuda Y Shishido K Yoshida M Hamano S Kawazoe K Ikeda Y Ishizawa K Tomita S Tamaki T 《Chemical & pharmaceutical bulletin》2011,59(2):208-214
Recently, increasing evidence suggests that the antihypertensive drug nifedipine acts as a protective agent for endothelial cells, and that the activity is unrelated to its calcium channel blocking. Nifedipine is unstable under light and reportedly decomposes to a stable nitrosonifedipine (NO-NIF). NO-NIF has no antihypertensive effect, and it has been recognized as a contaminant of nifedipine. The present study for the first time demonstrated that NO-NIF changed to a NO-NIF radical in a time-dependent manner when it interacted with human umbilical vein endothelial cells (HUVECs). The electron paramagnetic resonance (EPR) signal of NO-NIF radicals in HUVECs showed an asymmetric pattern suggesting that the radicals were located in the membrane. The NO-NIF radicals had radical scavenging activity for 1,1-diphenyl-2-picrylhydrazyl, whereas neither NO-NIF nor nifedipine did. In addition, the NO-NIF radical more effectively quenched lipid peroxides than NO-NIF or nifedipine. Furthermore, NO-NIF attenuated the superoxide-derived free radicals in HUVECs stimulated with LY83583, and suppressed iron-nitrilotriacetic acid (Fe-NTA)-induced cytotoxicity in rat pheochromocytoma (PC12) cells. Our findings suggest that NO-NIF is a candidate for a new class of antioxidative drugs that protect cells against oxidative stress. 相似文献
38.
Yasumasa Matsumoto 《Tetrahedron letters》2010,51(2):404-12975
Chiral C2-symmetric N-heterocyclic carbenes (NHCs) were tested for their stereocontrolling abilities in gold(I)-catalyzed asymmetric cyclization of 1,6-enynes giving the corresponding cyclopentane derivatives with moderate enantioselectivity of up to 59%. 相似文献
39.
The enantiomers of (11Z,19Z)-3-acetoxy-11,19-octacosadien-1-ol were synthesized from the enantiomers of 3,4-epoxy-1-butanol PMB ether. Its racemate was also synthesized. Its (S)-isomer and racemate were shown to possess the same pheromone activity as CH503, a long-lived inhibitor of male courtship in Drosophila melanogaster, although the racemate was less active. 相似文献
40.
The combination of xylenol orange (XO) and poly(diallyldimethylammonium chloride) (PDADMAC) has been utilized as a colorimetric sensor for selective recognition of Ni2+ in aqueous solution. Upon addition of Ni2+, the chemosensor exhibited the significant color change from red to purple with a bathochromic shift, whereas these change was not induced by other metal ions. XO alone did not recognize Ni2+ colorimetrically, indicating that PDADMAC was required for detecting Ni2+. This study can provide the facile method for the construction of new chemosensors by a simple mixture of an anionic water-soluble dye and cationic polyelectrolyte. 相似文献