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82.
Shin-ichi Furuhata Motonori Okajima Masato Abe Tetsuhisa Goto Hidefumi Makabe 《Tetrahedron》2008,64(33):7695-7703
Total synthesis of pyranicin and its deoxygenated analogues was achieved using Cl2Pd(CH3CN)2 catalyzed diastereoselective cyclization of the allylic ester as the key step. The inhibitory activity of these compounds for mitochondrial NADH-ubiquinone oxidoreductase (complex I) was poorer than those of ordinary mono-THF acetogenins such as annonacin. 相似文献
83.
Yasukochi H Atago T Tanaka A Nakatsuji H Yoshida E Kakehi A Nishii Y Tanabe Y 《Organic & biomolecular chemistry》2008,6(3):540-547
We performed an efficient practical and systematic optical resolution method for gem-dihalo- and monohalocyclopropanecarboxylic acids and utilizing chiral 1,1'-binaphthol monomethyl ether (R)- as the key auxiliary. Direct esterification of with (R)- gave two 1R- and 1S-diastereomeric esters with marked different R(f) values, both of which were easily separated using simple column chromatography. Monodehalogenation of separated chiral esters using t-BuMgCl and cat. Co(dppe)(2)Cl(2) gave two 1,2-trans- and 1,2-cis-diastereomers with markedly different R(f) values, both of which were similarly separated using simple column chromatography. The obtained diastereomers and were easily hydrolyzed to the desired enantiopure acids (>99%) and (>99%), respectively, with recovery of (R)-, both in good to excellent yields. Utilizing the present method, important chiral agrochemicals, carpropamid and fencyclate , were readily synthesized. Pyrethroid with three asymmetric centers was efficiently synthesized in a much better yield compared with the reported method. 相似文献
84.
Tin-free Giese reaction and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. The reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine and carbon-chlorine bonds. The iodine atom transfer followed by hydride reduction of the resulting carbon-iodine bond is proposed as a possible mechanism. 相似文献
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88.
Masahiro Yoshita Yuhei Hayamizu Hidefumi Akiyama Loren N. Pfeiffer Ken W. West 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):230
A T-shaped single quantum-wire laser with high spatial uniformity has been fabricated by a cleaved-edge overgrowth method with molecular beam epitaxy and a growth-interrupt annealing technique. Using micro-photoluminescence imaging and spectroscopy, we confirmed the formation of a spatially uniform quantum wire over 20 μm long without hetero-interface roughness. By optical pumping, we achieved single-mode lasing from the ground state of the single quantum wire at a threshold excitation power as low as 5 mW at 5 K. 相似文献
89.
The dynamic heat capacity of nematic liquid crystals just above the clearing point is calculated as an extension of our previous theory of static heat capacity. The present theory explains semi-quantitatively the available experimental results of anomalous ultrasonic absorption and dispersion. 相似文献
90.