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141.
Yasuhiro Kawanami Yoshio Ito Toshiyuki Kitagawa Yoshiyuki Taniguchi Tsutomu Katsuki Masaru Yamaguchi 《Tetrahedron letters》1984,25(8):857-860
trans-2,5-Bis(methoxymethyl)- and trans-2,5-bis(methoxymethoxymethyl)pyrrolidines proved to be excellent chiral auxiliaries for the asymmetric alkylation of the corresponding carboxyamide enolates giving good chemical yield and high stereoselectivity (invariably over 95% de), with remarkable flexibility to substrates and reaction conditions. 相似文献
142.
Ohta K Koketsu E Nagase Y Takahashi N Watanabe H Yoshimatsu M 《Chemical & pharmaceutical bulletin》2011,59(9):1133-1140
Direct scandium- and lanthanum-catalyzed etherifications of propargyl alcohols 1 and 6 in MeNO?-H?O provided propargyl ethers 3, 4 and 7 in high yields. In addition, reactions of 1 and 6 with thiols exclusively yielded the corresponding propargyl sulfides. 相似文献
143.
Gruner KK Hopfmann T Matsumoto K Jäger A Katsuki T Knölker HJ 《Organic & biomolecular chemistry》2011,9(7):2057-2061
Iron-mediated oxidative cyclisation provides an efficient approach to pyrano[3,2-a]carbazole alkaloids. Thus, improved routes to girinimbine and murrayacine as well as the first total syntheses of O-methylmurrayamine A and 7-methoxymurrayacine are reported. Asymmetric epoxidation of girinimbine led to (-)-trans-dihydroxygirinimbine and the assignment of its absolute configuration. 相似文献
144.
K Ino Y Kanno T Nishijo T Goto T Arai Y Takahashi H Shiku T Matsue 《Chemical communications (Cambridge, England)》2012,48(68):8505-8507
This report describes the electrochemical detection of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device consisting of 256 sensors. The time-course analyses showed that the redox compound in the droplet was dynamically changed during droplet evaporation or mass transfer through a water/oil interface. 相似文献
145.
Electronic structures of chemisorption on Si(111)/H,C1 are investigated by the first principle DV-Xα cluster method. The calculations are carried out for chemisorption on different sites, based on the Si13H15 cluster, and the effect of surface vacancy and buckling on the electronic structure is examined in detail. The present calculation shows that the Si13H15 surface cluster reproduces very well the more sophisticated band calculation for the Si(111) surface. It is concluded that the vacancy model with chemisorbed atoms at appropriate sites is reasonable to interpret the observed UPS of Si(111) 7 × 7/H,C1. The charge transfer between the substrate atom and the adatom depends strongly both on the chemisorption sites and on the electronegativitv difference. 相似文献
146.
Antifluorite type solid electrolytes, Li2+x-y-z[(NH)1-x-y-zNxClyHz] have been synthesized from Li3N, LiCl and LiCl·H2O or ]. Either of the last two compounds introduces NH2- ions into the product and is indispensable to form the antifluorite type structure. The lattice parameter decreases with increasing amount of NH2- ions in the compound, reflecting the difference of anion sizes between Cl- and NH2- ions. Activation energies of Li+ diffusive motion, derived from both conductivity and NMR measurements, increase with concentration of NH2- ions, although the values differ by a factor of ≈2 netween the both methods. 相似文献
147.
148.
Ikuma Kuroda Toshiharu Nagai Hoyo Mizobe Nobuhito Yoshimura Naohiro Gotoh Shun Wada 《Analytical sciences》2008,24(7):865-869
A polymeric ODS column was applied to the resolution of triacylglycerol positional isomers (TAG-PI), i.e. 1,3-dioleoyl-2-palmitoyl-glycerol (OPO) and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), with a recycle HPLC system. To investigate the ODS column species and the column temperatures for the resolution of a TAG-PI pair, a mixture of OPO and OOP was subjected to an HPLC system equipped with a non-endcapped polymeric, endcapped monomeric, endcapped intermediate, or non-endcapped monomeric ODS column at three different column temperatures (40, 25, or 10 degrees C). Only the non-endcapped polymeric ODS column achieved the separation of OPO and OOP, and the lowest column temperature (10 degrees C) showed the best resolution for them. The other pair of TAG-PI, a mixture of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO) was also subjected to the system equipped with a non-endcapped polymeric or monomeric ODS column at five different column temperatures (40, 32, 25, 17, and 10 degrees C). Thus, POP and PPO were also separated on only the non-endcapped polymeric ODS column at 25 degrees C. However, no clear peak appeared at 10 degrees C. These results would indicate that the polymeric ODS stationary phase has an ability to recognize the structural differences between TAG-PI pairs. Also, the column temperature is a very important factor for separating the TAG-PI pair, and the optimal temperature would relate to the solubility of TAG-PI in the mobile phase. Furthermore, the recycle HPLC system provided measurements for the separation and analysis of TAG-PI pairs. 相似文献
149.
150.