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881.
Yamada Ki Harwood SJ Gröger H Shibasaki M 《Angewandte Chemie (International ed. in English)》1999,38(23):3504-3506
The best ratio is 1:1:3 for the components Yb, K, and binaphthol in the new heterobimetallic complex, which efficiently catalyzes an asymmetric nitro-Mannich-type reaction. The desired nitro-Mannich products 2 are obtained with up to 91 % ee starting from N-phosphinoyl imines 1. 相似文献
882.
Harada T Hiraoka Y Kusukawa T Marutani Y Matsui S Nakatsugawa M Kanda K 《Organic letters》2003,5(26):5059-5062
Bis-BINOLs 7a-c in which two BINOL units are tethered by phenylenebis(ethynyl) groups react with titanium tetraisopropoxide (2 equiv) to form intramolecular dimeric titanium(IV) aggregates 2a-c. Of these, 2a,b with an o-phenylenebis(ethynyl) tether are stable in the presence of excess titanium tetraisopropoxide. Complex 2a exhibits a relatively high enantioselectivity in asymmetric addition of diethylzinc to an aldehyde. [structure: see text] 相似文献
883.
Duong HM Bendikov M Steiger D Zhang Q Sonmez G Yamada J Wudl F 《Organic letters》2003,5(23):4433-4436
[reaction: see text] A twistacene, 6,8,15,17-tetraphenyl-1.18,4.5,9.10,13.14-tetrabenzoheptacene (3), was synthesized using a mild and novel bisbenzyne precursor. It was characterized by X-ray crystallography, NMR, UV-vis, and IR spectroscopies, as well as cyclic voltammetry and DFT calculations. The heptacene derivative possesses a nonpropeller twist topology and is unusually stable for a highly conjugated oligoacene. In addition, it is fluorescent, with a quantum efficiency of 15%. Distortion from planarity, mostly due to the phenyl substituents, causes only marginal changes in electronic properties and is beneficial for redox reversibility, which is required for efficient OLED devices. 相似文献
884.
Hatsuo Yamamura Yuichi Yamada Rie Miyagi Kazuaki Kano Shuki Araki Masao Kawai 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(3-4):211-216
Three isomers of -cyclodextrin derivatives 2a–c possessing two trimethylammonio groups on their C(6) atoms were prepared by reaction of the corresponding regioisomers of diamino compounds with methyl iodide. These derivatives recognize chiral guests through three-point interactions composed of both Coulomb interactions by the two cationic moieties and hydrophobic interaction by the molecularcavity. 相似文献
885.
Yamada S Wang D Li S Nishikawa M Qian EW Ishihara A Kabe T 《Chemical communications (Cambridge, England)》2003,(7):842-843
A sulfur exchange reaction between di-tert-butylpolysulfides and elemental sulfur was examined using a 35S tracer method and the reaction mechanism was discussed. 相似文献
886.
Kiso Y Kuzawa K Saito Y Yamada T Nagai M Jung YJ Min KS 《Analytical and bioanalytical chemistry》2002,374(7-8):1212-1217
Phosphate is generally analyzed by color intensity of phosphoantimonylmolybdenum blue (PAMB): especially by a spot test based on spectrophotometric or visual determination. Visual determination is one of the simplest and most inexpensive methods; however, it is believed to be of low precision. In this work, we have developed an alternative phosphate spot test, where phosphate concentration is measured by the color band length of PAMB formed in a detection tube similar to a gas detection tube. The color band is formed by the entrapment of the hydrophobic ion pair of PAMB and quaternary ammonium ions in the column; we demonstrated that this color band length correlates quantitatively with the phosphate concentration. In order to optimize the measurement performance, systematic investigations have been carried out for various experimental parameters such as phosphate concentration, preparation conditions of the column packing material, the type of support material (either silica-gel or PVC), the solution feeding conditions (filtration or penetration), and volume of the sample solution. The effects from some co-existing components were also studied for the measurement of real samples.Determination of phosphate concentrations in actual wastewaters was successfully carried out by this method, indicating that the quantification range achievable was of 3-18 mg PO(4) L(-1) without dilution prior to the analysis. No interference was observed from suspended solid (SS) and organic pollutants (COD, TOC) during the wastewater analysis. Because of the simplicity and rapid processing of the samples (not requiring any special instruments) this newly developed method can be applied to the on-site analysis of wastewater. 相似文献
887.
888.
889.
The union exchange of gold from. chloride-nitrate medium is described and applied to the determination of 0.01 to 100 p.p.m.. of gold in copper metal as a separation step before photometry or activation analysis. 相似文献
890.
Tatsuya Shirahata Toshiaki Sunazuka Kiminari Yoshida Daisuke Yamamoto Yoshihiro Harigaya Takayuki Nagai Hiroaki Kiyohara Haruki Yamada Satoshi ōmura 《Tetrahedron》2006,62(40):9483-9496
Pinellic acid from the tuber of Pinellia ternate, an active herbal component of the traditional Japanese herbal (Kampo) medicine Sho-seiryu-to, is a C18 trihydroxy fatty acid whose absolute stereochemistry has now been determined. All stereoisomers of pinellic acid were synthesized via regioselective asymmetric dihydroxylation, regioselective inversion, and stereoselective reduction in order to determine their absolute stereochemistries and adjuvant activities. Among this series of isomers, the (9S,12S,13S)-compound, which is a natural product, exhibited the most potent adjuvant activity. Spectral data for all of the stereoisomers of the 1,2-allylic diols were compared and related to their stereochemistries. 相似文献