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41.
Tsukiho Hayashi Ayumi Osawa Takehiro Watanabe Yoshiko Murata Atsushi Nakayama Kosuke Namba 《Tetrahedron letters》2017,58(20):1961-1964
1,3a,6a-Triazapentalene (TAP)-labeled enterobactin was developed as an iron ion sensor. 3-Acetylated-TAP was successfully introduced to the catechol ring of enterobactin, a well-recognized siderophore secreted by various Gram-negative bacteria. The fluorescence of TAP-labeled enterobactin decreased gradually as the amount of Fe3+ ion as an additive was increased, and 1.2 equiv of Fe3+ ion completely quenched the fluorescence. In clear contrast, when other metal ions were used, the fluorescence of TAP-labeled enterobactin remained even at 5.0 equiv. 相似文献
42.
Osuga T Murase T Ono K Yamauchi Y Fujita M 《Journal of the American Chemical Society》2010,132(44):15553-15555
Three-dimensional m × n arrays of metal ion clusters can be assembled as aromatic stacks of planar polynuclear metal complexes within columnar coordination cages. The polynuclear complexes and cage height program the final array structures of the metal ion clusters. Cyclic trinuclear Au(I) complexes (m = 3) assembled into trigonal prismatic arrays (n = 1-3) within the cages and the array structures were clearly shown by X-ray crystallographic analysis. A silver-sandwiched hetero-Au(3)-Ag-Au(3) cluster was also prepared by treating a hexanuclear Au(3)-Au(3) cluster with Ag(I) ion. 相似文献
43.
Selective oxidation of alcohols catalyzed by novel carbon-stabilized polymer-incarcerated bimetallic nanocluster catalysts using molecular oxygen has been developed. The reactivity and the selectivity were strongly dependent on the combination of metals and solvent systems; aldehydes and ketones were obtained by the gold/platinum catalyst in benzotrifluoride, and esters were formed by the gold/palladium catalyst in methanol. To the best of our knowledge, this is the first example that the reaction pathway has been changed dramatically in gold catalysis by combining with a second metal. The differences in the activity and the selectivity are considered to be derived from the difference in the structure of the bimetallic clusters. 相似文献
44.
The synthesis of various trifluoromethylated amino compounds was studied using trifluoroacetaldehyde, an industrial bulk material, as a starting compound. One general application of trifluoroacetaldehyde is the preparation of trifluoroethylamino derivatives via reductive amination reaction. This synthesis includes the formation of the corresponding N,O-acetal intermediates followed by their reduction using NaBH4 or 2-picoline borane complex, affording the target trifluoroethylamino compounds in moderate to good yields (47-87%).Another general application of trifluoroacetaldehyde is the synthesis of chiral α-substituted trifluoroethylamino compounds. In this synthesis, trifluoroacetaldehyde was first converted into the chiral trifluoromethyl tert-butyl sulfinimine, which was subjected to 1,2-nucleophilic addition reactions across its CN double bond. The addition of phenyllithium afforded α-(phenyl)trifluoroethylamino derivative in 83% yield and with 96% de. Allylation and Reformatsky reactions produced the corresponding α-substituted trifluoroethylamino derivatives in 82 and 58% yields and with 90 and 91% de, respectively. 相似文献
45.
High-Quality Protein Crystal Growth of Mouse Lipocalin-Type Prostaglandin D Synthase in Microgravity
Inaka K Takahashi S Aritake K Tsurumura T Furubayashi N Yan B Hirota E Sano S Sato M Kobayashi T Yoshimura Y Tanaka H Urade Y 《Crystal growth & design》2011,11(6):2107-2111
Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) catalyzes the isomerization of PGH(2) to PGD(2) and is involved in the regulation of pain and of nonrapid eye movement sleep and the differentiation of male genital organs and adipocytes, etc. L-PGDS is secreted into various body fluids and binds various lipophilic compounds with high affinities, acting also as an extracellular transporter. Mouse L-PGDS with a C65A mutation was previously crystallized with citrate or malonate as a precipitant, and the X-ray crystallographic structure was determined at 2.0 ? resolution. To obtain high-quality crystals, we tried, unsuccessfully, to crystallize the C65A mutant in microgravity under the same conditions used in the previous study. After further purifying the protein and changing the precipitant to polyethylene glycol (PEG) 8000, high-quality crystals were grown in microgravity. The precipitant solution was 40% (w/v) PEG 8000, 100 mM sodium chloride, and 100 mM HEPES-NaOH (pH 7.0). Crystals grew on board the International Space Station for 11 weeks in 2007, yielding single crystals of the wild-type L-PGDS and the C65A mutant, both of which diffracted at around 1.0 ? resolution. The crystal quality was markedly improved through the use of a high-viscosity precipitant solution in microgravity, in combination with the use of a highly purified protein. 相似文献
46.
47.
Yasuharu Yoshimi Kosuke Kobayashi Keisuke Nishikawa Kousuke Maeda Tatsuya Itou Minoru Hatanaka 《Tetrahedron letters》2010,51(17):2332-6179
Radical addition to a glyoxylic oxime ether was accomplished under mild conditions using an alkyl radical generated from a free carboxylic acid via photochemical decarboxylation. The photoreaction provided an efficient route to α-substituted α-aminoesters from carboxylic acids and oxime ether. 相似文献
48.
49.
Jun-ichi Matsuo Ryosuke Okuno Kosuke Takeuchi Mizuki Kawano Hiroyuki Ishibashi 《Tetrahedron letters》2010,51(29):3736-3737
Optimized reaction conditions for the preparation of various 2-monosubstituted 3-ethoxycyclobutanones are described. 2-Monoalkyl 3-ethoxycyclobutanones were efficiently prepared by the reaction of the corresponding carboxylic acid chlorides and an excess amount of ethyl vinyl ether in the presence of diisopropylethylamine at 90 °C in a sealed tube. 2-Monoaryl 3-ethoxycyclobutanones were prepared by using 2,6-lutidine as a base in the above-mentioned procedure. 相似文献
50.