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991.
Shingo Atobe Haruna Masuno Motohiro Sonoda Yuki Suzuki Hiroyuki Shinohara Satoshi Shibata Akiya Ogawa 《Tetrahedron letters》2012,53(14):1764-1767
In the presence of 1-(2-pyridylethynyl)-2-(2-thienylethynyl)benzene as a ligand, the direct synthesis of alkynones has accomplished by a Pd-catalyzed coupling reaction of acid chlorides with terminal acetylenes under mild conditions. 相似文献
992.
993.
Heon-Jung Kim M. SasakiA. Ohnishi M. KitauraM. Saito S. NonoyamaY. Hara K. Ogawa 《Physica B: Condensed Matter》2012,407(1):126-130
The magnetic properties of β-FeSi2 single crystals were investigated using magnetization and anomalous Hall effect measurements. These measurements clearly show the appearance of superparamagnetism, the origin of which is attributed to defect-induced magnetic aggregates. Unlike previous reports, based on our combined analysis using magnetization and the anomalous Hall effect, we found that two kinds of aggregates, which are magnetically distinct, exist in our samples. Among the two types found, one gives an anomalous Hall term, which follows a side-jump mechanism while the other is a completely new kind, suggesting that magnetic properties of β-FeSi2 are very unconventional. The sizes of the aggregates were estimated from our experimental data. 相似文献
994.
995.
996.
997.
PyBidine–Cu(OTf)2‐Catalyzed Asymmetric [3+2] Cycloaddition with Imino Esters: Harmony of Cu–Lewis Acid and Imidazolidine‐NH Hydrogen Bonding in Concerto Catalysis 下载免费PDF全文
Prof. Dr. Takayoshi Arai Hiroki Ogawa Dr. Atsuko Awata Dr. Makoto Sato Megumi Watabe Prof. Dr. Masahiro Yamanaka 《Angewandte Chemie (International ed. in English)》2015,54(5):1595-1599
A bis(imidazolidine)pyridine (PyBidine)–Cu(OTf)2 complex catalyzing the endo‐selective [3+2] cycloaddition of nitroalkenes with imino esters was applied to the reaction of methyleneindolinones with imino esters to afford spiro[pyrrolidin‐3,3′‐oxindole]s in up to 98 % ee. X‐ray crystallographic analysis of the PyBidine–Cu(OTf)2 complex and DFT calculations suggested that an intermediate Cu enolate of the imino ester reacts with nitroalkenes or methyleneindolinones, which are activated by NH‐hydrogen bonding with the PyBidine–Cu(OTf)2 catalyst. 相似文献
998.
Maresin 1 (with the 7R carbon) and (7S)-maresin 1 were synthesized stereoselectively. The conjugated triene system was constructed by Pd-catalyzed coupling of the trans cis-dienylborane (the C10–C22 part) with the trans vinyl iodide corresponding to the C1–C9 part. The stereogenic centers at C7 and C14 were created by Ru-catalyzed asymmetric reduction of ketone and asymmetric epoxidation/kinetic resolution of the racemic alcohol, respectively. 相似文献
999.
A fiber-packed needle was developed as a novel extraction device for gas-chromatographic analysis of trace organic compounds
in aqueous samples. In the extraction device, a bundle of the polymer-coated filaments as the sorbent material was longitudinally
packed into a specially designed needle. The extraction was made by pumping the aqueous sample solution into the needle extraction
device, and the subsequent desorption process was carried out with a flow of desorption solvent through the needle in a heated
gas chromatograph injector. The needle device showed an excellent thermal stability for repeated use without any deterioration
of extraction performance, and no carryover effect was observed after the optimization of the desorption conditions. Additionally,
the extraction efficiency of the fiber-packed needle could be enhanced by optimizing the number of packed filaments. The selectivity
for various compounds could be also tuned using an appropriate combination of the fibrous medium and the coating polymer.
The relative standard deviation for run to run was from 3.88 to 4.55% (n = 5), and that for needle to needle was 7.21% (n = 3), clearly suggesting a good repeatability of the needle extraction technique developed. Upon successful optimization
of the extraction conditions, a rapid extraction of trace organic compounds from an aqueous sample matrix was successfully
demonstrated, where each extraction process was completed within 10 min. 相似文献
1000.
Ogawa S Hosoi K Ikeda N Makino M Fujimoto Y Iida T 《Chemical & pharmaceutical bulletin》2007,55(2):247-250
Oxyfunctionalization of the bioactive terpenoids, ursolic acid acetate (1), oleanolic acid acetate (5), lupeol acetate (12), and kaurenic acid (17), with dimethyldioxirane (DMDO) was investigated. Treatment of the terpenoids with DMDO under mild conditions afforded a variety of oxidation and oxydegradation products to yield naturally occurring and/or novel compounds in one step. After chromatographic separation, the structures of the individual isolated products were determined using spectroscopic methods including several homonuclear (1H-1H) and heteronuclear (1H-13C) shift-correlated 2D-NMR techniques. The inhibitory activity of the terpenoid derivatives against alpha-glucosidase was investigated and compounds 1, 3, 7, and 9 were found to exhibit potent activity. 相似文献