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41.
Motohiro Akazome Toshiaki Takahashi Ryo-Ichi Sonobe Katsuyuki Ogura 《Supramolecular chemistry》2013,25(1):109-136
Abstract Crystallization of (R)-(1-naphthyl)glycyl-(R)-phenyl-glycine [(R,R)-1] in the presence of oligo(ethylene glycol) dimethyl ethers 2(n) or poly(ethylene glycol)s (PEGs, 3(Mn )) afforded inclusion compounds. The ratio of (R,R)-1/the guest polymer (2 or 3) was proportional to the length of the polymer chain. The crystal structure of a hepta(ethylene glycol) dimethyl ether-included compound was disclosed by X-ray crystallography which showed that (R,R)-1 molecules form a sheet and the guest molecule penetrates the crystal lattice of (R,R)-1 through a one-dimensional channel on the sheet. Powder X-ray analysis revealed that, regardless of the length of the guest polymer, the distance between the neighboring sheets remains unchanged (12.0–12.3 Å) in these inclusion crystals. By thermal analysis, it was shown that the decomposition points of these inclusion compounds became higher with the longer PEG included. The inclusion phenomenon enabled the fractionation of PEGs with various molecular weights, among which longer PEG was preferably included. 相似文献
42.
The formation of carbon-carbon bond by sulfur extrusion such as pyrolysis of cyclic sulfones is well known as an important synthetic method, especially for the synthesis of cyclophane framework.1) Little is known about selenium extrusion as the counterpart, though organoseleniums have been properly appreciated as a useful tool for manipulating a functional group.2) Lardon reported that the thermal decomposition of dibenzyl diselenide led to a mixture of dibenzyl selenide and polyselenides.3) In contrast, recent reports showed that at 210°C, heating bis(diphenylmethyl) diselenide resulted in ready selenium extrusion to 1,1,2,2-tetraphenylethane4), and dianthrylmethyl mono- and diselenides to 1,2-dianthrylethane.5) Therefore,- it is worthwhile to study the thermal behavior of dibenzyl selenide itself. 相似文献
43.
We propose and demonstrate generation of an in-phase optical pulse train from an optical beat signal. The proposed method is based on four-wave mixing occurring between the two continuous waves of the beat signal and on spectral filtering to shape the spectrum to be symmetric about the carrier frequency. We perform an experiment to verify the proposed method and obtain a 1.5 ps width in-phase pulse train from a 160 GHz beat signal. Furthermore, we employ a pulse compression scheme to reshape and compress the obtained pulse train, and we show that a 160 GHz repeating, 0.7 ps FWHM, nearly transform-limited, in-phase sech pulse train is successfully generated. 相似文献
44.
Total Synthesis of the Antibiotic Kendomycin: A Macrocyclization Using the Tsuji–Trost Etherification 下载免费PDF全文
Dr. Tetsuya Sengoku Dr. Shu Xu Kenji Ogura Yoshinori Emori Kenji Kitada Prof. Dr. Daisuke Uemura Prof. Dr. Hirokazu Arimoto 《Angewandte Chemie (International ed. in English)》2014,53(16):4213-4216
A highly stereocontrolled, convergent total synthesis of kendomycin [(?)‐TAN2162], an ansa‐macrocyclic antibiotic, is reported. The key of the strategy is an unprecedented Tsuji–Trost macrocyclic etherification, followed by a transannular Claisen rearrangement to construct the 18‐membered carbocyclic framework. The oxa‐six‐ and five‐membered rings were also stereoselectively constructed respectively by a cascade oxidative cyclization at an unfunctionalized benzylic position and using a one‐pot epoxidation/5‐exo‐tet epoxide opening. 相似文献
45.
Jie Zhu Dr. Ryota Osuga Prof. Ryo Ishikawa Prof. Naoya Shibata Prof. Yuichi Ikuhara Prof. Junko N. Kondo Prof. Masaru Ogura Prof. Jihong Yu Prof. Toru Wakihara Prof. Zhendong Liu Prof. Tatsuya Okubo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19837-19842
Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. 相似文献
46.
Raku Watanabe Dr. Nobuki Kato Kengo Hayashi Sho Tozawa Dr. Yusuke Ogura Prof. Shigefumi Kuwahara Prof. Minoru Ueda 《ChemistryOpen》2020,9(10):1008-1017
An efficient and stereoselective syntheses of all the possible stereoisomers of coronafacic acid (CFA) has been developed. The stereochemistries of C3a and C7a were controlled in a diastereoselective Diels-Alder type cycloaddition using a chiral auxiliary. CFA and 6-epi-CFA were synthesized by hydrogenation of a common intermediate. During the synthesis of 6-epi-CFA, we established that its cis-fused configuration is important for the introduction of C4-C5 double bond by dehydration. This report is the first practical synthesis of both 6-epi-CFA, and its enantiomer. 相似文献
47.
Sato S Ogura Y Miyanaga A Sugimoto T Tanaka K Moriyama H 《Journal of chromatography. A》2002,956(1-2):53-58
Ion chromatography (IC) has been a powerful tool for measuring ionic species in environmental samples such as tap, river and drain waters. Suppressor modules (membrane and disposable column types) have been used for reducing the background of a baseline. A new type of suppressor device, which has a suppressor resin and switching valve was developed. Fresh ionic resin is introduced into a groove for each analysis to perform the suppression of the working eluent. The eluent composition for obtaining higher sensitivity and better resolutions among ionic species and carbonate ion was also investigated. Although carbonate buffers are used for ion separation in general, the separation of carbonate ion from other ions was not achieved. A borate eluent resulted in good resolutions and higher sensitivity. A new column was also developed for obtaining higher column efficiency and resolution. The optimization of anion separation using a new IC system (IC-2001) that consists of a new suppressor device, an anion-exchange column (TSKgel SuperIC-Anion, 150x4.6 mm), an autosampler, a conductivity cell and a pump in a compact module is described. 相似文献
48.
It is shown that a square invariant of the Weyl conformal curvature tensor can lead to a Lagrangian in a variational principle for a gravitational equation in vacuum of the Bianchi identity type which is compatible with the Einstein equation. Moreover we show that such a Lagrangian implicitly includes a conformally invariant theory characterized by two gauge fields and the metric tensor. 相似文献
49.
Zearalenone was synthesized by a general cyclization method of orsellic acid type macrolides having ketone moiety using the intramolecular alkylation of the protected cyanohydrin. This alkylation tolerates the presence of ester group and requires short reaction time. 相似文献
50.
The fine structure of polyethylene film has been investigated by using a high-resolution scanning electron microscope equipped with a field emission source. The original film surface of a-axis-oriented blown polyethylene film and the surface of a necked region formed by drawing the film in the machine direction were observed. High magnification electron micrographs indicate that the basic unit of internal texture of this film consists of piled-lamellae units, each pile containing three to ten lamellar crystal sheets. The piled-lamellae unit acts as one body and does not separate into single lamellae during deformation. Many tie fibrils are formed between adjacent piled-lamellae units, when the film is drawn in the machine direction. Although little attention has been given to this mechanism, it is important in deformation. This fact seems to be reflected in different shapes of the stress-strain curves of films drawn the machine direction and perpendicular to it. 相似文献