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509 results on '"Tamura, Rui"'

23. EPR studies on molecular orientation in a surface-stabilized paramagnetic liquid crystal cell

Author

Noda, Yohei, Shimono, Satoshi, Baba, Masaaki, Yamauchi, Jun, Ikuma, Naohiko, and Tamura, Rui

Subjects
Liquid crystals -- Chemical properties, Liquid crystals -- Research, Electron paramagnetic resonance -- Usage, Benzene -- Chemical properties, Benzene -- Structure, Chemicals, plastics and rubber industries
Abstract

The EPR spectroscopy is used to examine the orientation of paramagnetic liquid crystal (LC) (2S,5S)-2,5-dimetyl-2-heptyloxyphenyl-5-[4-(4-octyloxybenzenecarbonyloxy)phenyl]pyrrolidine-1-oxy molecules in a surface-stabilized liquid crystal (LC) cell. The order parameter is determined by measuring the temperature profile of the g-value and fitted it by use of the Haller equation.

Published
2006

32. A new synthesis of alpha-asymmetric nitroxide radicals

Author

Tamura, Rui, Susuki, Shinsuke, Azuma, Nagao, Matsumoto, Akira, Toda, Fumio, and Ishii, Yasutaka

Subjects
Organic compounds -- Synthesis, Nitrogen compounds -- Analysis, Oxidation-reduction reaction -- Analysis, Biological sciences, Chemistry
Abstract

Nitro-substituted benzoyl chlorides can be used to synthesize alpha-asymmetric bicyclic nitroxide. Reduction of homoallylic nitroenones with SmI2 in THF at -50 degrees celsius produces a nitroxide radical-enolate substrate that, on the inclusion of acyl chloride, causes O-acylation of the enolate to produce the desired product. The reaction mechanism is susceptible to reaction temperature, solvent composition and concentration of SmI2. Analytically pure nitroxide radicals are obtained by using an electron-withdrawing group and benzoyl chloride.

Published
1995

33. Asymmetric synthesis of 3-substituted 2-exo-methylenealkanones by addition-elimination reaction using a chiral leaving group and organometallic nucleophiles

Author

Tamura, Rui, Watabe, Ken-ichiro, Ono, Noboru, and Yamamoto, Yukio

Subjects
Lactones -- Research, Organic compounds -- Synthesis, Organometallic compounds -- Research, Biological sciences, Chemistry
Abstract

The reaction of (S)-2-(2- methoxymethyl -1-pyrrolidinyl -methyl)-2-cyclohexen-1-one and -cyclohepten-1-one with organometals such as lithium diorganocuprates formed 3-substituted 2-methylenecyclohexanones and -heptanones in 95% and 97% enantiomeric excesses, respectively. The process involved a highly diastereodifferentiating addition-elimination asymmetric induction which depended on the type of substrates, organometallic reagents, chiral auxiliaries and Lewis acids employed. Moreover, the process could readily prepare chiral 3-substituted 2-methylenecycloalkanones with high reproducibility.

Published
1992

34. Size-tunable MRI-visible nitroxide-based magnetic mixed micelles: preparation, stability, and theranostic application

Author

Nagura, Kota, primary, Bogdanov, Alexey, additional, Chumakova, Natalia, additional, Vorobiev, Andrey Kh, additional, Moronaga, Satori, additional, Imai, Hirohiko, additional, Matsuda, Tetsuya, additional, Noda, Yohei, additional, Maeda, Tomoki, additional, Koizumi, Satoshi, additional, Sakamoto, Koichi, additional, Amano, Tsukuru, additional, Yoshino, Fumi, additional, Kato, Tatsuhisa, additional, Komatsu, Naoki, additional, and Tamura, Rui, additional

Published
2019
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35. Magnetic Mixed Micelles Composed of a Non-Ionic Surfactant and Nitroxide Radicals Containing a D-Glucosamine Unit: Preparation, Stability, and Biomedical Application

Author

Nagura, Kota, primary, Takemoto, Yusa, additional, Yoshino, Fumi, additional, Bogdanov, Alexey, additional, Chumakova, Natalia, additional, Vorobiev, Andrey, additional, Imai, Hirohiko, additional, Matsuda, Tetsuya, additional, Shimono, Satoshi, additional, Kato, Tatsuhisa, additional, Komatsu, Naoki, additional, and Tamura, Rui, additional

Published
2019
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36. Unique Superparamagnetic‐like Behavior Observed in Non‐π‐delocalized Nitroxide Diradical Compounds Showing Discotic Liquid Crystalline Phase

Author

Takemoto, Yusa, primary, Zaytseva, Elena, additional, Suzuki, Katsuaki, additional, Yoshioka, Naoki, additional, Takanishi, Yoichi, additional, Funahashi, Masahiro, additional, Uchida, Yoshiaki, additional, Akita, Takuya, additional, Park, Jayeong, additional, Sato, Shuichi, additional, Clevers, Simon, additional, Coquerel, Gérard, additional, Mazhukin, Dmitrii G., additional, Shimono, Satoshi, additional, Sugiyama, Masahito, additional, Takahashi, Hiroki, additional, Yamauchi, Jun, additional, and Tamura, Rui, additional

Published
2018
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37. Anisotropic and Inhomogeneous Magnetic Interactions Observed in All-Organic Nitroxide Radical Liquid Crystals

Author

Uchida, Yoshiaki, Suzuki, Katsuaki, Tamura, Rui, Ikuma, Naohiko, Shimono, Satoshi, Noda, Yohei, and Yamauchi, Jun

Abstract

An anisotropic and inhomogeneous magnetic interaction (the average spin−spin interaction constant J̅> 0) was observed in the various liquid crystalline (LC) phases of racemic and nonracemic all-organic radical LC compounds 1aand 1b. We discussed how the LC superstructures induced the magnetic interaction to operate in the LC phases in terms of spin−spin dipole and exchange interactions by means of VT-EPR spectroscopy. The magnitude of the magnetic interaction depended on the type of LC phase, or the superstructure. Furthermore, these radical LC droplets floating on water were commonly attracted to a permanent magnet and moved freely under the influence of this magnet, whereas the crystallized particles of the same compounds never responded to the magnet. The response of the LC droplets to the magnet also varied depending on the type of LC phase, that is, the extent of the magnetic interaction.

Published
2024
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39. Preparation of Robust Metal-Free Magnetic Nanoemulsions Encapsulating Low-Molecular-Weight Nitroxide Radicals and Hydrophobic Drugs Directed Toward MRI-Visible Targeted Delivery

Author

Nagura, Kota, primary, Takemoto, Yusa, additional, Moronaga, Satori, additional, Uchida, Yoshiaki, additional, Shimono, Satoshi, additional, Shiino, Akihiko, additional, Tanigaki, Kenji, additional, Amano, Tsukuru, additional, Yoshino, Fumi, additional, Noda, Yohei, additional, Koizumi, Satoshi, additional, Komatsu, Naoki, additional, Kato, Tatsuhisa, additional, Yamauchi, Jun, additional, and Tamura, Rui, additional

Published
2017
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40. EPR characterization of diamagnetic and magnetic organic soft materials using nitroxide spin probe techniques

Author

Tamura, Rui, Suzuki, Katsuaki, Uchida, Yoshiaki, and Noda, Yohei

Abstract

This review article summarizes the recent advances in the EPR studies of the molecular orientation and magnetic properties in the various rod-like liquid crystalline (LC) phases of the second-generation of organic nitroxide radical materials in the bulk state or in a surface-stabilized LC cell, compared with the conventional EPR studies using classical organic nitroxide spin probes. Noteworthy is the first observation and characterization of a sort of spin glass-like ferromagnetic interactions (J＞0) induced by weak magnetic fields in the various LC phases of the second-generation of organic nitroxide radical materials. This unique magnetic property has been referred to as positive "magneto-LC effects". The utility of such novel LC nitroxide radical materials as the EPR spin probes is also presented., Electron Paramagnetic Resonance (EPR) highlights major developments in this area, with results being set into the context of earlier work and presented as a set of critical yet coherent overviews. The topics covered describe contrasting types of application, ranging from biological areas such as EPR studies of free-radical reactions in biology and medically-related systems, to experimental developments and applications involving EPR imaging, the use of very high fields, and time-resolved methods. Critical and up-to-the-minute reviews of advances involving the design of spin-traps, advances in spin-labelling, paramagnetic centres on solid surfaces, exchange-coupled oligomers, metalloproteins and radicals in flavoenzymes are also included. As EPR continues to find new applications in virtually all areas of modern science, including physics, chemistry, biology and materials science, this series caters not only for experts in the field, but also those wishing to gain a general overview of EPR applications in a given area

Published
2013

41. Stereoselective synthesis of cis 2,3-disubstituted cycloheptanones by kinetic protonation

Author

Tamura, Rui, Watabe, Ken-ichiro, Kamimura, Akio, Hori, Kenzi, and Yokomori, Yoshinobu

Subjects
Organic compounds -- Synthesis, Lactones -- Research, Nuclear magnetic resonance spectroscopy -- Usage, Molecular orbitals -- Research, Biological sciences, Chemistry
Abstract

Thiophenol and lithium diphenylcuprate nucleophiles reacted with 3-substituted 2-methylenecyclohexanones to form cis 2,3-disubstituted cycloheptanones with relatively high stereoselectivity via Michael addition. Structural studies using H nuclear magnetic resonance and X-ray analyses determined the conformations of the resulting compounds. In addition, molecular orbital calculations utilizing Austin model 1 method identified the kinetic protonation of the cycloheptanone product which led to cis selectivity.

Published
1992

42. Azacalix[7]arene heptamethyl ether: preparation, nanochannel crystal structure, and selective adsorption of carbon dioxide

Author

Tsue, Hirohito, Matsui, Kazuhiro, Ishibashi, Koichi, Takahashi, Hiroki, Tokita, Satoshi, Ono, Kohei, and Tamura, Rui

Subjects
Adsorption -- Analysis, Calixarenes -- Chemical properties, Carbon dioxide -- Chemical properties, Ethers -- Chemical properties, Ethers -- Structure, Biological sciences, Chemistry
Abstract

A [5+2]-fragment coupling approach was applied to prepare azacalix[7]arene heptamethyl ether and gain insight into the solid-state complexation of nitrogen-bridged calixarene analogues. The results revealed that the adsorption capacity of azacalix[7]arene for C[O.sub.2] nearly doubled compared to that of azacalix[6]arene due to the formation of the one-dimensional nanochannel with almost twice the volume of the latter.

Published
2008

45. Preparation and characterization of new chiral nitronyl nitroxides bearing a stereogenic center in the Imidazolyl framework

Author

Shimono, Satoshi, Tamura, Rui, Ikuma, Naohiko, Takimoto, Tatsuya, Kawame, Naoyuki, Tamada, Osamu, Sakai, Naoko, Matsuura, Hiroaki, and Yamauchi, Jun

Subjects
Spectrum analysis -- Analysis, Nitro compounds -- Research, Biological sciences, Chemistry
Abstract

A synthetic procedure for optically active and racemic alpha-nitronyl nitroxides is described. The magnetic properties of active and racemic alpha-NNs in solution and in solid state are characterized by EPR spectroscopy and magnetic susceptibility measurement.

Published
2004

47. Mechanism of preferential enrichment, an unusual enantiomeric resolution phenomenon caused by polymorphic transition during crystallization of mixed crystals composed of two enantiomers

Author

Tamura, Rui, Fujimoto, Daisuke, Lepp, Zsolt, Misaki, Kentaro, Miura, Hideyuki, Takahashi, Hiroki, Ushio Takanori, Nakai Tadashi, and Hirotsu Ken

Subjects
Racemization -- Analysis, X-ray crystallography -- Analysis, Chemistry
Abstract

The mechanism of Preferential Enrichment, an unusual enantiomeric resolution phenomenon observed upon recrystallization of a series of racemic crystals which are classified as a racemic mixed crystals with fairly ordered arrangement of the two enantiomers, is studied. Both metastable and stable crystals are obtained, and their crystal structures are elucidated by X-ray crystallographic analysis of their single crystals.

Published
2002

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