Papers - Obata, Rika

Quantum yield improvement of red-light-emitting firefly luciferin analogues for in vivo bioluminescence imaging

Masahiro Kiyama, Satoshi Iwano, Satoshi Otsuka, Shijia W. Lu, Rika Obata, Atsushi Miyawaki, Takashi Hirano, Shojiro A.Maki

Tetrahedron 74 ( 6 ) 652 - 660 2017.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4020

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Discovery of benzo[g]indoles as a novel class of non-covalent Keap1-Nrf2 protein-protein interaction inhibitor

Daisuke Yasuda, Akihiro Yuasa, Rika Obata, Mao Nakajima, Kyoko Takahashi, Tomoyuki Ohe, Yoshinobu Ichimura, Masaaki Komatsu, Masayuki Yamamoto, Riyo Imamura, Hirotatsu Kojima, Takayoshi Okabe, Tetsuo Nagano, Tadahiko Mashino

Bioorganic and Medicinal Chemistry Letters (ELSEVIER)  27 ( 22 ) 5006 - 5009 2017.11

Research paper (scientific journal), Joint Work, Accepted

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Synthesis of Keap1-phosphorylated p62 and Keap1-Nrf2 protein-protein inter- action inhibitors and their inhibitory activity

Daisuke Yasuda, Mao Nakajima, Akihiro Yuasa, Rika Obata, Kyoko Takahashi, Tomoyuki Ohe, Yoshinobu Ichimura, Masaaki Komatsu, Masayuki Yamamoto, Riyo Imamura, Hirotatsu Kojima, Takayoshi Okabe, Tetsuo Nagano, Tadahiko Mashino

Bioorganic and Medicinal Chemistry Letters (ELSEVIER)  26 ( 24 ) 5956 - 5959 2016.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0960-894X

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p62/Sqstm1 promotes malignancy of HCV-positive hepatocellular carcinoma through Nrf2-dependent metabolic reprogramming

Tetsuya Saito, Yoshinobu Ichimura, Keiko Taguchi, Takafumi Suzuki, Tsunehiro Mizushima, Kenji Takagi, Yuki Hirose, Masayuki Nagahashi, Tetsuro Iso, Toshiaki Fukutomi, Maki Ohishi, Keiko Endo, Takefumi Uemura, Yasumasa Nishito, Shujiro Okuda, Miki Obata, Tsuguka Kouno, Riyo Imamura, Yukio Tada, Rika Obata, Daisuke Yasuda, Kyoko Takahashi, Tsutomu Fujimura, Jingbo Pi, Myung-Shik Lee, Takashi Ueno, Tomoyuki Ohe, Tadahiko Mashino, Toshifumi Wakai, Hirotatsu Kojima, Takayoshi Okabe, Tetsuo Nagano, Hozumi Motohashi, Satoshi Waguri, Tomoyoshi Soga, Masayuki Yamamoto, Keiji Tanaka, Masaaki Komatsu

Nature Communications 7 2016.06

Research paper (scientific journal), Joint Work, Accepted

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Multicolor bioluminescence obtained using firefly luciferin

Masahiro Kiyama, Ryohei Saito, Satoshi Iwano, Rika Obata, Haruki Niwa, Shojiro A. Maki

Current Topics in Medicinal Chemistry 16 ( 24 ) 2648 - 2655 2016

Research paper (scientific journal), Joint Work, Accepted

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Crystal structure of 5,5′-dibromo-3,3′-di-tert-butyl-6,6′-dimethylbiphenyl-2,2′-diol

Obata Rika, Ohba Shigeru, Einaga Yasuaki, Nishiyama Shigeru

Acta Crystallographica Section E: Structure Reports Online 71 ( Pt 5 ) o278 - o279 2015.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1600-5368

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<p>The whole molecule of the title compound, C&lt;inf&gt;22&lt;/inf&gt;H&lt;inf&gt;28&lt;/inf&gt;Br&lt;inf&gt;2&lt;/inf&gt;O&lt;inf&gt;2&lt;/inf&gt;, is generated by twofold rotation symmetry. The dihedral angle of the biphenyl moiety is 85.05 (11)°. The hydroxy groups show intramolecular O - H⋯π interactions without any other hydrogen-bond acceptors. In the crystal, there are no other significant intermolecular interactions present.</p>

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Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

Kojima, Taiki, Obata, Rika, Saito, Tsuyoshi, Einaga, Yasuaki, Nishiyama, Shigeru

Beilstein Journal of Organic Chemistry (Beilstein-Institut zur Foerderung der Chemischen Wissenschaften)  11   200 - 203 2015.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1860-5397

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The electroredn. reaction of Me cinnamate on a boron-doped diamond (BDD) electrode was investigated. The hydrodimer, di-Me 3,4-diphenylhexanedioate (racemate/meso = 74:26), was obtained in 85% yield as the major product, along with small amts. of cyclic Me 5-oxo-2,3-diphenylcyclopentane-1-carboxylate. Two new neolignan-type products were synthesized from the hydrodimer.

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Synthesis and luminescence properties of biphenyl-type firefly luciferin analogs with a new, near-infrared light-emitting bioluminophore

Miura Chihiro, Kiyama Masahiro, Iwano Satoshi, Ito Kazuto, Obata Rika, Hirano Takashi, Maki Shojiro, Niwa Haruki

Tetrahedron 69 ( 46 ) 9726 - 9734 2013.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4020

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<p>New firefly luciferin analogs of the 4,4′-substituted biphenyl-type were synthesized. One analog with a 4′-dimethylamino group possessed bioluminescence activity, emitting near-infrared biological window light at 675 nm suitable for deep-site bioimaging of living animals. The chemiluminescence light-emission maximum of the corresponding methyl ester of the bioluminescence active analog was 500 nm, implying that biphenyl and thiazolinone rings in the light emitter might be placed in a coplanar conformation at the polar luciferase active site. © 2013 Elsevier Ltd. All rights reserved.</p>

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Development of simple firefly luciferin analogs emitting blue, green, red, and near-infrared biological window light

Iwano Satoshi, Obata Rika, Miura Chihiro, Kiyama Masahiro, Hama Kazutoshi, Nakamura Mitsuhiro, Amano Yoshiharu, Kojima Satoshi, Hirano Takashi, Maki Shojiro, Niwa Haruki

Tetrahedron (Elsevier Ltd.)  69 ( 19 ) 3847 - 3856 2013.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4020

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<p>Simple firefly luciferin analogs emitting blue, green, and red light were developed. The longest emission maximum was observed at 675 nm, which belongs to the NIR biological window (650-900 nm), useful for deep site bioimaging of living animals. The analogs showed a slow rise of emission intensity compared with the rapid emission of natural luciferin. The light emission of the adenylated analogs was strongly enhanced compared with those of analogs themselves.© 2013 Elsevier Ltd. All rights reserved.</p>

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A new NF-κB inhibitor based on the amino-epoxyquinol core of DHMEQ

Saitoh Tsuyoshi, Shimada Chika, Takeiri Masatoshi, Shiino Mitsuhiro, Ohba Shigeru, Obata Rika, Ishikawa Yuichi, Umezawa Kazuo, Nishiyama Shigeru

Bioorganic and Medicinal Chemistry Letters 20 ( 19 ) 5638 - 5642 2010.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0960-894X

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<p>The amino-epoxyquinols 6a and 6b were synthesized as soluble derivatives of an NF-κB inhibitor DHMEQ (1). In spite of the opposite configuration from 1, 6b rather than 6a affected the deactivation of NF-κB, based on NO secretion and MALDI-TOF MS analysis. It was indicated that 6b inhibited the activation by different manner from that of 1. © 2010 Elsevier Ltd. All rights reserved.</p>

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Synthesis of Epoxyquinols via Anodic Oxidation and Evaluation of NF-κB Inhibitory Activity.

Takeshi Saitoh, Eriko Suzuki, Arisa Takasugi, Rika Obata, Yuichi Ishikawa, Kazuo Umezawa, Shigeru Nishiyama

ECS Meeting Abstract, 217th ECS Meeting (The Electrochemical Society)  MA2010-01 2010.04

Research paper (international conference proceedings), Joint Work

Structural basis for inverting the enantioselectivity of arylmalonate decarboxylase revealed by the structural analysis of the Gly74Cys/Cysl88Ser mutant in the liganded form

Obata Rika, Nakasako Masayoshi

Biochemistry (American Chemical Society)  49 ( 9 ) 1963 - 1969 2010.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0006-2960

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<p>Arylmalonate decarboxylase catalyzes the enantioselective decarboxylation of α-aryl-α-methylmalonate to produce optically pure α-arylpropionate. The enzyme is comprised of two α/β domains and contains an active site situated between the two domains. The site is formed by Tyr48, Gly74-Thr75-Ser76, Tyr126, and Cys188-Gly189-Gly190 residues. Since it has been observed that the Gly74Cys/Cys188Ser mutation inverts the enantioselectivity of the enzyme, we determined the crystal structure of the Gly74Cys/ Cys188Ser mutant in the liganded form at a resolution of 1.45 Å to understand the structural basis for this inversion. The overall structure of the enzyme overlapped well with that of the benzylphosphonate-associated wild-type enzyme, and the mutations had little effect on the structure of the active site. A ligand molecule bound to the active site in an unusual semiplanar conformation resembling the planar enediolate reaction intermediate could be assigned as phenyl acetate. The inversion in enantioselectivity by the paired mutation is explained by the mirror symmetry between Cys74 in the mutant and Cys188 of the wild type with respect to the carbon atom in the ligand to be protonated. Comparison of the wild-type and Gly74Cys mutant crystal structures suggested that ligand binding induces a positional shift of the Cys188-Gly189-Gly190 region toward the Gly74-Thr75 pair which provides two oxyanion holes necessary to stabilize the negatively charged enediolate reaction intermediate. The ligand binding also simultaneously induces the formation of a hydrophobic cluster over the active site cleft. Thus, AMDase is proposed to have "open" and "closed" conformations of the active site that are regulated by ligand binding. These results may provide an effective strategy for the rational design to invert the enantioselectivity of enzymes. © 2010 American Chemical Society.</p>

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Efficient synthesis of (±)-parasitenone, a novel inhibitor of NF-κB.

Saitoh Tsuyoshi, Suzuki Eriko, Takasugi Arisa, Obata Rika, Ishikawa Yuichi, Umezawa Kazuo, Nishiyama Shigeru

Bioorganic and Medicinal Chemistry Letters 19 ( 18 ) 5383 - 5386 2009.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0960-894X

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<p>Dehydroxymethylepoxyquinomicin (DHMEQ, 1) is a novel nuclear factor-κB (NF-κB) inhibitor that inhibits DNA binding of NF-κB components including p65. To inspect its biological activity of 1, we synthesized parasitenone (3), possessing the common epoxycyclohexenone moiety of 1. Assessment of the inhibitory activity against NF-κB indicated that the epoxycyclohexenone moiety is the most essential element for the NF-κB inhibitory activity and the salicylic acid moiety may contribute the binding efficiency and specificity. © 2009 Elsevier Ltd. All rights reserved.</p>

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Synthesis and biological evaluation on novel analogs of 9-methylstreptimidone, an inhibitor of NF-κB.

Ishikawa Yuichi, Tachibana Miyuki, Matsui Chino, Obata Rika, Umezawa Kazuo, Nishiyama Shigeru

Bioorganic and Medicinal Chemistry Letters (Elsevier B.V.)  19 ( 6 ) 1726 - 1728 2009.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0960-894X

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<p>Synthesis of 9-methylstreptimidone analogs and their inhibitory activities against NF-κB (nuclear factor-κB) are reported. Among several active derivatives synthesized in this study, 8 with a relatively simple structure, exhibited inhibitory activity against LPS-induced NO production comparable to that of 9-methylstreptimidone. © 2009 Elsevier Ltd. All rights reserved.</p>

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Crystallization and preliminary X-ray diffraction experiments of arylmalonate decarboxylase from Alcaligenes bronchisepticus

Nakasako Masayoshi, Obata Rika, Okubo Ryosuke, Nakayama Shyuichi, Miyamoto Kenji, Ohta Hiromichi

Acta Crystallographica Section F: Structural Biology and Crystallization Communications (International Union of Crystallography)  64 ( 7 ) 610 - 613 2008.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1744-3091

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<p>Arylmalonate decarboxylase catalyses the enantioselective decarboxylation of α-aryl-α-methylmalonates to produce optically pure α-arylpropionates. The enzyme was crystallized with ammonium sulfate under alkaline pH conditions with the aim of understanding the mechanism of the enantioselective reaction. X-ray diffraction data collected to a resolution of 3.0 Å at cryogenic temperature showed that the crystals belonged to the orthorhombic space group P212121, with unit-cell parameters a = 83.13, b = 99.62, c = 139.64 Å. This suggested that the asymmetric unit would contain between four and six molecules. Small-angle X-ray scattering revealed that the enzyme exists as a monomer in solution. Thus, the assembly of molecules in the asymmetric unit was likely to have been induced during the crystallization process. © International Union of Crystallography 2008.</p>

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Synthesis of pinguisane-type sesquiterpenoids acutifolone A, pinguisenol, and bisacutifolones by a Diels-Alder dimerization reaction

Shiina Junichi, Oikawa Masataka, Nakamura Kensuke, Obata Rika, Nishiyama Shigeru

European Journal of Organic Chemistry (Wiley-VCH Verlag GmbH & Co. KGaA)   ( 31 ) 5190 - 5197 2007.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1434-193X

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<p>The total synthesis of pinguisane-type sesquiterpenoids, acutifolone A (1) and pinguisenol (2), has been achieved by using the Mukaiyama aldol reaction as the key step. The intermolecular Diels-Alder reaction of these monomelic natural products successfully led to stereoselective dimerization, leading to bisacutifolones A (3) and B (4). Theoretical calculations revealed that the dimerization reaction proceeded through the most stable transition state. © Wiley-VCH Verlag GmbH &amp; Co. KGaA, 2007.</p>

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Bacillus subtilis epoxide hydrolase-catalyzed preparation of enantiopure 2-methylpropane-1,2,3-triol monobenzyl ether and its application to expeditious synthesis of (R)-bicalutamide

Fujino Aya, Asano Masayoshi, Yamaguchi Hitomi, Shirasaka Naoki, Sakoda Akiko, Ikunaka Masaya, Obata Rika, Nishiyama Shigeru, Sugai Takeshi

Tetrahedron Letters 48 ( 6 ) 979 - 983 2007.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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<p>Expeditious synthesis of (R)-bicalutamide (1), a synthetic antiandrogen, from enantiopure 2-methylpropane-1,2,3-triol monobenzyl ether (4) was achieved. An engineered Bacillus subtilis epoxide hydrolase worked enantioselectively on the racemic epoxide (7) to provide the above starting material in highly enantiomerically enriched state. © 2006 Elsevier Ltd. All rights reserved.</p>

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Screening, substrate specificity and stereoselectivity of yeast strains, which reduce sterically hindered isopropyl ketones

Hiraoka Chihiro, Matsuda Masaaki, Suzuki Yuya, Fujieda Shigeo, Tomita Mina, Fuhshuku Ken ichi, Obata Rika, Nishiyama Shigeru, Sugai Takeshi

Tetrahedron Asymmetry 17 ( 24 ) 3358 - 3367 2006.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0957-4166

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<p>Towards the synthesis of sterically hindered optically active secondary alcohol 2, yeast strains (Candida floricola IAM 13115 and Trichosporon cutaneum IAM 12206) with si-face hydride attack on isopropyl phenylsulfonylmethyl ketone 1 were developed by screening. Strains with complementary re-facial selectivity (Pichia angusta IAM 12895 and Pichia minuta IAM 12215) were also found. Based on the substrate specificity studies of these four strains, microbial reduction was applied to the synthesis of (3S,5S)-2,6-dimethyl-3,5-heptanediol 12a. © 2007 Elsevier Ltd. All rights reserved.</p>

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Oxidative cyclization of isodityrosine tripeptides: Optimized condition and application of electrochemically generated thallium(III) ion

Tanabe Takamasa, Obata Rika, Nishiyama Shigeru

Heterocycles (Japan Institute of Heterocyclic Chemistry)  69 ( 1 ) 113 - 118 2006.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0385-5414

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<p>Thallium(III) trinitrate oxidation of the tripeptide, which was a synthetic precursor of the 17-membered isodityrosine natural product, eurypamide, was investigated to give the desired cyclized compound in 96% yield at best. In addition, the thallium(III) species generated by electrochemical oxidation of thallium(I) successfully produced the target compounds. © 2006 The Japan Institute of Heterocyclic Chemistry.</p>

Synthesis of chiloscyphones and the biological activities of their synthetic intermediates against methicillin-resistant Staphylococcus aureus (MRSA)

Shiina Junichi, Obata Rika, Tomoda Hiroshi, Nishiyama Shigeru

European Journal of Organic Chemistry  ( 10 ) 2362 - 2370 2006.05

Research paper (scientific journal), Joint Work,  ISSN  1434-193X

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<p>The total syntheses of chiloscyphone (1) and isochiloscyphone (2) have been achieved. Furthermore, the synthetic intermediate 5 shows biological activity against methicillin-resistant Staphyrococcus aureus, and compounds 5, 17, and 18, display imipenem-type activity. The tricyclic lactone framework, which includes an α,β-unsaturated ketone moiety, might play a crucial role in the anti-MRSA activity. © Wiley-VCH Verlag GmbH &amp; Co. KGaA, 2006.</p>

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