研究者業績

石川 紘輝

Hiroki Ishikawa

基本情報

所属
千葉大学 西千葉地区事務部理工系総務課技術グループ 技術職員
学位
博士(工学)(千葉大学)

研究者番号
40938247
J-GLOBAL ID
202101021294561715
researchmap会員ID
R000028837

研究キーワード

 3

論文

 20
  • Kazutaka Sanada, Aoi Washio, Hiroki Ishikawa, Yasushi Yoshida, Takashi Mino, Masami Sakamoto
    Angewandte Chemie - International Edition 61(19) 2022年5月2日  
    We developed a chiral symmetry breaking method for monoacylated meso diols. The X-ray crystal structure analysis of monoacylated 1,4-anhydroerythritols, meso cyclic diols with a cis configuration, revealed that the O-(p-anisoyl) derivative crystallized as a racemic conglomerate of the P212121 crystal system. It was confirmed that the substrate racemized by intramolecular transfer of the acyl group in the presence of a catalytic amount of base. Evaporating the solvent gradually from the solution or Viedma ripening to promote crystallization-induced deracemization efficiently led to enantiomer crystals. These results provide the first successful example of asymmetric expression and amplification by deracemization of sugar derivatives without an external chemical chiral source. Furthermore, we applied this methodology to acyclic meso-1,2-diols. Three O-monoacylated substrates were successfully deracemized to 99 % ee by Viedma ripening. We also developed asymmetric desymmetrization of meso-1,2-diols by combining acylation and crystallization-induced deracemization.
  • Kazutaka Sanada, Aoi Washio, Hiroki Ishikawa, Yasushi Yoshida, Takashi Mino, Masami Sakamoto
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2022年3月  
    We developed a chiral symmetry breaking method for monoacylated meso diols. The X-ray crystal structure analysis of monoacylated 1,4-anhydroerythritols, meso cyclic diols with a cis configuration, revealed that the O-(p-anisoyl) derivative crystallized as a racemic conglomerate of the P2(1)2(1)2(1) crystal system. It was confirmed that the substrate racemized by intramolecular transfer of the acyl group in the presence of a catalytic amount of base. Evaporating the solvent gradually from the solution or Viedma ripening to promote crystallization-induced deracemization efficiently led to enantiomer crystals. These results provide the first successful example of asymmetric expression and amplification by deracemization of sugar derivatives without an external chemical chiral source. Furthermore, we applied this methodology to acyclic meso-1,2-diols. Three O-monoacylated substrates were successfully deracemized to 99 % ee by Viedma ripening. We also developed asymmetric desymmetrization of meso-1,2-diols by combining acylation and crystallization-induced deracemization.
  • Takumi Nakamura, Hiroki Ishikawa, Kazuma Ban, Yasushi Yoshida, Takashi Mino, Yoshio Kasashima, Masami Sakamoto
    CHEMPLUSCHEM 87(1) 2022年1月  
    Atroposelective resolution for axially chiral nicotinamides was achieved by dynamic chiral salt formation with L-DBTA using six types of nicotinamides that could not be optically resolved by the preferential crystallization method. Kinetic studies of their racemization indicated that the chiral conformation was retained for a significant period of time. Two methods of crystallization-induced asymmetric transformation were examined by dynamic diastereomeric salt formation: solvent evaporation from a supersaturated solution, and attrition-enhanced asymmetric transformation. The attrition method was more effective for asymmetric amplification of diastereomeric salts of axially chiral materials. Attrition of equimolar amount of the nicotinamide salts with L-DBTA converged to one diastereomer salts, and the corresponding enantiomers in 87-99 % ee were obtained after the chiral acid was removed. Changing the ratio of two of the nicotinamides with L-DBTA to 1 : 2 inverted the axial chirality.
  • Takumi Nakamura, Hiroki Ishikawa, Kazuma Ban, Yasushi Yoshida, Takashi Mino, Yoshio Kasashima, Masami Sakamoto
    ChemPlusChem 87(1) 2022年1月  
    Atroposelective resolution for axially chiral nicotinamides was achieved by dynamic chiral salt formation with L-DBTA using six types of nicotinamides that could not be optically resolved by the preferential crystallization method. Kinetic studies of their racemization indicated that the chiral conformation was retained for a significant period of time. Two methods of crystallization-induced asymmetric transformation were examined by dynamic diastereomeric salt formation: solvent evaporation from a supersaturated solution, and attrition-enhanced asymmetric transformation. The attrition method was more effective for asymmetric amplification of diastereomeric salts of axially chiral materials. Attrition of equimolar amount of the nicotinamide salts with L-DBTA converged to one diastereomer salts, and the corresponding enantiomers in 87–99 % ee were obtained after the chiral acid was removed. Changing the ratio of two of the nicotinamides with L-DBTA to 1 : 2 inverted the axial chirality.
  • Tomofumi Kato, Yasuhiro Yamada, Yasushi Nishikawa, Hiroki Ishikawa, Satoshi Sato
    Carbon 178 58-80 2021年6月  査読有り
    Carbonization process of pyromellitic dianhydride (PMDA)-4,4'-diaminodiphenyl ether (ODA)-type polyimide has been studied for decades. However, various reaction mechanisms have been proposed and the detailed mechanisms are still controversial. It is essential to understand the carbonized structures of PMDA-ODA-type polyimide before analyzing the defect structures in graphite. In this work, the carbonization mechanisms of polyimide heated at 1273 K or lower were unveiled and the methodology to analyze carbon materials containing nitrogen, oxygen, pentagons, and heptagons using computational spectral analysis combined with molecular dynamics simulation (ReaxFF) are exhibited. For example, the formations of isoimide and cyclic ether were estimated by ReaxFF, and the presence was supported by experimental and calculated X-ray photoelectron spectroscopy (XPS) and carbon-13 nuclear magnetic resonance (C-13 NMR) spectra of polyimide heated between 813 and 873 K. The formations of pentagons and heptagon, suggested by ReaxFF, were also supported by Raman and C-13 NMR spectra of polyimide heated between 833 and 1273 K. This work also revealed that the previously reported structures were unstable and that amine in the basal plane was the most plausible structure in polyimide heated at 1073 K or higher, as clarified by XPS, ReaxFF, and the energy calculation. (C) 2021 Elsevier Ltd. All rights reserved.

MISC

 8