Epalrestat tetrahydrofuran monosolvate: Crystal structure and phase transition Umeda Daiki

Daiki Umeda, Okky Dwichandra Putra, Mihoko Gunji, Kaori Fukuzawa, Etsuo Yonemochi

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4 Citations (Scopus)


The title compound, epalrestat {systematic name: (5Z)-5-[(2E)-2-methyl-3-phenylprop-2-en-1-ylidene]-4-oxo-2-sulfanylidene-1,3-Thiazolidine-3-Acetic acid}, crystallized as a tetrahydrofuran monosolvate, C15H13NO3S2·C4H8O. Epalrestat, an important drug for diabetic neuropathy, has been reported to exist in polymphic, solvated and co-crystal forms. In the molecule reported here, the phenyl ring is inclined to the rhodamine ring by 22.31 (9)°, and the acetic acid group is almost normal to the rhodamine ring, making a dihedral angle of 88.66 (11)°. In the crystal, pairs of O-H·O hydrogen bonds are observed between the carboxylic acid groups of epalerstat molecules, forming inversion dimers with an R 2 2(8) loop. The dimers are linked by pairs of C-H·O hydrogen bonds, forming chains along [101]. The solvate molecules are linked to the chain by a C-H·O(tetrahydro furan) hydrogen bond. A combination of thermal analysis and powder X-ray diffraction revealed that title compound desolvated into epalerstat Form II. One C atom of the tetrahydrofuran solvate molecule is positionally disordered and has a refined occupancy ratio of 0.527 (18):0.473 (18).

Original languageEnglish
Pages (from-to)941-944
Number of pages4
JournalActa Crystallographica Section E: Crystallographic Communications
Publication statusPublished - 2017


  • crystal structure
  • epalerstat
  • hydrogen bonding
  • monosolvate
  • tetrahydrofuran


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