A new solvate of epalerstat, a drug for diabetic neuropathy

Epalerstat {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 an acetone monosolvate, C(15)H(13)NO(3)S(2)·C(3)H(6)O. In the epalerstat mol­ecule, the methyl­propyl­enediene moiety is inclined to the phenyl ring and the five-membered rhodamine ring by 21.4 (4) and 4.7 (4)°, respectively. In addition, the acetic acid moiety is found to be almost normal to the rhodamine ring, making a dihedral angle of 85.1 (2)°. In the crystal, a pair of O—H⋯O hydrogen bonds between the carb­oxy­lic acid groups of epalerstat mol­ecules form inversion dimers with an R (2) (2)(8) loop. The dimers are linked by pairs of C—H⋯O hydrogen bonds, enclosing R (2) (2)(20) loops, forming chains propagating along the [101] direction. In addition, the acetone mol­ecules are linked to the chain by a C—H⋯O hydrogen bond. Epalerstat acetone monosolvate was found to be isotypic with epalerstat tertra­hydro­furan solvate [Umeda et al. (2017 ▸). Acta Cryst. E73, 941–944].