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The title compound, epalrestat {systematic name: (5Z)-5-[(2E)-2-methyl-3-phenylprop-2-en-1-yl-idene]-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 R2²(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(tetrahydrofuran) hydrogen bond. A combination of thermal analysisand 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). [ABSTRACT FROM AUTHOR]

The title compound, C12H16O4 (systematic name: 2,4-dihy­droxy-6-pentyl­benzoic acid) is a natural product isolated from C. sanguinea (Schaer.) and is reported to have various pharmacological activities. The mol­ecule is approximately planar (r.m.s. deviation for the non-H atoms = 0.096 Å) and features an intra­molecular O—H⋯O hydrogen bond. In the crystal, each olivetolic acid mol­ecule is connected to three neighbours via O—H⋯O hydrogen bonds, generating (10-1) sheets. This crystal is essentially isostructural with a related resorcinolic acid with a longer alkyl chain. [ABSTRACT FROM AUTHOR]