Pterodontic acid

In the title compound, C15H22O2, the C=C bond lengths in the cyclohexene ring and the allylic acid group [1.325 (3) and 1.324 (3) Å] are almost equal and are shorter than those observed in ethylene. The C=O and C—O bond lengths in the allylic acid group [1.201 (3) and 1.321 (3) Å] are almost equal to those of formic acid. There is an intramolecular hydrogen bond between the allylic acid H atom and the hydroxy O atom [C...O = 2.673 (2) Å and C—H...O = 101°].