3-Carboxymethyl-1H-indole-4-carboxylic acid

In the title compound, C11H9NO4, the carboxyl group bonded to the six-membered ring lies close to the plane of the 1H-indole ring system [dihedral angle = 13.13 (9)degrees], whereas the carboxylic acid group linked to the five-membered ring by a methylene bridge is close to perpendicular [78.85 (9)degrees]. In the crystal, O-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonds link the molecules, generating (110) sheets.