(2Z)-4-[(2-Hy-droxy-phen-yl)carbamo-yl]prop-2-enoic acid.

In the title compound, C(10)H(9)NO(4), the 2-hy-droxy-anilinic and the 4-oxobut-2-enoic acid groups are almost planar, with r.m.s. deviations of 0.0086 and 0.0262 Å, respectively. The dihedral angle between the two groups is 6.65 (1)°. Intra-molecular N-H⋯O, C-H⋯O and O-H⋯O hydrogen bonds form S(5), S(6) and S(7) ring motifs. In the crystal, the mol-ecules are dimerized due to C-H⋯O and O-H⋯O inter-molecular hydrogen bonds, with R(2) (2)(8) ring motifs. The dimers are inter-linked into polymeric chains along [010] with R(4) (3)(13) ring motifs by C-H⋯O, N-H⋯O and O-H⋯O hydrogen bonds.