In the title compound, C(7)H(11)NO(4), prepared via a Morita-Baylis-Hillman adduct, the five-membered ring bearing three O atoms approximates to a twisted conformation, whereas the other ring is close to an envelope, with a C atom in the flap position. The dihedral angle between their mean planes (all atoms) is 23.11 (9)°. The new stereocenters are created in a trans-diaxial configuration. In the crystal, O-H⋯O and O-H⋯(O,O) hydrogen bonds link the mol-ecules, generating a three-dimensional network. A weak C-H⋯O inter-action also occurs.