In the title compound, C(11)H(11)NO(3), the dihedral angle between the benzene ring and the cyclo-propane ring is 63.2 (1)°. In the crystal, mol-ecules are linked through classical cyclic carb-oxy-lic acid O-H⋯O hydrogen-bond inter-actions [graph set R(2) (2)(8)] giving centrosymmetric dimers which are extended along the b-axis direction through amide N-H⋯O hydrogen-bond inter-actions, giving o...

IN THE ZWITTERIONIC TITLE COMPOUND (SYSTEMATIC NAME: 4-{[amino(inimio)methyl]amino}benzenesulfonate), C(7)H(9)N(3)O(3)S, the dihedral angle between the plane of the guanidine grouping and the benzene ring system is 44.87 (7)°. The crystal packing is stabilized by inter-molecular N-H⋯O hydrogen bonds involving all the potential donors.

The crystal structure of the title compound, C5H4N2O2, is built of acid mol-ecules located on a mirror plane. They form sheets stacked along the b-axis direction. The mol-ecules inter-act via O-H⋯N hydrogen bonds, forming [001] chains, and weak van der Waals inter-actions.