In the crystal structure of the title compound, C(11)H(15)NO(4)S, two independent mol-ecules are present per asymmetric unit; they are dimerized through O-H⋯O hydrogen bonds between their carb-oxy groups to generate R(2) (2)(8) loops. An intra-molecular N-H⋯O link in one of the mol-ecules closes an S(5) ring. The dimers are linked by N-H⋯O and C-H⋯O hydrogen bonds to form a three-dimensional network. The C atoms of the isopropyl group of one of the mol-ecules are disordered over two orientations in a 3:1 ratio.