Abstract
There are two molecules in the asymmetric unit of the title compound, C15H11NO4S. The heterocyclic thiazine rings in both molecules adopt half-chair conformations with the S and N atoms displaced by 0.455 (4) and 0.254 (4) angstrom, respectively, in one molecule, and 0.480 (4) and 0.224 (5) angstrom in the other, on opposite sides of the mean planes formed by the remaining ring atoms. The crystal structure is stabilized by intermolecular N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds. In addition, intramolecular O-H center dot center dot center dot O interactions are also present.