(2S)-3-(1H-Indol-3-yl)-2-(4-methyl-benzene-sulfonamido)-propionic acid monohydrate.

In the title compound, C(18)H(18)N(2)O(4)S·H(2)O, the indole and toluene ring systems are oriented at a dihedral angle of 84.51 (9)°. In the crystal, the components are linked by N-H⋯O, O-H⋯O, C-H⋯O and N-H⋯π inter-actions. These include a short link from the α-C atom of the amino acid fragment.