1-sec-Butyl-3-[hy-droxy(1-methyl-1H-indol-3-yl)methyl-idene]pyrrolidine-2,4-dione.

In the title compound, C18H20N2O3, the dihedral angle between the indole ring system (r.m.s. deviation = 0.018 A) and the hy­droxy­methyl­enepyrrolidine-2,4-dione plane (r.m.s. deviation = 0.036 A) is 9.87 (7)°. The keto and enol groups are involved in an intra­molecular O—H⋯O hydrogen bond. An intra­molecular C—H⋯O inter­action also occurs. The sec-butyl group is disordered over two orientations corresponding to an approximate 180° rotation about the N—C bond, with occupancies of 0.670 (6) and 0.330 (6). In the crystal, mol­ecules are linked into chains along the c axis by C—H⋯O hydrogen bonds.