1-sec-Butyl-3-[hydroxy(1-methyl-1H-indol-3-yl)methylidene]pyrrolidine-2,4-dione

In the title compound, C(18)H(20)N(2)O(3), the dihedral angle between the indole ring system (r.m.s. deviation = 0.018 angstrom) and the hydroxymethylenepyrrolidine-2,4-dione plane (r.m.s. deviation = 0.036 angstrom) is 9.87 (7)degrees. The keto and enol groups are involved in an intramolecular O-H center dot center dot center dot O hydrogen bond. An intramolecular C-H center dot center dot center dot O interaction also occurs. The sec-butyl group is disordered over two orientations corresponding to an approximate 180 degrees 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 center dot center dot center dot O hydrogen bonds.