(4S)-3-Methyl-5,6,7,8-tetra-hydro-4H-spiro-[[1,2]oxazolo[5,4-b]quinoline-4,3'-indole]-2',5-dione.

In the title compound, C18H15N3O3, the dihedral angle between the mean planes of the quinoline and indole ring systems [r.m.s. deviations = 0.189 (2) and 0.027 (2) Å, respectively] is 88.65 (5)°. The cyclo-hexene ring of the quinoline ring system adopts an envelope conformation with the central -CH2- C atom as the flap. In the crystal, mol-ecules are linked by two pairs of N-H⋯O hydrogen bonds, forming inversion dimers, and enclosing R 2 (2)(14) ring motifs. This arrangement results in the formation of chains propagating along [100].