(4S)-3-Methyl-5,6,7,8-tetrahydro-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 cyclohexene ring of the quinoline ring system adopts an envelope conformation with the central –CH2– C atom as the flap. In the crystal, molecules 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].