A diastereomer of methyl (1R,3′S)-1′,1′′-dimethyl-2,2′′-dioxo-2H-dispiro­[ace­naphthyl­ene-1,2′-pyrrolidine-3′,3′′-indoline]-4′-carboxyl­ate

In the title compound, C₂₆H₂₂N₂O₄, the central pyrrolidine ring adopts a twist conformation and the cyclo­pentane ring of the dihydro­acenapthylene group adopts an envelope conformation with the spiro C atom as the flap. The naphthalene ring system of the dihydro­acenaphthyl­ene group forms dihedral angles of 83.4 (9) and 61.3 (7)°, respectively, with the mean planes of the pyrrolidine and indole rings. The crystal packing is stabilized by inter­molecular C—H...O hydrogen bonds. The title compound is a diastereomer of a previously reported structure.