A triclinic polymorph of methyl (3R,3′S)-1′,1′′-dimethyl-2,2′′-dioxodispiro­[indoline-3,2′-pyrrolidine-3′,3′′-indoline]-4′-carboxyl­ate

In the title compound, C(22)H(21)N(3)O(4), the central pyrrolidine ring adopts a C-envelope conformation with a C atom 0.6593 (13) Å displaced from the mean plane formed by the remaining ring atoms. The indoline ring systems (r.m.s. devisations of 0.0356 and 0.0547 Å) are almost perpendicular to the mean plane of the pyrrolidine ring, making dihedral angles of 89.7 (6) and 82.5 (6)°. The acetate group attached to the pyrrolidine ring assumes an extended conformation. In the crystal,N—H⋯O and C—H⋯O hydrogen bonds connect adjacent molecules, forming an infinite tape extending along [1-1-1]. The crystal packing is further consolidated by strong π–π inter­actions with a centroid–centroid distance of 3.2585 (8) Å. The title compound is a polymorph of previously reported monoclinic structure [Ganesh et al. (2012 ▶). Acta Cryst. E68, o2902–o2903].