Crystal structure of (5′S,8′S)-3-(2,5-di-methylphenyl)-8-methoxy-3-nitro-1-aza-spiro[4.5]decane-2,4-dione

The title compound, C₁₈H₂₂N₂O₅, was synthesized by nitrification of its enol precursor. The pyrrolidine ring plane adopts a twisted conformation about the C - C bond linking the spiro centre and the C=O group remote from the N atom. It makes dihedral angles of 71.69 (9) and 88.92 (9)°, respectively, with the benzene ring plane and the plane defined by the four C atoms that form the seat of the of the cyclohexane chair. At the spiro centre, the NH group is axial and the C=O group is equatorial with respect to the cyclohexane ring. In the crystal, inversion dimers linked by pairs of N - H⋯O hydrogen bonds generate R2(8) loops. The dimers are linked by C - H⋯O interactions, generating a three-dimensional network.