In the structure of the title compound, C(27)H(39)N(3)O(3), each of the (4-oxopiperidin-1-yl)methyl residues adopts a flattened chair conformation (with the N and carbonyl groups being oriented to either side of the central C(4) plane) and they occupy positions approximately orthogonal to the central benzene ring [C(benzene)-C-C(methyl-ene)-N torsion angles 103.4 (2), -104.4 (3) and 71.9 (3)°]; further, two of these residues are oriented to one side of the central benzene ring with the third to the other side. In the crystal packing, supra-molecular layers in the ab plane are sustained by C-H⋯O inter-actions.