The title compound, C24H29NO4, is the product of a Petrenko-Kritchenko condensation of 1,5-bis(2-formylphenoxy)-3-oxapentane, pentan-3-one and methylammonium acetate in ethanol. The molecule has mirror symmetry. The aza-14-crown-3 ether ring adopts a bowl conformation stabilized by a weak intramolecular C - H⋯O hydrogen bond. The conformation of the C - O - C - C - O - C - C - O - C polyether chain is t-g+-t-t-g--t (t = trans, 180°; g = gauche, ±60°). The dihedral angle between the benzene rings fused to the aza-14-crown-4-ether moiety is 72.68(4)°. The piperidinone ring adopts a chair conformation. The nitrogen atom has a trigonal-pyramidal geometry, the sum of the bond angles being 335.9°. In the crystal, the molecules are linked by weak C - H⋯O interactions, forming zigzag chains propagating along the  direction.
Nguyen, V. T., Truong, H. H., Le, T. A., Soldatenkov, A. T., Thi, T. A. D., Tran, T. T. V., … Khrustalev, V. N. (2017). Crystal structure of 22,24,25-trimethyl-8,11,14-trioxa-25-azatetracyclo[19.3.1.02,7.015,20]pentacosa-2,4,6,15(20),16,18-hexaen-23-one. Acta Crystallographica Section E: Crystallographic Communications, 73, 118–121. https://doi.org/10.1107/S2056989016020508