(-)-(3a'S,4'S,9b'S,1R,2S,5R)-4'-Ethyl-3a',4',5',7',8',9b'-hexahydro-2-isopropyl-5-methyl-2'-phenyl­spiro­[cyclo­hexane-1,7'-dioxino[3,2-e]isoindole]-1',3',9'-trione

The title compound, C₂₇H₃₃NO₅, obtained from diethyl ether, crystallizes in space group P2₁ with four molecules in the asymmetric unit. The dioxinone and imide rings are almost planar, whereas the cyclo­hexane and cyclohexene rings form distorted conformations. The crystal structure confirms an earlier proposal about the stereoselectivity of Diels-Alder reactions to spiro­cyclic chiral 1,3-dienes.