Futoenone, a neolignan from Magnolia soulangiana

In the title compound, (2R,4R,5S,5aR)-rel-(−)-4-(1,3-benzodioxol-5-yl)-2,3,4,5-tetra­hydro-7-methoxy-5-methyl-8H-2,5a-methano-benzoepin-8-one, C20H20O5, the tetra­hydro­furan ring has an envelope conformation, and the semi­quinone ring is somewhat non-planar, with deviations from coplanarity of up to 0.1603 (13) A.