Natural diterpenoid ludongnin, octa­hydro-5′-hydroxy-7a-methyl-8′-methyl­ene­spiro­[isobenzo­furan-4(1H),4′(3′H)-[1H-7,9a]­methano­cyclo­hepta­[c]­pyran]-1′,3,9′(3aH,4′aH)-trione

The asymmetric unit of ludongnin consists of two mol­ecules of C₂₀H₂₄O₆. The hydroxyl group of each mol­ecule participates in a hydrogen bond with the carbonyl oxy­gen of the δ-lactone moiety of a translationally related mol­ecule, thus giving rise to the two symmetry-independent sets of infinite chains in the crystal, one of which is stretched along the c and another along the a axis of the crystal.