Absolute configuration of isoeichlerialactone

The title seco-dammarane triterpenoid, C(27)H(42)O(4) (systematic name: 3-{(3S,3aR,5aR,6S,7S,9aR,9bR)-6,9a,9b-trimethyl-3-[(R)-2-methyl-5-oxotetra­hydro­furan-2-yl]-7-(prop-1-en-2-yl)dodeca­hydro-1H-cyclo­penta­[a]naphthalen-6-yl}propanoic acid), has been isolated for the first time from the seeds of Aglaia forbesii. The mol­ecule has three fused rings and all rings are in trans-fused. The two cyclo­hexane rings are in standard chair conformations and the cyclo­pentane ring adopts an envelope conformation. Its absolute configuration was determined by the refinement of the Flack parameter to 0.26 (17). In the crystal, mol­ecules are linked into chains along [010] by O—H⋯O hydrogen bonds.