The structure of the title compound, C17H20O4 [systematic name: (1aS,3aR,-4aS,5aR)-15-(acetoxy)linden-7(11),8-trieno-12,8-lactone or (4aR,5S,5aR,6aS,-6bR)-5-(acetoxymethyl)-4a,5,5a,6,6a,6b-hexahydro-3,6b-dimethylcyclopropa[2,3]-indeno[5,6-b]furan-2(4H)-one, ent-chloranthalactone C], a natural product isolated from the whole plant Chloranthus japonicus Sieb., is a typical lindenane-type sesquiterpenoid. The molecule comprises a bicyclo[3.1.0]hexane ring (A/B system) bearing an acetoxymethyl (C-4) group, a bicyclo[4.3.0]nonane ring (B/C system) containing a double bond (C-8/9) and a chiral quaternary carbon (C-10), and a 7(11)-en-12,8-olide structural moiety on the cyclohexan-8-ene (C ring). In the tetracyclic skeleton, the 1,3-cyclopropane ring has a β-configuration, and atoms H-5 and H3-14 have α- and β-orientations, respectively. In the crystal, the molecules are assembled into a two-dimensional network by weak O...H/H...O interactions. Hirshfeld surface analysis illustrates that the greatest contributions are from H...H (55.2%), O...H/H...O (34.6%) and C...H/H...C (8.9%) contacts. [ABSTRACT FROM AUTHOR]