Crystal structure and Hirshfeld surface analysis of dimethyl (1R*,3aS*,3a(1) R*,6aS*,9R*,9aS*)-3a(1),5,6,9a-tetra-hydro-1H,4H,9H-1,3a:6a,9-di-epoxy-phenalene-2,3-di-carboxyl-ate.

The title di-epoxy-phenalene derivative, C(17)H(18)O(6), comprises a fused cyclic system containing four five-membered rings (two di-hydro-furan and two tetra-hydro-furan) and one six-membered ring (cyclo-hexa-ne). The five-membered di-hydro-furan and tetra-hydro-furan rings adopt envelope conformations, and the six-membered cyclo-hexane ring adopts a distorted chair conformation. Two methyl carboxyl-ate groups occupy adjacent positions (2- and 3-) on a tetra-hydro-furan ring. In the crystal, two pairs of C-H⋯O hydrogen bonds link the mol-ecules to form inversion dimers, enclosing two R (2) (2)(6) ring motifs, that stack along the a-axis direction and are arranged in layers parallel to the bc plane.