3,6,9-Trimethyl-2,3-dihydro­benzo[de]chromene-7,8-dione

The title sesquiterpene ortho-naphthoquinone compound, C15H14O3, was isolated from Thespesia populnea. There are four independent mol­ecules (A, B, C and D) in the asymmetric unit. The conformations of mol­ecules A and B differ from those observed for C and D. In all four mol­ecules, the pyran ring adopts an envelope conformation, with the methyl­ene C atom as the flap atom. The mol­ecules are arranged in layers parallel to the (100) plane, and are inter­connected into a three-dimensional network by C—H⋯O inter­actions.