Showing structure for 16-(3,3-dimethyloxirane-2-carbonyl)-11,11,15-trimethyl-6,10,19-trioxapentacyclo[13.3.1.0²,⁷.0⁹,¹⁸.0¹²,¹⁷]nonadeca-1,3,7,9(18)-tetraen-5-one