(4aR,6aS,12aS,12bR,12cS)-15-methyl-4a,5,12,12a,12b,12c-hexahydro-11H-6a,4-(ethanoiminomethano)-1-oxa-10b-azacyclohepta[1,2,3-cd]fluoranthene-6,11(2H)-dione