3,6,9-Trimethyl-3a,5,9a,9b-tetrahydro-3H-azuleno[4,5-b]furan-2,4,7-trione Ferupennin O InChI=1/C15H16O4/c1-6-4-10(17)13-8(3)15(18)19-14(13)12-7(2)5-9(16)11(6)12/h5,8,12-14H,4H2,1-3H3/t8?,12-,13-,14+/m1/s azuleno[4,5-b]furan-2,4,7(3H)-trione, 3a,5,9a,9b-tetrahydro-3,6,9-trimethyl-, (3aS,9aR,9bS)- rel-(3aR,9aS,9bR)-3,6,9-trimethyl-3a,5,9a,9b-tetrahydroazuleno[4,5-b]furan-2,4,7(3H)-trione