3a,5,5,8-Tetramethyl-5a,6,7,8-tetrahydro-5H-cyclopenta[c]pentalene-3,4-dione InChI=1/C15H20O2/c1-9-5-6-10-13(2,3)12(17)14(4)11(16)7-8-15(9,10)14/h7-10H,5-6H2,1-4H3/t9-,10?,14+,15?/m1/s Silphinen-3,5-dione cyclopenta[c]pentalene-3,4(3aH,5H)-dione, 5a,6,7,8-tetrahydro-3a,5,5,8-tetramethyl-, (3aS,8R)- rel-(3aR,8S)-3a,5,5,8-tetramethyl-5a,6,7,8-tetrahydrocyclopenta[c]pentalene-3,4(3aH,5H)-dione