1H-cyclopenta[a]pentalene-1,5(2H)-dione, 3,3a,3b,4-tetrahydro-2,2,3b-trimethyl-4-methylene-, (3aS,3bS)- InChI=1/C15H16O2/c1-8-12(16)6-9-5-10-11(15(8,9)4)7-14(2,3)13(10)17/h5-6,11H,1,7H2,2-4H3/t11-,15-/m1/s rel-(3aR,3bR)-2,2,3b-trimethyl-4-methylene-3,3a,3b,4-tetrahydro-1H-cyclopenta[a]pentalene-1,5(2H)-dione