(2R*,3aS*,3bR*,7aR*)-2,3,3a,3b,4,5,7,7a-octahydro-2,3b-dimethyl-5-oxo-1H-cyclopentapentalene-2-carboxylic acid

methyl (2R*,3aS*,6aR*)-2,4-dimethyl-1,2,3,3a,6,6a-hexahydropentalene-2-carboxylate

(1R*,3S*,5R*,6S*)-1-methyl-9-oxatricyclo<3.2.2.03,6>nonan-8-one