(1S,2R,4S,6R,8S,9S)-8,9-epoxy-1,4-dimethyl-11-methylene-10-oxotricyclo<6.3.0.02,6>undecane-4-carboxylic acid

methyl (2S,3aR,6aS)-1,2,3,3a,4,5,6,6a-octahydro-2-methyl-4-oxopentalene-2-carboxylate

methyl (2S,3aR,3bS,7aS)-2,3,3a,3b,4,5,7,7a-octahydro-2,3b-dimethyl-5-oxo-1H-cyclopentapentalene-2-carboxylate