methyl (1R,3S,5R)-3-methyl-6-oxobicyclo<3.2.0>heptane-3-carboxylate

(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