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

(1S,3S,5R)-6-Chloro-3,6-dimethyl-7-oxo-bicyclo[3.2.0]heptane-3-carboxylic acid

(2S,3aR,6aR)-4-Chloro-2,4-dimethyl-5-oxo-octahydro-pentalene-2-carboxylic acid methyl ester

methyl (2R*,3aS*,3bS*,6aR*,7aR*)-2,3,3a,3b,4,5,6,6a,7,7a-decahydro-2,3b-dimethyl-5-oxo-1H-cyclopentapentalene-2-carboxylate

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