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 (2aR,2bR,4S,5aS,6aS)-decahydro-2,2-dichloro-2a,4-dimethyl-1-oxocyclobutapentalene-4-carboxylate

(2R,3aS,3bS,6aR,7aR)-4,4-Dichloro-2,3b-dimethyl-5-oxo-decahydro-cyclopenta[a]pentalene-2-carboxylic acid methyl ester