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

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

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

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

(2S,3aR,3bS,7aS)-4-[1-Hydroxy-meth-(Z)-ylidene]-2,3b-dimethyl-5-oxo-2,3,3a,3b,4,5,7,7a-octahydro-1H-cyclopenta[a]pentalene-2-carboxylic acid