methyl (2aR,2bR,2cR,4S,5aR,5bS,5cS)-decahydro-4,5b-dimethyl-2-oxo-1H-cyclopenta[a]cyclopropa[cd]pentalene-4-carboxylate

(3aS,5S,6aR)-5-Methyl-1-oxo-octahydro-pentalene-2,5-dicarboxylic acid 2-ethyl ester 5-methyl ester

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

methyl (1R,2aR,2bR,2cR,4S,5aR,5bS,5cS)-1-(benzoyloxy)-decahydro-4,5b-dimethyl-2-oxo-1H-cyclopenta[a]cyclopropa[cd]pentalene-4-carboxylate