(1R*,3S*,5S*)-7,7-dichloro-3-methyl-6-oxobicyclo<3.2.0>heptane-3-carboxylic acid

methyl (1R,2S,5R,7S)-2-allyl-2,7-dimethyl-3-oxo-cis-bicyclo<3.3.0>octane-7-carboxylate

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

tert-butyl cyclopent-3-ene-1-carboxylate

tert-butyl 1-methyl-3-cyclopentencarboxylate