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

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

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

tert-butyl 1-methyl-3-cyclopentencarboxylate

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