4-(3-oxo-1,2-dihydroinden-2-yl)butanoic acid

methyl 1-(2-acetyloxyethyl)-2-oxocyclopentane-1-carboxylate

乙基5-氧代-1-环戊烯-1-羧酸酯

2-cyclohexylcyclopentan-1-one

ethyl 9-(5-oxocyclopenten-1-yl)nonanoate