2-acetyl-4-methylcyclopent-4-ene-1,3-dione

methyl 2-(2-methoxy-4-methyl-5-oxo-2,5-dihydrofuran-2-yl)acetate

ethyl 3-methyl-2,5-dioxocyclopentenecarboxylate

6-ethyl 1-methyl (Z)-2-methyl-4-oxohex-2-enedioate

ethyl 2-methoxy-4-methyl-5-oxo-2,5-dihydrofuran-2-ylacetate