3-acetyl-tetrahydropyran-2,4,6-trione

2-acetyl-3-oxo-glutaric acid

2,4-diacetyl-3-oxo-pentanedioic acid anhydride

1,3-丙酮二羧酸二乙酯

diethyl 4-(2-ethoxy-2-oxoethyl)-2,6-dihydroxybenzene-1,3-dicarboxylate