戊二酸

2-ethoxy-6-hydroxy-pyridine-3,5-dicarboxylic acid

2H-吡喃-2,6(3H)-二酮

5-methoxycarbonyl-pyrazoline-3-carboxylic acid methyl ester

2,4-bis-(bis-ethoxycarbonyl-methyl)-cyclobutane-1,1,3,3-tetracarboxylic acid tetraethyl ester