2,5-Dimethyl-3,4-furandicarboxylic acid

diethyl 2,3-diacetylbut-2-enedioate

3-Hydroxy-3-methyl-5-oxo-cyclopent-1-ene-1,2-dicarboxylic acid diethyl ester

1,1-(1,4-亚苯基)二(2,5-二甲基-1H-吡咯-3,4-二羧酸)四乙酯