3,4,3',4'-tetramethyl-[1,1']bipyrrolyl-2,5,2',5'-tetraone

1-amino-3,4-dimethylpyrrole-2,5-dione

6,7-dimethylindolizine-5,8-dione

2,3-二甲基丁二酸

2-hydroxy-3,4-dimethyl-2H-furan-5-one