diethyl 1,2,5-oxadiazole-3,4-dicarboxylate 2-oxide

1,3,4,6,7,8,9,9a-octahydroquinolizin-2-one

香豆素-4-乙酸

4,6-二羟基吡嗪-3-羧酸乙酯

diethyl 2-ethyl-3-oxopentanedioate