呋喃并[3,4-d]嘧啶-5,7-二酮

diethyl 2-phenylpyrazole-3,4-dicarboxylate

5-乙基吡啶-2,3-二羧酸二乙酯

diethyl 3-cyanopyrazolo[1,5-a]pyrimidine-6,7-dicarboxylate

diethyl 2-aminopyrimidine-4,5-dicarboxylate