ethyl 1-oxopyrano[3,4-c]pyridine-3-carboxylate

ethyl 3-(benzenesulfonyl)-2-oxopropanoate

ethyl 3-(4-methylphenyl)sulfonyl-2-oxopropanoate

ethyl 4,5-dioxopyrrolidine-3-carboxylate

5-苯基吡唑-3-羧酸乙酯