2-(3,4-dimethoxy-1-oxidopyridin-2-ylidene)-3,4-dimethoxypyridin-1-ium 1-oxide

8-甲氧基-4-氧代-1,4-二氢-1,5-萘啶-3-羧酸乙酯

5-methyl-4,8-dioxo-1,4,5,8-tetrahydro-[1,5]naphthyridine-3-carboxylic acid ethyl ester

3-hydroxy-2-(3-hydroxy-4-oxo-1H-pyridin-2-yl)-1H-pyridin-4-one