3,3',4,4'-Tetramethoxy-2,2'-bipyridine

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

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