5-methoxy-4-oxopyran-2-carboxylic acid

2-(羟基甲基)-5-甲氧基-4H-吡喃-4-酮

3-甲氧基-2-甲基-4H-吡喃-4-酮

5,6-dimethoxy-4-oxo-4H-pyran-2-carboxylic acid methyl ester