4,7-bis(ethoxycarbonyl)-6,8-dimethyl-1(2H)-phthalazinone

7-ethoxycarbonyl-6,8-dimethyl-isochroman-1,4-dione

6-ethoxycarbonyl-5,7-dimethyl-3-hydroxy-3-methylphthalide

4-ethoxycarbonyl-3,5-dimethylphthalic acid

3,5-dimethyl-4-ethoxycarbonyl-phthalic anhydride