The product obtained from the condensation of 5-hydroxy-2-methylbenzoic acid with aqueous formaldehyde and hydrochloric acid is dependent on the temperature. If the condensation is carried out at room temperature 3-hydroxy-6-methylphthalide results. This substance can also be obtained by the demethylation of 3-methoxy-6-methylphthalide. If the condensation is carried out at the boiling point the lactone of 8-hydroxymethyl-1,3-benzodioxane-6-methyl-7-carboxylic acid results. Proof of the presence of the m-dioxane and phthalide rings in this latter substance has been established by opening these rings in succession. In both cases this has led by a series of degradative steps to 4-methoxybenzene-1,2,3,5-tetracarboxylic acid. The structure of this acid has been confirmed by its synthesis in six unambiguous steps from mesitylene.
通过5-羟基-2-甲基苯甲酸与水甲醛和盐酸缩合反应所得产物取决于温度。如果在室温下进行缩合反应,则会产生3-羟基-6-甲基邻苯二甲酸内酯。这种物质也可以通过3-甲氧基-6-甲基邻苯二甲酸内酯的去甲基化反应得到。如果在沸点下进行缩合反应,则会产生8-羟甲基-1,3-苯并二氧杂环-6-甲基-7-羧酸内酯。通过依次打开这些环来证明此后一种物质中存在m-二噁烷和邻苯二甲酸内酯环。在这两种情况下,通过一系列降解步骤,最终得到4-甲氧基苯-1,2,3,5-四羧酸。这种酸的结构已通过从甲苯中六步合成得到并得到确认。