合成路线1

The condensation of diethyl malonate (XV) with 3-methylpent-3-en-2-one (XVI) by means of sodium ethoxide in ethanol gives 5,6-dimethyl-4-ethoxycarbonylcyclohexane-1,3-dione (XVII), which is aromatized to 5,6-dimethyl-4-ethoxycarbonylresorcinol (XIX) by treatment with FeCl3 in refluxing acetic acid, or by bromination to 2-bromo-5,6-dimethyl-4-ethoxycarbonylresorcinol and debromination with H2 over Pd/C. The methylation of (XIX) with diazomethane or methyl iodide and K2CO3 gives the corresponding dimethyl ether (XX), which is hydrolyzed with NaOH affording 2,4-dimethoxy-5,6-dimethylbenzoic acid (XXI). This acid by reaction with SOCl2 gives the acyl chloride (XXII), which by reaction with NH3 is converted into the amide (XXIII). The reaction of (XXIII) with tert-butyl hypochlorite affords the N-chloroamide (XXIV), which is photolyzed to the intermediate iminolactone (XXV) and immediately hydrolyzed to 4-methyl-5,7-dimethoxyphthalide (XXVI).