The radical alkylation of 2,3-dimethoxy-5-methylbenzoquinone (I) with bis(11-acetoxyundecanoyl)peroxide (II) at 85-90 C gives 2,3-dimethoxy-5-methyl-6-(10-acetoxydecyl)benzoquinone (III), which is hydrolyzed with concentrated HCl in methanol.
The Friedel-Kraft condensation of 3,4,5-trimethoxytoluene (I) with ethyl 9-chloroformylnonanoate (II) by means of AlCl3 in nitrobenzene gives 9-(2-hydroxy-3,4-dimethoxy-6-methylbenzoyl)nonanoic acid (III), which is reduced with Zn in refluxing aqueous HCl yielding 10-(2-hydroxy-3,4-dimethoxy-6-methylphenyl)decanoic acid (IV). The oxidation of (IV) with potassium nitrosodisulfonate in water-acetone affords 2,3-dimethoxy-5-methyl-6-(9-carboxynonyl)benzoquinone (V), which is esterified with ethanol HCl to the corresponding ethyl ester (VI). Finally, this compound is reduced with LiAlH4 in ether.