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Treatment of 2,5-dimethyl-2-5-hexanediol (I) with dry hydrogen chloride in EtOH gives rise to the dichloro compound (II). Subsequent Friedel-Crafts condensation of dichloride (II) with toluene (III) in the presence of AlCl3 affords the tetrahydronaphthalene derivative (IV) (1). This is then condensed with mono-methyl terephthalic acid chloride (V) to produce ketone (VI). Wittig reaction of (VI) with methylene triphenylphosphorane leads to olefin (VII). Finally, alkaline hydrolysis of the methyl ester group of (VII) furnishes the target carboxylic acid

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The intermediate tetrahydronaththalene (VI) has been prepared by an alternative procedure. Friedel-Crafts condensation of dihydro-2,2,5,5-tetramethyl-3(2H)-furanone (I) with toluene (II) by means of AlCl3 produces tetrahydronaphthalenone (III). This is reduced to alcohol (IV) employing NaBH4 in MeOH. Subsequent dehydration of (IV) with POCl3 in pyridine leads to the dihydronaphthalene (V). Then, catalytic hydrogenation of (V) over Pd/C provides the key pentamethyltetrahydronaphthalene (VI)

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In a different strategy, electrophilic bromination of tetrahydronaphthalene (I) with Br2 and AlCl3 produces aryl bromide (II). Metalation of (II) with butyllithium, followed by reaction with triisopropyl borate, gives rise to the boronic acid (III). Treatment of methyl 4-acetylbenzoate (IV) with trifluoromethanesulfonic anhydride leads to the vinyl triflate (V). Then, Suzuki coupling of boronic acid (III) with vinyl triflate (V) furnishes the gem-diarylethylene derivative (VI). Finally, basic hydrolysis of the methyl ester group of (VI) provides the title carboxylic acid