The solution of trimethylhydroquinone (30, 7.5 g, 49.28 mmol), isophytol (12 g, 40.47 mmol), anhydrous zinc chloride (3 g, 22.01 mmol) and 0.4 mL of glacial acetic acid in 60 mL of absolute ether was refluxed for 1 h. The solvent was then removed in vacuo at 50° C. and the slurry obtained was dissolved in a mixture of 50 mL of petroleum ether and 20 mL of 70% aqueous methanol. The emulsion formed was destroyed by the addition of 20 mL of ether. The ether layer was dried (Na2SO4) and evaporated in vacuo to give a red solid paste that was triturated vigorously with 70 mL of petroleum ether. After cooling to −78° C., the suspension was centrifuged and the supernatant petroleum ether was decanted. Cold petroleum ether (10 mL) was added to the crystalline mass, and the operation was twice repeated to give 10 g (47%) of sticky white solid, which was used in the next step without further purification.
