A method for preparing a precursor of α-CEHC, 2,5,7.8-tetramethyl-2-(2′-carboxyethyl) -6-acetoxychroman, which comprises the following steps:
- a) carrying out an acid-catalyzed reaction of condensation of trimethyl hydroquinone with linalool in boiling n-octane;
- b) treating the product obtained in step a) in said condensation reaction with acetic anhydride in pyridine;
- c) ozonizing the product from step b) in the presence of Ba(OH)2 in acetone at room temperature;
- d) oxidizing the product from step c) in the same solvent with Jones' reagent (CrO3/H2SO4);
- e) isolating the target product by column chromatography.