Attempt was made for direct determination of the absolute configuration of methyl group at C-4 and C-10 in guaiol (I) by degradation of an α, β-unsaturated ketone (IX) derived from dihydroxyguaiol (II). Since S-(+)-2-methylglutaric acid (XIII) and 4-hydroxyvaleric γ-lactone (XIV) were obtained, the C-4 methyl group in guaiol possesses the α-configuration and guaiol should be represented by (XV).
