The palladium-catalyzed coupling reaction of 6-iodoisoflavone, prepared from 3'-iodoacetophenone derivative, with 2-methyl-3-butyn-2-ol gave the 6-alkynylisoflavone derivative, which was hydrogenated to give the 6-alkylhydroxyisoflavone (luteone hydrate) 2. Dehydration of 2 gave 2',4',5,7-tetrahydroxy-6-prenylisoflavone (luteone).