The palladium-catalyzed coupling reaction of 6-iodoisoflavone, prepared fro
m 3'-iodoacetophenone derivative, with 2-methyl-3-butyn-2-ol gave the 6-alk
ynylisoflavone derivative, which was hydrogenated to give the 6-alkylhydrox
yisoflavone (luteone hydrate) 2. Dehydration of 2 gave 2',4',5,7-tetrahydro
xy-6-prenylisoflavone (luteone).