With the aid of ᴅʟ-phenylalanine-[2-14C] and ᴅʟ-phenylalanine-[3-14C] it has now been proved that the biogenesis of 7-hydroxy-4′-methoxy-isoflavone (formononetin) in red clover involves a phenyl migration. This is the first phenyl migration to be found in nature.