2′, 4′, 5, 7-Tetrahydroxyisoflavone was partially benzoylated with benzoyl chloride to give 7-benzoyloxy-2′, 4′, 5-trihydroxyisoflavone. The condensation of the 7-(benzoyloxy) isoflavone with 2-methyl-3-buten-2-ol, followed by the hydrolysis of the resultant 3′-(3- methyl-2-butenyl) isoflavone gave licoisoflavone A. Its 5′-(3-methyl-2-butenyl) isomer was also synthesized from 5-benzoyloxy-2′, 4′, 7-trihydroxyisoflavone in a similar manner.
