Total Synthesis of Icaritin via Microwave-assistance Claisen Rearrangement

The novel total synthesis of icaritin (1), naturally occurring with important bioactive 8-prenylflavonoid, was performed via a reaction sequence of 8 steps including Baker-Venkataraman reaction, chemoselective benzyl or methoxymethyl protection, dimethyldioxirane (DMDO) oxidation, O-prenylation, Claisen rearrangement and deprotection, starting from 2,4,6-trihydroxyacetophenone and 4-hydroxybenzoic acid in overall yields of 23%. The key step was Claisen rearrangement under microwave irradiation. MS, 1H and 13C NMR techniques have been used to confirm the structures of all synthetic compounds.