Total Synthesis of Termicalcicolanone A via Organocatalysis and Regioselective Claisen Rearrangement

A total synthesisof an anticancer xanthonenatural product termicalcicolanone A utilizing multiple nucleophilic aromatic substitutionsand pericyclic reactionshas been developed. The pyrano[3,2-b] xanthen-6-one scaffold was constructed via NHC-catalyzed aroylation to produce the benzophenoneintermediate, Claisen cyclization to form the pyranring, and intramolecular 1,4-addition to construct the xanthoneframework. The prenylgroup was introduced in the final stages of the synthesis through regioselective Claisen rearrangement. The synthesis has been achieved in 19 steps.