Synthesis of (+/-)-clusianone: High-yielding bridgehead and diketone substitutions by regioselective lithiation of enol ether derivatives of bicyclo[3.3.1]nonane-2,4,9-triones

[GRAPHICS] A concise synthesis of the polyprenylated acylphloroglucinol natural product, clusianone, in racemic form, is described. An Effenburger cyclization generated a core bicyclo[3.3.1] nonane-trione structure, which was then elaborated by means of regioselective lithiation reactions.