Extending pummerer reaction chemistry. Application to the total synthesis of (+/-)-dibromoagelaspongin

The sponge metabolite dibromoagelaspongin was synthesized in 16 steps from imidazole. The route features two successive oxidative cyclizations with complete control of regiochemistry to deliver the unusual triaminomethane core of the target. These oxidative cyclizations likely resulted from Pummerer-like processes on the imidazole-2-sulfoxide (sulfide) precursors.