π(4)s + π(2)s Cycloaddition of Spiroepoxycyclohexa-2,4-dienone, Radical Cyclization, and Oxidation-Aldol-Oxidation Cascade: Synthesis of BCDE Ring of Atropurpuran

Synthesis of a tetracyclic ring system (BCDE) of atropurpuran is described. Oxidative dearomatization, cycloaddition of spiroepoxycyclohexa-2,4-dienone, radical cyclization, and a tandem oxidation–aldol–oxidation are the key features of our methodology.