Synthesis of the [6.6.7.5] Tetracyclic Core of Calyciphylline N via a Boc-Mediated Oxidative Dearomatization/Diels–Alder Approach

A sequential process involving Boc-mediated oxidative dearomatization and inter/intramolecular Diels-Alder reaction was investigated. Based on an intermolecular Diels-Alder reaction and subsequently a radical 7-endo-trig type cyclization, the [6.6.7.5] tetracyclic core of Calyciphylline N was assembled.