Facile Total Syntheses of Putative and Revised Structures of Pethybrene

The structural identity of pethybrene was confirmed as theoretically proposed 6‐5‐5 tricyclic structure through total syntheses of two putative structures. The originally proposed structure 1 was synthesized in 13 steps via Intramolecular Pauson‐Khand reaction to form the triquinane skeleton and the newly proposed structure from a theoretical study 2 was obtained from a known [2+2] cycloaddition product in 3 steps. Facile synthesis of the putative structure of pethybrene via Pauson‐Khand reaction and newly proposed structure via [2+2] cycloaddition reaction has been achieved. The total synthesis confirmed that the newly proposed structure matches with the natural product, pethybrene.