Total synthesis of peshawaraquinone through late-stage [3 + 2] cycloaddition or α-ketol rearrangement

Abstract

Two synthetic approaches to peshawaraquinone, an uncommon and complex naphthoquinone meroterpenoid, are described. Key to the success of these synthetic pathways includes HFIP-promoted metal-free allylation to couple lawsone with allylic alcohols, together with an organo-catalyzed [3 + 2] cycloaddition for constructing the bicyclo[3.2.1]octane core structure. A [2 + 2] photocycloaddition/α-ketol rearrangement sequence was also applied as an alternative approach to peshawaraquinone. Further investigation revealed that natural peshawaraquinone is a racemate.