Total Syntheses of Highly Oxidized <i>ent</i>-Kaurenoids Pharicin A, Pharicinin B, 7-<i>O</i>-Acetylpseurata C, and Pseurata C: A [5+2] Cascade Approach

Abstract

The unprecedented oxidative dearomatization-induced [5+2] cycloaddition/pinacol-type 1,2-acyl migration cascade efficiently generates a quaternary carbon center and assembles the highly oxygenated bicyclo[3.2.1]octane framework of ent-kaurene diterpenoids. By incorporation of the subsequent retro-aldol/aldol process and singlet oxygen ene reaction, this concise and convergent approach has enabled the first asymmetric total syntheses of pharicin A, pharicinin B, 7-O-acetylpseurata C, and pseurata C.