Concise Enantioselective Total Syntheses of Rearranged <i>ent</i> ‐Trachylobane Diterpenoids (–)‐Wallichanols A and B

Abstract

Abstract Herein, we report the first enantioselective total syntheses of three rearranged ent ‐trachylobane diterpenoids, (–)‐Wallichanol A ( 1 ), (–)‐Wallichanol B ( 2 ), and (–)‐Sanguinolane ( 3 ), using a 13, 17, and 14 step longest‐linear sequences respectively, featuring a novel intramolecular [2 + 2] cycloaddition to construct the unique pentacyclic framework containing an unprecedented tricyclo[3.3.1.0 2,7 ]nonane motif. Other key steps in the synthetic route include a highly challenging, selective alkene reduction via hydrogen atom transfer (HAT), leveraging the thermodynamic preference for a tertiary carbon‐centered radical; a Robinson‐type annulation to construct the tricyclic terpenoid building block; and applying aerobic oxidation at two distinct points to form α ‐hydroxy ketones, facilitating the enantioselective syntheses of these diterpenoids.