Asymmetric Total Synthesis of (+)‐Ineleganolide

Polycyclic cembrane diterpenoids and norditerpenoids have garnered sustained interest from the synthetic community due to their unique polycyclic frameworks and promising biological activities. Herein, we report a 13‐step total synthesis of (+)‐ineleganolide, a highly oxidized cembrane norditerpenoid possessing a synthetically challenging [6,7,5,5,5] cage‐type pentacyclic scaffold. This synthesis is highlighted by a novel strategy relying on an intramolecular Diels–Alder reaction that stereoselectively constructs the pivotal [6,6,5,5,5] pentacyclic framework as a single diastereoisomer, addressing stereochemical control challenges. In the late‐stage elaboration, a tandem epoxidation/Meinwald rearrangement efficiently forges the sterically congested central seven‐membered ring. This synthetic strategy provides a new blueprint for accessing other members of the cembrane norditerpenoid family.