Asymmetric Total Synthesis of Caribenol A via an Intramolecular Diels–Alder Reaction

A total synthesis of the caribenol A (<b>1</b>), a novel natural product with an intriguing tetracyclic framework, has been achieved. The synthesis features an intramolecular Diels–Alder (IMDA) reaction for the facile construction of the tricyclic [5–7–6] skeleton of caribenol A (<b>1</b>) and a biomimetic oxidation reaction for the formation of the 2-hydroxyfuran-2­(5<i>H</i>)-one motif of caribenol A (<b>1</b>) as key steps. This synthetic approach also reveals that the sp² carbon at C(2) in substrate <b>8</b> is a critical factor for the formation of the tricyclic [5–7–6] skeleton in <b>7