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

A total synthesis of the caribenol A (1), 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 (1) and a biomimetic oxidation reaction for the formation of the 2-hydroxyfuran-2­(5H)-one motif of caribenol A (1) as key steps. This synthetic approach also reveals that the sp2 carbon at C(2) in substrate 8 is a critical factor for the formation of the tricyclic [5–7–6] skeleton in 7.本研究完成了新型天然产物卡拉宾醇A（1）的全合成，该化合物具有引人关注的四环骨架。该合成路线以分子内狄尔斯-阿尔德（intramolecular Diels–Alder, IMDA）反应为关键步骤，高效构建了卡拉宾醇A（1）的三环[5-7-6]骨架；并通过仿生氧化反应构建了其2-羟基呋喃-2(5H)-酮结构单元。该合成策略同时揭示：底物8中C(2)位的sp²杂化碳原子，是生成7中三环[5-7-6]骨架的关键影响因素。