Biomimetic Syntheses of (−)-Gochnatiolides A–C and (−)-Ainsliadimer B

We report the first biomimetic syntheses of (−)-gochnatiolides
A–C and (−)-ainsliadimer B based on our proposed biogenetic
pathway. Our synthesis features one-pot cascade transformations including
Saegusa oxidation, intermolecular Diels–Alder cycloaddition,
and radical-mediated allylic oxidation, which allow for the rapid
generation of (−)-gochnatiolides A–C in a collective
manner. We also disclose an unprecedented “copper effect”
on the stereochemical outcome of the radical-mediated allylic oxidation.
Our synthetic endeavors led to the structural reassignment of (−)-gochnatiolide
B. Ultimately, a biomimetic transformation from gochnatiolide B to
ainsliadimer B was achieved through a remarkable direct enone hydration.

本研究首次基于我们提出的生源合成途径，完成了(-)-戈奇诺内酯A-C（(-)-gochnatiolides A–C）与(-)-锦葵二聚体B（(-)-ainsliadimer B）的仿生全合成。本次合成采用一锅法级联反应策略，涵盖三枝氧化（Saegusa oxidation）、分子间狄尔斯-阿尔德环加成（intermolecular Diels–Alder cycloaddition）以及自由基介导的烯丙基氧化，可快速高效地以汇聚式方式构建(-)-戈奇诺内酯A-C。本研究还首次报道了前所未有的"铜效应"对自由基介导烯丙基氧化反应立体化学结果的调控作用。通过本次合成研究，我们对(-)-戈奇诺内酯B（(-)-gochnatiolide B）的结构归属进行了重新修正。最终，通过极具创新性的直接烯酮水合（enone hydration）反应，我们成功实现了从(-)-戈奇诺内酯B到(-)-锦葵二聚体B的仿生转化。