Yang Baochao, Lin Kuaikuai, Shi Yingbo, Gao Shuanhu
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663N Zhongshan Road, Shanghai, 200062, China.
Nat Commun. 2017 Sep 20;8(1):622. doi: 10.1038/s41467-017-00440-8.
Stereoselective construction of polycyclic rings with all-carbon quaternary centers, and vicinal all-carbon quaternary stereocenters, remains a significant challenge in organic synthesis. These structures can be found in a wide range of polycyclic natural products and drug molecules. Here we report a Ti(Oi-Pr)-promoted photoenolization/Diels-Alder (PEDA) reaction to construct hydroanthracenol and related polycyclic rings bearing all-carbon quaternary centers. This photolysis proceeds under mild conditions and generates a variety of photo-cycloaddition products in good reaction efficiency and stereoselectivity (48 examples), and has been successfully used in the construction of core skeleton of oncocalyxones, tetracycline and pleurotin. It also provides a reliable method for the late-stage modification of natural products bearing enone groups, such as steroids. The total synthesis of oncocalyxone B was successfully achieved using this PEDA approach.Anthracenols with multiple chiral centres are common motifs in natural products. Here, the authors show a highly stereoselective photoenolization/Diels-Alder methodology involving a key Lewis acid reagent enabling the efficient construction of a family of anthracenol derivatives with quaternary centers.
具有全碳季碳中心以及相邻全碳季碳立体中心的多环的立体选择性构建，在有机合成中仍然是一项重大挑战。这些结构存在于多种多环天然产物和药物分子中。在此，我们报道了一种由异丙醇钛促进的光烯醇化/狄尔斯-阿尔德（PEDA）反应，用于构建氢化蒽醇以及带有全碳季碳中心的相关多环。这种光解反应在温和条件下进行，能以良好的反应效率和立体选择性生成多种光环加成产物（48个实例），并且已成功用于构建癌萼酮、四环素和侧耳素的核心骨架。它还为带有烯酮基团的天然产物（如甾体）的后期修饰提供了一种可靠方法。利用这种PEDA方法成功实现了癌萼酮B的全合成。具有多个手性中心的蒽醇是天然产物中的常见结构单元。在此，作者展示了一种高度立体选择性的光烯醇化/狄尔斯-阿尔德方法，该方法涉及一种关键的路易斯酸试剂，能够高效构建一系列具有季碳中心的蒽醇衍生物。
