Detailed herein are our synthetic studies toward the preparation of the C₁₈- and C₁₉-benzenoid cephalotane-type norditerpenoids. Guided by chemical network analysis, the core structure of this natural product family was constructed in a concise manner using an iterative cross-coupling, followed by a formal inverse-electron-demand [4 + 2] cycloaddition. Initial efforts to functionalize an alkene group in the [4 + 2] cycloadduct using a Mukaiyama hydration and a subsequent olefination led to the complete C₁₈-carbon framework. While effective, this approach proved lengthy and prompted the development of a direct alkene difunctionalization that relies on borocupration to advance the cycloadduct to the natural products. Late-stage peripheral C–H functionalization facilitated access to all of the known cephanolides in 6–10 steps as well as five recently isolated ceforalides in 8–13 steps.

中文翻译：

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苯并头孢烷类降二萜类化合物的统一全合成：Cephanolides 和 Ceforalides

本文详细介绍了我们对制备 C ₁₈ - 和 C _{19 -}苯类头孢烷类降二萜类化合物的合成研究。在化学网络分析的指导下，该天然产物家族的核心结构是使用迭代交叉耦合以简洁的方式构建的，然后是正式的反电子需求 [4 + 2] 环加成。使用 Mukaiyama 水合和随后的烯化作用使 [4 + 2] 环加合物中的烯烃基团功能化的初步努力导致了完整的 C ₁₈-碳框架。虽然有效，但这种方法被证明是冗长的，并促进了直接烯烃双官能化的发展，这种双官能化依赖于硼铜化将环加合物推进到天然产物中。后期外周 C-H 功能化有助于在 6-10 步内获得所有已知的头孢内酯，以及在 8-13 步内获得五种最近分离的头孢内酯。