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<p>Bufogargarizins are a class of unique 19-norbufadienolides isolated from the venom of <i>Bufo bufo gargarizans</i>. Here we report a concise synthesis of bufogargarizin B from inexpensive, commercially available dehydroepiandrosterone by means of a conformation-controlled skeletal reorganization approach. The synthesis features the rapid construction of the 5/7/6/5 tetracyclic core framework by means of a SmI<sub>2</sub>-mediated ketone–allylic acetate transannular cyclization, and the installation of stereochemically diverse 5,7- and 7,5-fused ring systems through a biomimetic retro-aldol/transannular aldol cascade reaction. In addition, an efficient, scalable synthesis of 2-pyrone-5-boronate, a key building block for the introduction of the side chain of bufadienolides, has been developed, and the highly functionalized all-<i>cis</i> D ring of bufogargarizin B is installed by means of a series of highly chemo- and regioselective redox transformations. This work vividly demonstrates that conformational control plays a critical role in the precise installation of desired stereocenters in transannular cyclization products.</p>

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Concise synthesis of bufogargarizin B by a conformation-controlled skeletal reorganization approach

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月19日

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  • Peicheng Yang,
  • Yi Shen,
  • Jinghan Gui

摘要

Bufogargarizins are a class of unique 19-norbufadienolides isolated from the venom of Bufo bufo gargarizans. Here we report a concise synthesis of bufogargarizin B from inexpensive, commercially available dehydroepiandrosterone by means of a conformation-controlled skeletal reorganization approach. The synthesis features the rapid construction of the 5/7/6/5 tetracyclic core framework by means of a SmI2-mediated ketone–allylic acetate transannular cyclization, and the installation of stereochemically diverse 5,7- and 7,5-fused ring systems through a biomimetic retro-aldol/transannular aldol cascade reaction. In addition, an efficient, scalable synthesis of 2-pyrone-5-boronate, a key building block for the introduction of the side chain of bufadienolides, has been developed, and the highly functionalized all-cis D ring of bufogargarizin B is installed by means of a series of highly chemo- and regioselective redox transformations. This work vividly demonstrates that conformational control plays a critical role in the precise installation of desired stereocenters in transannular cyclization products.