The polysubstituted and spirocyclic cyclobutanes were efficiently constructed by the utilization of a novel skeletal contraction strategy which only took one-step synthesis from the readily accessible pyrrolidines. The mechanistic studies indicated that a key intermediate N-aminated pyrrolidine was formed initially and subsequent extrusion of a nitrogen via a radical pathway completed the transformation. This practical methodology was further highlighted by the concise, formal synthesis of the cytotoxic natural product piperarborenine B.

中文翻译：

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骨骼收缩：获得多取代环丁烷的新策略

多取代和螺环环丁烷是通过利用一种新的骨架收缩策略有效地构建的，该策略只需要从容易获得的吡咯烷中一步合成。机理研究表明，最初形成了一个关键的中间体 N-胺化吡咯烷，随后通过自由基途径挤出氮完成了转化。这种实用的方法通过细胞毒性天然产物 piperarborenine B 的简明、正式合成进一步突出。