Herein is reported a concise synthesis of spiro-annulated cyclobutane tetracyclic and pentacyclic derivatives by ketene addition, and ring-rearrangement metathesis (RRM) as key steps, starting with commercially available norbornadiene and dicyclopentadiene. The tetracyclic spiro-derivative contains a [5/5/4] core unit, which is the key building block to angular triquinanes synthesis. Whereas, the pentacyclic spiro-derivative contains a basic core skeleton of presilphiperfolanes, and other sesquiterpenoids.

中文翻译：

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通过烯酮[2 + 2]环加成和环重整易位合成螺环化环丁烷衍生物

本文报道了通过烯酮加成和环重排易位（RRM）作为关键步骤的螺环化环丁烷四环和五环衍生物的简明合成，从市售降冰片二烯和二环戊二烯开始。四环螺环衍生物包含[5/5/4]核心单元，这是角三喹烷合成的关键组成部分。而五环螺环衍生物含有前银环戊烷和其他倍半萜的基本核心骨架。