Pa. Wender et al., Asymmetric synthesis of the tricyclic core of NGF-inducing cyathane diterpenes via a transition-metal-catalyzed [5+2] cycloaddition, ORG LETT, 3(13), 2001, pp. 2105-2108
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A concise asymmetric synthesis of the tricyclic core of cyathane diterpenes
is described, based on a novel transition-metal-catalyzed intramolecular [
5 + 2] cycloaddition of ynone-vinylcyclopropane 10 (assembled from commerci
ally available (S)-(-)-limonene), which proceeds in 90% yield with > 95% se
lectivity. This strategy provides efficient access (14 steps and 13% overal
l yield) to potential analogues as well as precursors of nerve growth facto
r (NGF)-inducing diterpenes.