A synthetic approach to the Stemona alkaloids

This paper describes our work developing a strategy for the construction of the typical core structure of the Stemona alkaloids. The approach is to co ntrol the relative stereochemistry of the groups on the core 1-azabicyclo[5 .3.0]decane ring system by a [3,3] sigmatropic rearrangement of an acylimmo nium. ion followed by selective reduction. After optimization, this reactio n sequence afforded the desired diastereomer in 62% yield. Further efforts were directed toward elaboration of the characteristic butyrolactone substi tuent.