Studies toward the synthesis of (−)-stenine

Herein is described an application of the acyl nitroso type 2 intramolecular Diels-Alder reaction as a key step in the progress toward the total synthesis of the Stemona alkaloid (-)-stenine. The chiral cycloaddition precursor is rapidly assembled from a cyclohexene intermediate synthesized through an asymmetric, organocatalyzed Robinson annulation. A key selective alkene reduction provides a tricyclic intermediate which could prove useful in the synthesis of the titular natural product. (C) 2015 Elsevier Ltd. All rights reserved.