Azomethine Ylide Cycloaddition Approach toward Dendrobine: Synthesis of 5‑Deoxymubironine C

A concise route to the azatricyclo­[6.2.1.04,11]­undecane core of (−)-dendrobine and (−)-mubironine C is described wherein an unstabilized azomethine ylide cycloaddition provides the complete carbon framework of the natural products. The cyclization precursor is made in short order from (R)-carvone through an unconventional high-pressure Ireland–Claisen reaction. Attempts to install a final hydroxyl group through an intramolecular lactonization strategy and the observation of an unexpected and highly complex enal–ene product are also reported.