A Nine-Step Formal Synthesis of (±)-Morphine.

A nine-step stereoselective formal synthesis of (±)-morphine from readily available o-vanillin is presented. The carbocyclic structure of morphine was quickly assembled through an orchestration of the intermolecular Diels-Alder/Claisen/Friedel-Crafts sequential reaction. This approach involves many one-pot procedures and no protecting groups, and only a few chromatographic purifications are required.