Enantioselective total syntheses of (+)-kobusine, (+)-spirasine IX and the proposed structure of (+)-orgetine were achieved. A unique approach was developed to construct a cage-like hexacyclic ring system that underwent an HAT-initiated radical rearrangement to forge the hetisine-type scaffold. Subsequent late-stage redox manipulations, including an intramolecular hydride shift, were deployed to provide different C20-diterpenoid alkaloids.