A Concise Asymmetric Route to Nuphar Alkaloids. A Formal Synthesis of (−)-Deoxynupharidine

A stereocontrolled route to Nuphar alkaloids is described that employs a formal [3 + 3] cycloaddition strategy to assemble the piperidine nucleus. The addition of Pd−TMM complexes to aziridine 10 was found to be sluggish; however, the addition of a functionalized allyl Grignard reagent followed by a Mitsunobu condensation reaction provided 11 in high yield. The employment of this route in the formal synthesis of (−)-deoxynupharidine 1 is described.