Synthesis of Conjugates of the Alkaloids Cytisine and Lupinine

A Pyridine Dearomatization Approach for the Gram Scale Synthesis of (±)-Sparteine

Both enantiomers of sparteine have suffered from pricing and supply chain variability, which has inspired efforts toward efficient chemical synthesis. Here, we build upon our reported synthesis of the matrine-type lupin alkaloids in order to synthesize (±)-sparteine. Specifically, selective quenching of the cyclization between glutaryl chloride and pyridine with methanol provides a functionalized quinolizidine core that was elaborated to (±)-sparteine in six additional steps on gram scale. This synthesis provides a scalable route to sparteine from inexpensive commodity chemicals utilizing a dearomative cyclization. In addition, this route provides concise access to (±)-lupinine.