Concise Synthesis of (.+-.)-Cytisine via Lithiation of N-Boc-bispidine.

(±)-Cytisine has been synthesized in 19% overall yield via a six-step approach from commercially available materials. Key features of this new strategy are as follows:  (i) initial construction of the bispidine core, (ii) lithiation−transmetalation−allylation of an N-Boc-bispidine, and (iii) a Pd/C-mediated dihydropyridone oxidation−N-debenzylation process.