Syntheses of (+)-Complanadine A and Lycodine Derivatives by Regioselective [2 + 2 + 2] Cycloadditions

The dimeric alkaloid complanadine A has shown promise in regenerative science, promoting neuronal growth by inducing the secretion of growth factors from glial cells. Through the use of tandem, cobalt-mediated [2 + 2 + 2] cycloaddition reactions, two synthetic routes have been developed with different sequences for the formation of the unsymmetric bipyridyl core. The regioselective formation of each of the pyridines was achieved based on the inherent selectivity of the molecules or by reversing the regioselectivity through the addition of Lewis bases. This strategy has been successfully employed to provide laboratory access to complanadine A as well as structurally related compounds possessing the lycodine core.