Total syntheses of dimmeric lycopodium alkaloid, complanadines A and B

Our total syntheses of lycopodium alkaloid lycodine (1), and its unsymmetric dimmer complanadines A (3) and B (4) were described. The bicyclo [3.3.1]nonane core structure of lycodine was constructed by regioselective Diels-Alder and intramolecular Mizoroki-Heck reactions. A late-stage coupling reaction of the lycodine units, pyridine N-oxide (+)-17 and aryl bromide (+)-16, through C-H arylation at the C1 position of (+)-17 provided the unsymmetric dimer structure. This strategy significantly simplified the construction of the dimeric architecture and functionalization. Total syntheses of complanadines A (3) and B (4) were achieved by adjusting the oxidation level of the bipyridine mono-N-oxide (+)-18. The diverse utility of this common intermediate (+)-18 suggests a possible biosynthetic pathway of complanadines in nature. Both enantiomers of lycodine (1) and complanadines A (3) and B (4) were prepared in sufficient quantities. The effect on neuron differentiation of PC-12 cells with human astrocytoma cells culture medium was evaluated.