Divergent Total Syntheses of Lyconadins A and C

Divergent and concise total syntheses of two lycopodium alkaloids, lyconadinsA and C have been developed. The synthesis of lyconadinA, having potent neurotrophic activity, features an efficient one-pot ketal removal and formal aza-[4+2] cyclization to form the cagelike core structure. A tandem ketal removal/Mannich reaction was developed to build the tricyclic structure of lyconadinC. Both lyconadinsA and C were synthesized from a pivotal intermediate.