A palladium-catalyzed route to huperzine A and its analogs and their anticholinesterase activity

Huperzine A is an alkaloid isolated from Huperzia serrata (Thunb.) Trev., a Chinese club moss the extracts of which have been used in Chinese folklore medicine to treat a variety of maladies including memory disorders. Recently, this molecule has attracted widespread attention because of its possible use in the treatment of Alzheimer's disease (AD). We describe herein a palladium-catalyzed bicycloannulation route to this molecule which makes huperzine A available in 40% overall yield. The application of this methodology to seven other huperzine A analogues together with their biological activity in the inhibition of rat cortex acetylcholinesterase (AChE) is detailed herein. None of these new compounds was more potent than the parent structure as AChE inhibitors.