A robust and scalable synthesis of the potent neuroprotective agent (-)-huperzine A

(-)-Huperzine A (1) is a tricyclic alkaloid that is produced in low yield by the Chinese herb Huperzia serrata. There is intense contemporary interest in clinical application of (-)-huperzine A (1) for treating neurodegenerative diseases and protecting against the lethal effects of chemical warfare agents, such as sarin and VX. We report a robust, scalable, and efficient synthesis of (-)-huperzine A (1) from (R)-4-methyl-cyclohex-2-ene-1-one (5). Our route proceeds in 35-45% overall yield, delivers (-)-huperzine A (1) in only eight steps from cyclohexenone 5, requires only three chromatographic purifications, and can provide gram quantities of the target. This route represents a critical, enabling advance toward detailed evaluation of (-)-huperzine A (1) in clinical settings.