Total Synthesis of Huperzine R.

A total synthesis of huperzine R was accomplished. Intramolecular cycloaddition of a nitrile oxide and reductive cleavage of the resulting isoxazoline induced sequential cleavage of the C-C and C-O bonds to form the characteristic bicyclic lactam core with an enone moiety. Construction of the butenolide moiety from the enone afforded huperzine R.