The marine sponge alkaloid stevensine (3) has been synthesized from the related C 1 1 N 5 alkaloid, hymenin (1). The key transformation involves a regioselective protodebromination/transbromination event of 4 -bromohymenin (2) to install the olefin in 3. Such processes are seldom used for synthetic purposes but appear to be highly applicable to the C 1 1 N 5 family of marine alkaloids.