Synthesis of wilsoniamines A and B

A two-step synthesis of marine origin brominated alkaloids wilsoniamines A ( 1 ) and B ( 2 ), isolated from Australian bryozoan Amathia wilsoni Kirkpatrick, possessing a novel hexahydro-1 H -pyrrolo[1,2- c ]imidazol-1-one ring system is described. The core hexahydro-1 H -pyrrolo[1,2- c ]imidazol-1-one ring systems is constructed through a condensation reaction between (2,4,6-tribromo-3-methoxyphenyl)acetaldehyde and ( S )- N -methylpyrrolidine-2-carboxamide as key steps. The orientation of substituted benzyl side-chain in the two epimeric natural products was controlled by carrying out the key condensation reaction under kinetic or thermodynamic conditions.