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-1H-pyrrolo[1,2-c]imidazol-1-one ring system is described. The core hexahydro-1H-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.