A chiral tricyclic proline analogue obtained from camphor

Synthesis of 3a,6a-dimethylhexahydro-1,4-methanocyclopenta[c]pyrrole-1(2H)-carboxylic acid, a new chiral constrained proline analogue is reported. The synthesis was accomplished in five steps from 8-bromocamphor, easily available in both enantiomeric forms. A key step in the synthesis is an intramolecular ‘domino’-type cyclisation, initiated by a nucleophile attack at an activated CN bond.