['O=[N+]([O-])c1ccccc1', 'Brc1ccc(C2CNCCO2)cc1', 'Brc1ccccc1', 'O=[N+]([O-])c1ccccc1N1CCOCC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(C2CN(c3ccccc3)CCO2)cc1.