['C1CC2(CCN1)OCCO2', 'CC(=O)c1cccc([N+](=O)[O-])c1', 'CC=O', 'O=[N+]([O-])c1ccccc1N1CCC2(CC1)OCCO2']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(N2CCC3(CC2)OCCO3)cc1.