['CO', 'CC1CCN(c2c(C=O)cc([N+](=O)[O-])cc2[N+](=O)[O-])CC1', 'CC1CCNCC1', 'COC(=O)c1cc([N+](=O)[O-])cc([N+](=O)[O-])c1', 'COC=O', 'CC1CCN(c2ccc([N+](=O)[O-])cc2[N+](=O)[O-])CC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(N2CCCCC2)cc1.