['CO', 'O=Cc1cc([N+](=O)[O-])cc([N+](=O)[O-])c1N1CCCC1', 'C1CCNC1', 'COC(=O)c1cc([N+](=O)[O-])cc([N+](=O)[O-])c1', 'COC=O', 'O=[N+]([O-])c1ccc(N2CCCC2)c([N+](=O)[O-])c1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(N2CCCC2)cc1.