['CC', 'CCNc1c([N+](=O)[O-])cc(C(N)=O)cc1[N+](=O)[O-]', 'CCNCC', 'NC(=O)c1cc([N+](=O)[O-])cc([N+](=O)[O-])c1', 'NC=O', 'CCN(CC)c1c([N+](=O)[O-])cccc1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.