['C[C@@H]1CCCCN1', 'NC(=O)c1cc([N+](=O)[O-])cc([N+](=O)[O-])c1', 'NC=O', 'C[C@@H]1CCCCN1c1c([N+](=O)[O-])cccc1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(N2CCCCC2)cc1.