['Fc1ccccc1', 'O=CNNC(=O)Cc1ccccc1[N+](=O)[O-]', 'O=[N+]([O-])c1ccccc1', 'CC(=O)NNC(=O)c1ccccc1F']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(Cc1ccccc1)NNC(=O)c1ccccc1.