['CNCC=O', 'Nc1cccc([N+](=O)[O-])c1', 'CN', 'CC(=O)Nc1cccc([N+](=O)[O-])c1', 'CNCC(N)=O', 'O=[N+]([O-])c1ccccc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.