['NC=O', 'NC(=O)COc1ccc(C=O)cc1[N+](=O)[O-]', 'NC(N)=O', 'O=CCOc1ccc(C=O)cc1[N+](=O)[O-]', 'CC(=O)NC(N)=O', 'O=Cc1ccc(O)c([N+](=O)[O-])c1', 'NC(=O)NC(=O)CO', 'O=Cc1cccc([N+](=O)[O-])c1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.