['C=CC', 'O=C(O)c1cc([N+](=O)[O-])ccc1O', 'C=CCO', 'O=C(O)c1cccc([N+](=O)[O-])c1', 'O=CO', 'C=CCOc1ccc([N+](=O)[O-])cc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.