['C#CC', 'O=C(O)c1cc(O)ccc1[N+](=O)[O-]', 'C#CCO', 'O=C(O)c1ccccc1[N+](=O)[O-]', 'O=CO', 'C#CCOc1ccc([N+](=O)[O-])cc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.