['CC(C)(C)C=O', 'O=C([O-])c1ccccc1O', 'CC(C)(C)C(=O)O', 'O=C([O-])c1ccccc1', 'O=C[O-]', 'CC(C)(C)C(=O)Oc1ccccc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.