['CCO', 'Cc1c(Cl)cc(C=O)cc1[N+](=O)[O-]', 'CC', 'Cc1c(Cl)cc(C(=O)O)cc1[N+](=O)[O-]', 'CCOC=O', 'Cc1c(Cl)cccc1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.