['CC(N)=O', 'O=[N+]([O-])c1cc(-c2ccccc2)ccc1O', 'NC(=O)CO', 'O=[N+]([O-])c1cccc(-c2ccccc2)c1', 'c1ccccc1', 'NC(=O)COc1ccccc1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2ccccc2)cc1.