['CO', 'Cc1ccc(-n2nc(C(=O)O)ccc2=O)cc1', 'O=CO', 'COc1cnn(-c2ccc(C)cc2)c(=O)c1', 'Cc1ccccc1', 'COc1cc(=O)[nH]nc1C(=O)O']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1cccnn1-c1ccccc1.