['CC(C)(C)C=O', 'Nc1cc(C(=O)O)c(Cl)nn1', 'CC(C)(C)C(N)=O', 'O=C(O)c1ccnnc1Cl', 'O=CO', 'CC(C)(C)C(=O)Nc1ccc(Cl)nn1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccnnc1.