['CC=O', 'CC(C)(C)c1nc2ccc(N)cc2[nH]1', 'CC(N)=O', 'CC(C)(C)c1nc2ccccc2[nH]1', 'CC(C)C', 'CC(=O)Nc1ccc2nc[nH]c2c1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2[nH]cnc2c1.