['Cc1nnc(N)s1', 'CC(C)(C)NCC=O', 'CC(C)(C)N', 'CC(=O)Nc1nnc(C)s1', 'CC(C)C', 'Cc1nnc(NC(=O)CN)s1', 'Cc1nncs1', 'CC(C)(C)NCC(N)=O']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1nncs1.