['CC1CCC(=O)CC1', 'CC(C)(C)c1nnn[nH]1', 'CC(C)C', 'O=C1CCC(Cn2cnnn2)CC1', 'O=C1CCCCC1', 'Cn1nnnc1C(C)(C)C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1CCC(Cn2cnnn2)CC1.