['CC(C)(C)O', 'CC1(C)[C@]2(C)CC[C@@]1(NC=O)C(=O)C2=O', 'CC(C)(C)OC=O', 'CC1(C)[C@@]2(N)CC[C@]1(C)C(=O)C2=O', 'CC(C)C', 'CC1(C)[C@]2(C)CC[C@@]1(NC(=O)O)C(=O)C2=O', 'CC(C)(C)OC(N)=O', 'CC1(C)[C@@H]2CC[C@]1(C)C(=O)C2=O']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1C(=O)C2CCC1C2.