['CO', 'CC1(C)[C@]2(C=O)CC[C@@]1(CBr)C(=O)C2', 'COC=O', 'CC1(C)[C@H]2CC[C@@]1(CBr)C(=O)C2', 'CBr', 'COC(=O)[C@@]12CC[C@H](C(=O)C1)C2(C)C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1CC2CCC1C2.