['c1ccc2ccccc2c1', 'O=CC[C@@H]1OC(=O)C(Cl)=C1Cl', 'O=C1OCC(Cl)=C1Cl', 'CC(=O)c1ccc2ccccc2c1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1C=C[C@H](CC(=O)c2ccc3ccccc3c2)O1.