['CCO', 'O=C[C@H]1Cc2nc(Cl)ccc2C1=O', 'CC', 'O=C(O)[C@H]1Cc2nc(Cl)ccc2C1=O', 'CCOC=O', 'O=C1CCc2nc(Cl)ccc21']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1CCc2ncccc21.