['C[C@@H]1CNC[C@@H](C)O1', 'O=CCn1ncc2ccccc2c1=O', 'CC(=O)N1C[C@@H](C)O[C@H](C)C1', 'O=c1[nH]ncc2ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(Cn1ncc2ccccc2c1=O)N1CCOCC1.