['CC=O', 'O=C(C1CNC1)N1CC(O)C2(CC2)C1', 'OC1CNCC12CC2', 'CC(=O)N1CC(C=O)C1', 'CC(=O)N1CCC1', 'O=CN1CC(O)C2(CC2)C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(C1CNC1)N1CCC2(CC2)C1.