['CC=O', 'O=C(C1CC=CCC1)N1CCNCC1', 'O=CC1CC=CCC1', 'CC(=O)N1CCNCC1', 'C1=CCCCC1', 'CC(=O)N1CCN(C=O)CC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(C1CC=CCC1)N1CCNCC1.