['CC=O', 'CC1CCN(C(=O)N2CCNCC2)C1', 'CC1CCN(C=O)C1', 'CC(=O)N1CCNCC1', 'CC1CCNC1', 'CC(=O)N1CCN(C=O)CC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(N1CCCC1)N1CCNCC1.