['CCCC=O', 'c1cnn(CCN2CCNCC2)c1', 'CCn1cccn1', 'CCCC(=O)N1CCNCC1', 'c1cn[nH]c1', 'CCCC(=O)N1CCN(CC)CC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cnn(CCN2CCNCC2)c1.