['N#CC1(C=O)CCCC1', 'NC(=O)C1CCNCC1', 'N#CC1CCCC1', 'NC(=O)C1CCN(C=O)CC1', 'NC=O', 'N#CC1(C(=O)N2CCCCC2)CCCC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(C1CCCC1)N1CCCCC1.