['OCCC1CNC1', 'CC(C)(C=O)N1CCOCC1', 'C1COCCN1', 'CC(C)C(=O)N1CC(CCO)C1', 'CCO', 'CC(C)(C(=O)N1CCC1)N1CCOCC1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(CN1CCOCC1)N1CCC1.