['CC=O', 'CC1(C(=O)N2CC(N)C2)COC1', 'CC1(C=O)COC1', 'CC(=O)NC1CNC1', 'CC(N)=O', 'CC1(C(=O)N2CCC2)COC1', 'CC1COC1', 'CC(=O)NC1CN(C=O)C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(C1COC1)N1CCC1.