['CC1(C)CNC1C1CC1', 'Cn1cc2c(n1)CCCC2C=O', 'C1CC1', 'Cn1cc2c(n1)CCCC2C(=O)N1CC(C)(C)C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(C1CCCc2n[nH]cc21)N1CCC1C1CC1.