['O=C[C@H]1CCC(=O)N1', 'CNC1CC2CCC(C1)N2C', 'CN1C2CCCC1CC2', 'CNC(=O)[C@H]1CCC(=O)N1', 'O=C1CCCN1', 'CN(C=O)C1CC2CCC(C1)N2C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1CC[C@H](C(=O)NC2CC3CCC(C2)N3)N1.