['O=CC[C@@H]1NC(=O)NC1=O', 'Oc1ccc2c(c1)OCCNC2', 'O=C1CNC(=O)N1', 'CC(=O)N1CCOc2cc(O)ccc2C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1NC(=O)[C@H](CC(=O)N2CCOc3ccccc3C2)N1.