['CCO', 'O=CNNC(=O)Cn1ccc(=O)c2ccccc21', 'CC', 'O=C(O)NNC(=O)Cn1ccc(=O)c2ccccc21', 'CCOC(=O)NNC(C)=O', 'O=c1cc[nH]c2ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1cc[nH]c2ccccc12.