['CO', 'Nc1c(C=O)cnn1-c1ccc(Cl)cc1', 'COC=O', 'Nc1ccnn1-c1ccc(Cl)cc1', 'Clc1ccccc1', 'COC(=O)c1cn[nH]c1N']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-n2cccn2)cc1.