['CO', 'CCCc1nn(C)c(N)c1-c1ccccc1', 'CCC', 'COc1ccccc1-c1cnn(C)c1N', 'COc1ccccc1', 'CCCc1cc(N)n(C)n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2cn[nH]c2)cc1.