['c1ccccc1', 'O=c1[nH]nc(C2CC2)c2cn[nH]c12', 'C1CC1', 'O=c1[nH]ncc2cnn(-c3ccccc3)c12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1[nH]nc(C2CC2)c2cnn(-c3ccccc3)c12.