['CNC', 'Cn1cnn(CN2CCc3cc([SH](=O)=O)ccc32)c1=S', 'Cn1cn[nH]c1=S', 'CN1CCc2cc(S(=O)(=O)N(C)C)ccc21']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is S=c1[nH]cnn1CN1CCc2ccccc21.