['CNC', 'Cc1nn(CN2CCc3cc([SH](=O)=O)ccc32)c(=S)n1C', 'Cc1n[nH]c(=S)n1C', 'CN1CCc2cc(S(=O)(=O)N(C)C)ccc21']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is S=c1[nH]cnn1CN1CCc2ccccc21.