['CO', 'CC1(S(=O)(=O)N2CCc3cnccc32)CC1', 'c1cc2c(cn1)CCN2', 'COCC1([SH](=O)=O)CC1', 'COC', 'O=S(=O)(C1CC1)N1CCc2cnccc21']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=S(=O)(C1CC1)N1CCc2cnccc21.