['COCC=O', 'Nc1nc2cc(C(F)(F)F)ccc2s1', 'CO', 'CC(=O)Nc1nc2cc(C(F)(F)F)ccc2s1', 'COCC(N)=O', 'FC(F)(F)c1ccc2scnc2c1', 'FC(F)F', 'COCC(=O)Nc1nc2ccccc2s1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2scnc2c1.