['c1cc2c(o1)CCCNC2', 'Cc1cnn2c(C(F)(F)F)nnc2c1C', 'FC(F)F', 'Cc1c(N2CCCc3occc3C2)nn2cnnc2c1C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cc2c(o1)CCCN(c1ccc3nncn3n1)C2.