['CCCCCCC', 'Nc1ccc2nnc(C(F)(F)F)n2n1', 'CCCCCC(C)N', 'FC(F)(F)c1nnc2cccnn12', 'FC(F)F', 'CCCCCC(C)Nc1ccc2nncn2n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cnn2cnnc2c1.