['CCO', 'CNc1cc(C)nc2nc(C(F)(F)F)nn12', 'CNCCO', 'Cc1ccn2nc(C(F)(F)F)nc2n1', 'FC(F)F', 'Cc1cc(N(C)CCO)n2ncnc2n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cnc2ncnn2c1.