['O=CN1CCn2ncnc2C1', 'N[C@H]1CCOc2c(F)cccc21', 'c1nc2n(n1)CCNC2', 'O=CN[C@H]1CCOc2c(F)cccc21']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(N[C@H]1CCOc2ccccc21)N1CCn2ncnc2C1.