['O=CN1CCn2ccnc2C1', 'N[C@H]1CCOc2c(F)cccc21', 'c1cn2c(n1)CNCC2', '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)N1CCn2ccnc2C1.