['CC1(C)CNCC2(CCCC2)O1', 'FC(F)(F)c1nnc2cccnn12', 'FC(F)F', 'CC1(C)CN(c2ccc3nncn3n2)CC2(CCCC2)O1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cc2nncn2nc1N1CCOC2(CCCC2)C1.