['O=c1[nH]ccc2c1CNCC2', 'O=C1CCCCN1CC(F)(F)F', 'CC(F)(F)F', 'O=C1NCCCC1N1CCc2cc[nH]c(=O)c2C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1NCCCC1N1CCc2cc[nH]c(=O)c2C1.