['Cn1cncc1C=O', 'O=C1CNCN1CC(F)(F)F', 'Cn1ccnc1', 'O=CN1CC(=O)N(CC(F)(F)F)C1', 'CC(F)(F)F', 'Cn1cncc1C(=O)N1CNC(=O)C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1CN(C(=O)c2cnc[nH]2)CN1.