['C#CCN', 'N#CC(C=O)C(=O)CCc1cc(F)ccc1F', 'C#CC', 'N#CC(C(N)=O)C(=O)CCc1cc(F)ccc1F', 'Fc1ccc(F)cc1', 'C#CCNC(=O)C(C#N)C(=O)CC']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccccc1.