['CC(C)(C)O', 'NNC(=O)CCCCCNC=O', 'CC(C)(C)OC=O', 'NCCCCCC(=O)NN', 'CC(C)C', 'NNC(=O)CCCCCNC(=O)O', 'CC(C)(C)OC(N)=O', 'CCCCCC(=O)NN']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is None.