['C=CC', 'CC(C)(C)c1nnc2sc(N)nn2c1=O', 'C=CCN', 'CC(C)(C)c1nnc2scnn2c1=O', 'CC(C)C', 'C=CCNc1nn2c(=O)cnnc2s1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1cnnc2scnn12.