['C=CCN', 'CS(=O)(=O)c1nc(C=O)c2ccccn12', 'C=CC', 'CS(=O)(=O)c1nc(C(N)=O)c2ccccn12', 'C=CCNC=O', 'CS(=O)(=O)c1ncc2ccccn12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccn2cncc2c1.