['Cn1ccs/c1=N\\C=O', 'Cc1ccnn1-c1ccccc1F', 'Fc1ccccc1', 'Cc1[nH]ncc1C(=O)/N=c1\\sccn1C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(/N=c1/[nH]ccs1)c1cnn(-c2ccccc2)c1.