['CO', 'CCn1c(-c2cnn(C)c2)n[nH]c1=S', 'CC', 'COc1nn(C)cc1-c1n[nH]c(=S)[nH]1', 'CCn1cn[nH]c1=S', 'COc1ccn(C)n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is S=c1[nH]nc(-c2cn[nH]c2)[nH]1.