['CO', 'Cc1cc(C)nc(-n2nc(C)c(C)c2N)n1', 'COC', 'Cc1cc(C)nc(-n2ncc(C)c2N)n1', 'Cc1cc(C)ncn1', 'COCc1n[nH]c(N)c1C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cnc(-n2cccn2)nc1.