['CO', 'Cc1ncncc1Cn1cnc(C#N)n1', 'N#Cc1nc[nH]n1', 'COc1ncc(C)c(C)n1', 'Cn1cnc(C#N)n1', 'COc1nccc(C)n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ncc(Cn2cncn2)cn1.