['CO', 'CCOCCNc1ncnc2nc[nH]c12', 'CCOC', 'OCCNc1ncnc2nc[nH]c12', 'COCCO', 'CCNc1ncnc2nc[nH]c12', 'CCOCCOC', 'Nc1ncnc2nc[nH]c12', 'COCCOCCN', 'c1ncc2[nH]cnc2n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ncc2[nH]cnc2n1.