['c1ccoc1', 'O=[N+]([O-])c1ccccc1-c1nc[nH]n1', 'O=[N+]([O-])c1ccccc1', 'c1coc(-c2ncn[nH]2)c1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2n[nH]c(-c3ccco3)n2)cc1.