['c1ccccc1', 'O=[N+]([O-])c1ccc(-c2c[n+]3c([nH]2)SCC3)cc1', 'O=[N+]([O-])c1ccccc1', 'c1ccc(-n2cc[n+]3c2SCC3)cc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2c[n+]3c(n2-c2ccccc2)SCC3)cc1.