['CC(=O)O', 'Cc1ccc(-c2cc(Cl)c(C)c([N+](=O)[O-])c2)o1', 'O=C(O)/C=C/c1ccco1', 'Cc1c(Cl)cccc1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2ccco2)cc1.