['CCO', 'Nc1c(C=O)cnc2c(Cl)cc([N+](=O)[O-])cc12', 'CC', 'Nc1c(C(=O)O)cnc2c(Cl)cc([N+](=O)[O-])cc12', 'CCOC=O', 'Nc1ccnc2c(Cl)cc([N+](=O)[O-])cc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2ncccc2c1.