['C1CCNC1', 'O=[N+]([O-])c1cncnc1NC1CC1', 'NC1CC1', 'O=[N+]([O-])c1cnc(N2CCCC2)nc1', 'C1CC1', 'Nc1nc(N2CCCC2)ncc1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cc(NC2CC2)nc(N2CCCC2)n1.