['O=[N+]([O-])c1ccccn1', 'O=C1OCC[C@H]1N1CCNCC1', 'O=C1CCCO1', 'O=[N+]([O-])c1ccc(N2CCNCC2)cn1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1OCC[C@H]1N1CCN(c2cccnc2)CC1.