['C[C@H]1OCC[C@H]1N', 'CCN1CCNC1=O', 'C[C@@H]1CCCO1', 'NCCN1CCNC1=O', 'O=C1NCCN1', 'CCN[C@@H]1CCO[C@@H]1C']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1NCCN1CCN[C@@H]1CCOC1.