['CCC', 'Cc1n[nH]cc1C1NC(=O)[C@@H]2[C@@H](C)OCCN12', 'Cc1ccn(C(C)C)n1', 'C[C@H]1OCCN2CNC(=O)[C@H]12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1NC(c2cn[nH]c2)N2CCOC[C@@H]12.