['CO', 'O=Cc1cnc(N2CCCC2)[nH]c1=O', 'C1CCNC1', 'COC(=O)c1cnc[nH]c1=O', 'COC=O', 'O=c1ccnc(N2CCCC2)[nH]1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1ccnc(N2CCCC2)[nH]1.