['Cc1nnn(C)n1', 'CCC1(C)CC(=O)NC1=O', 'Cn1ncnn1', 'CCC1(C)CC(=O)N(C)C1=O', 'CC', 'CC1CC(=O)N(Cc2nnn(C)n2)C1=O']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1CCC(=O)N1Cc1nn[nH]n1.