['CC(C)CN', 'O=CCCn1nnc2ccccc2c1=O', 'CC(C)C', 'NC(=O)CCn1nnc2ccccc2c1=O', 'CCC(=O)NCC(C)C', 'O=c1[nH]nnc2ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1[nH]nnc2ccccc12.