['C=CCN', 'O=Cc1cc2ccccc2c(=O)[nH]1', 'C=CC', 'NC(=O)c1cc2ccccc2c(=O)[nH]1', 'C=CCNC=O', 'O=c1[nH]ccc2ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1[nH]ccc2ccccc12.