['CO', 'O=C(/C=c1/[nH]c(=O)/c(=C/c2ccccc2)s1)C1CC1', 'C1CC1', 'COc1ccc(/C=c2\\s/c(=C\\C=O)[nH]c2=O)cc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(/C=c1/[nH]c(=O)/c(=C/c2ccccc2)s1)C1CC1.