['CCCC', 'COc1ccc2c(c1)c(=O)oc1cc(O)ccc12', 'CCCCO', 'COc1ccc2c(c1)c(=O)oc1ccccc12', 'CO', 'CCCCOc1ccc2c(c1)oc(=O)c1ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1oc2ccccc2c2ccccc12.