['CCO', 'O=CCc1cc(=O)oc2cc(O)cc(O)c12', 'CC', 'O=C(O)Cc1cc(=O)oc2cc(O)cc(O)c12', 'CCOC(C)=O', 'O=c1ccc2c(O)cc(O)cc2o1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1ccc2ccccc2o1.