['CO', 'Cc1nc(/C=C2\\CCc3ccccc3C2=O)c2ccccn12', 'Cc1nc(C)n2ccccc12', 'COc1ccc2c(c1)CCCC2=O']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C1/C(=C/c2ncn3ccccc23)CCc2ccccc21.