['CO', 'C[C@H](NC=C(C#N)C#N)c1cc2ccccc2o1', 'N#CC(C#N)=CN', 'CCc1cc2cccc(OC)c2o1', 'CCNC=C(C#N)C#N', 'COc1cccc2ccoc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2occc2c1.