['CO', 'C=CCn1c(-c2ccccc2)c[nH]c1=S', 'C=CC', 'COc1ccc(-c2c[nH]c(=S)[nH]2)cc1', 'COc1ccccc1', 'C=CCn1cc[nH]c1=S']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is S=c1[nH]cc(-c2ccccc2)[nH]1.