['CO', 'CCn1c(-c2ccccc2)c[nH]c1=S', 'CCOC', 'S=c1[nH]cc(-c2ccccc2)[nH]1', 'c1ccccc1', 'COCCn1cc[nH]c1=S']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is S=c1[nH]cc(-c2ccccc2)[nH]1.