['CCCC(C)N', 'O=CCn1ccc(=O)c2ccccc21', 'CCCCC', 'NC(=O)Cn1ccc(=O)c2ccccc21', 'CCCC(C)NC(C)=O', 'O=c1cc[nH]c2ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1cc[nH]c2ccccc12.