Using COC(=O)C1=CC2=C(C(=O)c3ccccc3C2=O)C(OC)S1 to produce COC1SC(C(=O)O)=CC2=C1C(=O)c1ccccc1C2=O, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.