Using COC(=O)c1cc(-c2cccs2)c(C(=O)OC)cc1-c1cccs1 to produce O=C(O)c1cc(-c2cccs2)c(C(=O)O)cc1-c1cccs1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.