Using CC(=O)OC(C)c1cc2c(s1)C(=O)c1ccsc1C2=O to produce CC(=O)OC(C)c1cc2c(s1)C(=O)c1c(C(C)OC(C)=O)csc1C2=O, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.