Using COC(=O)COc1cccc2c(CNC(=O)COc3ccccc3)coc12 to produce O=C(O)COc1cccc2c(CNC(=O)COc3ccccc3)coc12, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.