Using CNS(=O)(=O)c1cc2c(c(C(=O)O)c1)OCCO2, O=C([O-])[O-] to produce CNS(=O)(=O)c1cc2c(c(C(=O)OC)c1)OCCO2, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.