Using O=C([O-])[O-], CCOC(=O)c1ncc2[nH]c3ccc(C(=O)O)cc3c2c1COC to produce CCOC(=O)c1ncc2[nH]c3ccc(C(=O)OC)cc3c2c1COC, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.