Using O=[N+]([O-])[O-], CCn1cc(C(=O)O)c(=O)c2cc3c(cc21)OCO3 to produce CCn1cc(C(=O)O)c(=O)c2c([N+](=O)[O-])c3c(cc21)OCO3, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.