Using O=[N+]([O-])O, Cc1c(O)ccc2c1CCN(C(=O)OC(C)(C)C)CC2 to produce Cc1c(O)c([N+](=O)[O-])cc2c1CCN(C(=O)OC(C)(C)C)CC2, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.