Using COC(=O)[C@@H]1CCCN1C(=O)OC(C)(C)C, O=[Cr](=O)([O-])O[Cr](=O)(=O)[O-] to produce COC(=O)C1CC(=O)CN1C(=O)OC(C)(C)C, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.