Using COC(=O)CC(CCO)n1c(=O)n(Cc2csc3cccc(C)c23)c2ccccc21, O=[Cr](=O)([O-])O[Cr](=O)(=O)[O-] to produce COC(=O)CC(CC(=O)O)n1c(=O)n(Cc2csc3cccc(C)c23)c2ccccc21, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.