Using COCc1ccc2c(c1C(=O)OC)OC[C@H]1[C@@H]2C1(Br)Br to produce COCc1ccc2c(c1C(=O)OC)OC[C@@H]1C[C@H]21, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.