Using CCOC(CC(C(=O)OC)C(=O)OC)OCC, CCOC(CBr)OCC to produce CCOC(CC(CC(OCC)OCC)(C(=O)OC)C(=O)OC)OCC, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.