Using CC(C)(C)OC(=O)N1CC(C(=O)O)C1, CC1(C)OC(=O)CC(=O)O1 to produce CC(C)(C)OC(=O)N1CC(C(=O)C2C(=O)OC(C)(C)OC2=O)C1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.