Using CC[C@H](NC(=O)OC(C)(C)C)C(=O)N(C)OC, Br[Mg]C1CC1 to produce CC[C@H](NC(=O)OC(C)(C)C)C(=O)C1CC1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.