Using O=C1CCC(=O)N1Br, Cc1nc2cc3c(cc2c(=O)n1COC(=O)C(C)(C)C)CCC3 to produce Cc1nc2cc3c(cc2c(=O)n1COC(=O)C(C)(C)C)C(Br)CC3, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.