Using CCO, CCCc1c(O)c(C(C)=O)cc2c(NCC)cc(C(=O)O)nc12 to produce CCCc1c(O)c(C(C)=O)cc2c(NCC)cc(C(=O)OCC)nc12, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.