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