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