Using O=C[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO to produce CC1(C)O[C@H]2[C@@H]([C@H]3COC(C)(C)O3)OC(O)[C@H]2O1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.