Using O=C(O)CC1CCc2cc(C(=O)c3ccccc3)c(O)cc21, CO to produce COC(=O)CC1CCc2cc(C(=O)c3ccccc3)c(O)cc21, please predict the solvent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.