4-[4-(2-Propyn-1-yloxy)benzoyl]benzoic Acid Methyl Ester is an intermediate in the synthesis of 4-[4-(2-Propyn-1-yloxy)benzoyl]benzoic Acid (P838505), which is a benzophenone residue used for Protein Photolabeling. 4-[4-(2-Propyn-1-yloxy)benzoyl]benzoic Acid can also be used for the synthesis of new Thiodigalactoside-Based chemical probes to label galectin-3.