Ethyl phenylglyoxylate-d5 (Ethyl benzoylformate-d5, Phenylglyoxylic acid ethyl ester-d5) is the deuterium labeled Ethyl phenylglyoxylate (HY-W016618). Ethyl phenylglyoxylate (Ethyl benzoylformate), the ethyl ester of phenylglyoxylic acid, is used as a synthetic reagent. Ethyl phenylglyoxylate is also a poor substrate but a potent inhibitor of chicken liver carboxylesterase. Additionally, Ethyl phenylglyoxylate exhibits photoreactivity, where its excited triplet carbonyl can initiate intermolecular hydrogen abstraction, radical coupling and cross-linking reactions[1][2][3].