Phenylmethyl (3α,5β,6E)-6-Ethylidene-3-hydroxy-7-oxo-cholan-24-oic Acid Ester-d4 is an intermediate used in the synthesis of 6-Ethylchenodeoxycholic-d5 Acid (E899812), which is an isotope labelled compound of 6-Ethylchenodeoxycholic Acid (E899810), which is used in the investigative treatment of primary biliary cholangitis. Primary biliary cholangitis is an autoimmune disease of the liver that slowly progresses to cirrhosis.