N2-(S)-1-Ethoxycarbonyl-3-phenyl-d5-propyl-N8-trifluoroacetyl-L-lysine is the labeled analogue of N2-(S)-1-Ethoxycarbonyl-3-phenylpropyl-N8-trifluoroacetyl-L-lysine (E891650), an intermediate in the synthesis of lisinopril (L468985), an orally active angiotensin-converting enzyme (ACE) inhibitor.