((4S)-4-Cyclohexyl-1-[(R)-[(S)-1-hydroxy-2-methylpropoxy](4-phenylbutyl)phosphinyl]acetyl-D-proline Propionate (ester) Hemibarium Salt Sesquihydrate) is an impurity in the synthesis of Fosinopril (F727800), a phosphinic acid containing angiotensin converting enzyme (ACE) inhibitor. Antihypertensive.
