Fosinopril is an angiotensin-converting enzyme (ACE) inhibitor and a phosphonate ester prodrug that is hydrolyzed to its active form, fosinoprilat. As a specialty chemical and active pharmaceutical ingredient (API), it is primarily used in pharmaceutical formulations for the treatment of hypertension and congestive heart failure. It works by inhibiting ACE, which reduces angiotensin II production, leading to vasodilation and decreased blood pressure. This high-purity reference standard (≥98%) is suitable for analytical, research, and quality control applications in pharmaceutical development, confirmed by infrared spectroscopy, NMR, and purity assays (97.5-100%). It is not intended for direct clinical use.