Synthesis and Structural Elucidation of Nitrosamine Impurities in Active Pharmaceutical Ingredients

Nitrosamine impurities have become an important concern in the pharmaceutical industry because of their potential mutagenic and carcinogenic risks. The present study reports the synthesis, isolation, and structural characterization of three representative nitrosamine drug substance-related impurities (NDSRIs): N-nitroso tadalafil, N-nitroso ciprofloxacin, and N-nitroso ticagrelor. These impurities were synthesized through controlled nitrosation of the corresponding drug substances using sodium nitrite or tert-butyl nitrite under optimized reaction conditions. The crude products were purified by chromatographic techniques to obtain the desired nitrosamine impurities with suitable purity. Structural confirmation was carried out using high-performance liquid chromatography (HPLC), mass spectrometry (MS), and 1H nuclear magnetic resonance (1H NMR) spectroscopy. The analytical results verified the successful formation and identity of all three target compounds. The developed synthetic procedures and comprehensive characterization data provide valuable reference materials for impurity profiling, analytical method development, reference standard preparation, and toxicological evaluation. This work also contributes to regulatory investigations and risk assessment related to nitrosamine contamination in active pharmaceutical ingredients, supporting the development of safer pharmaceutical products.