N-[(S)-(4-nitrophenoxy)phenoxyphosphinyl]-L-Alanine 2-ethylbutyl ester (also known as Remdesivir Impurity 4)is a phosphoramidate sidechain typically used for the preparation of GS-5734, which is a novel antiviral investigational drug originally for the treatment of Ebola virus disease and Marburg virus infections and has subsequently also been found to show antiviral activity against coronaviruses (e.g. SARS-Cov-2/Covid-19).
Discovery and Synthesis of a Phosphoramidate Prodrug of a Pyrrolo[2,1-f][triazin-4-amino] Adenine C-Nucleoside (GS-5734) for the Treatment of Ebola and Emerging Viruses. 
 D.Siegel, et al, J. Med. Chem., 2017, 60(5), pp 1648-1661.
Not classified as hazardous substance or mixture
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