5-epi Emtricitabine-13C,15N2 is a labelled analogue of 5-epi Emtricitabine (E524980). 5-epi Emtricitabine is an epimer of Emtricitabine (E525000), a nucleoside reverse transcriptase inhibitor approved for treatment of human immunodeficiency virus (HIV) 1, and also has antagonistic activity against the hepatitis B virus. 5-epi Emtricitabine is also used as a reagent for the synthesis of β-L-(2R,5S)- and α-L-(2R,5R)-1,3-oxathiolane-pyrimidine and -purine nucleosides as potential HIV agents.