body fluids Tenofovir may be measured in plasma by liquid chromatography. Such testing is useful for monitoring therapy and to prevent drug accumulation and toxicity in people with kidney or liver problems. Chemistry Tenofovir is a derivative of adenine and this was the chemical starting point for its first published synthesis which was included in patents to the compound. During drug development, attention switched to the phosphonate ester derivative, tenofovir disoproxil, which was the subject of extensive process chemistry to provide a viable manufacturing route. Adenine is first reacted with a chiral version of propylene carbonate with R absolute configuration, using sodium hydroxide as base. Under these conditions, the reaction is regioselective, with alkylation occurring exclusively in the imidazole ring and at the less-hindered carbon of the dioxolane. In the second step, the hydroxyl group is reacted with a phosphonic acid derivative, using tert-butyllithium as base to ensure selective O-alkylation, with the formation of an ether bond. Tenofovir is formed when the diethyl phosphonate group is converted to its acid using trimethylsilyl chloride in the presence of sodium bromide, a further refinement of the original manufacturing route. The synthesis of the alternative ester in tenofovir disoproxil is completed by alkylation with the appropriate chloromethyl ether derivative and this may be purified as its fumarate salt. History Tenofovir was initially synthesized by Antonín Holý at the Institute of Organic Chemistry and Biochemistry of the Czechoslovak Academy of Sciences in Prague. The patent filed in 1986 makes no mention of the potential use of the compound for the treatment of HIV infection but claims activity against herpes simplex virus. In 1985, De Clercq and Holý described the activity of PMPA against HIV in cell culture. Shortly thereafter, a collaboration with the biotechnology company Gilead Sciences led to the investigation of PMPA's potential as a treatment for HIV infected patients. In 1997 researchers from Gilead and the University of California, San Francisco demonstrated that tenofovir exhibits anti-HIV effects in humans when dosed by subcutaneous injection. The initial form of tenofovir used in these studies had limited potential for widespread use because it poorly penetrated cells and was not absorbed when given by mouth. Gilead developed a pro-drug version of tenofovir, tenofovir disoproxil. This version of tenofovir is often referred to simply as "tenofovir". In this version of the drug, the two negative charges of the tenofovir phosphonic acid group are masked, thus enhancing