Divergent synthesis of organophosphate [11C]VX- and [11C]Sarin-surrogates from a common set of starting materials

Radiolabeled 1-[11C]ethyl, 4-nitrophenyl methylphosphonate (VX surrogate) and 2-[11C]-propanyl, 4-nitrophenyl methylphosphonate (sarin surrogate) were developed as organophosphate (OP) tracers. The [11C]ethyl- and [11C]isopropyl-iodide radiolabeled synthons were obtained by temperature controlled, in loop reactions of [11C]CO2 with MeMgBr followed by reduction with LiAlH4, then reaction with HI. Distillation of the [11C]alkyl iodides into a solution of hydrogen (4-nitrophenyl)methylphosphonate and cesium carbonate afforded the desired tracers in >95% radiochemical purity, yields from [11C]CO2 of 1–3% and 1.7–15.1 GBq/mmol molar activities.