R. H. Yu, L. M. Schultze, J. Rohloff
1999
Citations
1
Influential Citations
12
Citations
Journal
Organic Process Research & Development
Abstract
9-[2-(Diethylphosphonomethoxy)ethyl]adenine (diethyl-PMEA), a key intermediate in the production of the antiviral drug adefovir dipivoxil, was originally produced via a process utilizing sodium hydride (NaH) to couple hydroxyethyl adenine with diethyl p-toluenesulfonyloxymethanephosphonate. The use of NaH presented safety and consistency problems. It was found that sodium tert-butoxide (NaOtBu) was a suitable replacement for NaH as the base to effect the coupling reaction. Optimization of reagent stoichiometry and introduction of a simplified filtration workup procedure led to a robust process affording diethyl-PMEA in consistent yields and purities. The modifications and process improvements were scaled-up successfully to batch sizes of >100 kg.