Preparative-scale Enzyme-catalyzed Synthesis of (R)-α-Fluorophenylacetic Acid

A preparative-scale asymmetric synthesis of (R)-α-fluorophenylacetic acid, a useful chiral derivatizing reagent, is described. Starting from ethyl α-bromophenylacetate, α-fluorophenylmalonic acid dipotassium salt was prepared in three steps (54% yield), including nucleophilic substitution by the fluoride ion as the keystep. Both the purified form and crude preparation of arylmalonate decarboxylase in E. coli worked well on this substrate, and (R)-α-flurophenylacetic acid (>99% e.e.) was prepared in a quantitative yield.