Enantioselective synthesis of 5-fluoro-L-DOPA via chemoenzymatic route

The title compound, 5-fluoro-3,4-dihydroxy-l-phenylalanine, was prepared in four steps, with the key step having been the enantiospecific production of 5-fluoro-l-tyrosine by the chemoenzymatic reaction between 2-fluorophenol, potassium pyruvate and ammonia promoted by the live culture of Citrobacter freundii cells. 5-Fluoro-l-tyrosine was hydroxylated by sequential nitration, reduction and diazotization followed by hydrolysis.