7-Fluoro-DL-tryptophan (la), 4,7-difluoro-DL-tryptophan (1 b) and 5,7 difluoro-DL-tryptophan (lc) were prepared by Fischer indole cyclization. The resolution was achieved by treatment of the N-trifluoroacetyl derivatives with carboxypeptidase A. All 7-fluorotryptophans are slow substrates for tryptophan indole-lyase from E. coli. Fluorinated analogues of amino acids are useful to study amino acid reactions and metabolism.2 Recently, there has been an increasing interest in the incorporation of fluoroamino acids in large biomolecules.3 F-Phe-, F-Trp-, and F-Tyr-labeled proteins have been used in 19F NMR studies to characterize fuctionally significant conformational changes.4 Among fluorotryptophans, 4-, 5- and 6-fluorotryptophan are commercially available, and used extensively.2cp3h.5 4, 5, 6, 7-Tetrafluorotryptophan was synthesized and tested for enzyme inhibition .6 However, there is only one report for preparation of la and lc, which were not resolved,he and the preparation of 1 b has not been previously reported. We report here the synthesis of 7-fluorotryptophans la-c, their resolution, and their reactions with tryptophan indole-lyase (tryptophanase) from E. coli.