Synthesis and physicochemical evaluation of tetrafluorinated GABA analogue

Synthesis of 2,2,3,3-tetraftluoro-γ-aminobutyric acid (tetraF-GABA) starting from commercially available 2,2,3,3-tetrafluorobutane-1,4-diol is described. The straightforward nine-step reaction sequence allowed the production of up to 20 g of the target amino acid in 41 % overall yield. Potentiometric titration revealed increased acidity of both ionizable moieties in the title compound (the pK_a values were diminished by 1.6 and 4.0 units for the COOH and NH₃⁺ groups, respectively, as compared to parent GABA). X-ray diffraction studies and DFT calculations demonstrated different preferential conformations in solid state and solution, although the fluorine gauche effect was observed in both cases.