The synthesis of (2R,3S)-3,4,4,4-tetrafluorovaline, a fluorinated derivative of the canonical alpha-amino acid l-valine, is reported for the first time. A highly enantio- and diastereoselective direct catalytic asymmetric Mannich-type reaction was applied as the key C-C bond-forming step to afford gram quantities of a central synthetic intermediate. The conformation of the novel fluorinated alpha-amino acid was analyzed by X-ray crystallography, NMR spectroscopy, and computational methods, which, together with its calculated and experimental physicochemical properties, indicated that the fluorinated valine is a bioisostere of l-isoleucine.