(2S,4R)-4-Fluoro-pyrrolidinium-2-carboxyl-ate.

The crystal structure of the title compound, C(5)H(8)FNO(2), at 100 K, displays inter-molecular N-H⋯O hydrogen bonding between the ammonium and carboxyl-ate groups as a result of its zwitterionic nature in the solid state. The five-membered ring adopts an envelope conformation with the C atom at the 3-position as the flap. The compound is of inter-est with respect to the synthesis and structural properties of synthetic collagens. The absolute structure was determined by comparison with the commercially available material.