The molecule is a dipeptide zwitterion obtained by transfer of a proton from the carboxy to the amino terminus of His-Pro. Major species at pH 7.3. It is a tautomer of a His-Pro.
(2S)-1-[(2S)-2-azaniumyl-3-(1H-imidazol-5-yl)propanoyl]pyrrolidine-2-carboxylate