The molecule is an iminium betaine resulting from a transfer of a proton from the carboxy group to the imino group of 5-hydroxyectoine. It is the major microspecies at pH 7.3 (according to Marvin v 6.2.0.). It is a tautomer of a 5-hydroxyectoine.
(4S,5S)-5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidin-3-ium-4-carboxylate