The molecule is a mannarate(2-) that is the dianion obtained by the deprotonation of the carboxy groups of D-mannaric acid. It is a conjugate base of a D-mannarate(1-). It is an enantiomer of a L-mannarate(2-).
(2S,3S,4S,5S)-2,3,4,5-tetrahydroxyhexanedioate