The molecule is a D-galacturonic acid having a 4-deoxy-alpha-L-threo-hex-4-enopyranosyluronic acid moiety attached at the 4-position. It is a conjugate acid of a 4-(4-deoxy-beta-D-gluc-4-enosyluronate)-D-galacturonate(2-).
(2R,3R,4S)-2-[(2S,3R,4R,5R)-2-carboxy-4,5,6-trihydroxyoxan-3-yl]oxy-3,4-dihydroxy-3,4-dihydro-2H-pyran-6-carboxylic acid