The molecule is a disaccharide that is D-mannitol in which the hydroxy group at position 2 has been converted into its alpha-D-galactopyranoside It derives from a D-mannitol.
(2R,3R,4S,5R)-5-[(2R,3R,4S,5R,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxyhexane-1,2,3,4,6-pentol