D-Idose, represented in its open-chain form as (2R,3R,4S,5R)-2,3,4,5,6-Pentahydroxyhexanal, is a rare aldohexose primarily used as a specialty reagent in biochemical and medicinal chemistry research. It functions as a key chiral building block in the synthesis of complex carbohydrates, including glycosides, oligosaccharides, and glycosaminoglycans such as heparin and dermatan sulfate via conversion to iduronic acid derivatives. Its distinctive stereochemistry and conformational flexibility make it valuable for studying carbohydrate structures, metabolic pathways, and asymmetric synthesis of enantiopure compounds in pharmaceutical development. Due to its scarcity and specialized applications, it is not commonly used in commercial food or cosmetic products.