betaDribofuranose

Beta-D-ribofuranose is the beta anomer of D-ribose in its five-membered ring form (furanose). Its molecular formula is C5H10O5. In solution, ribose exists mainly as furanose rings and can interconvert between different stereochemical forms; the beta anomer is the form commonly associated with RNA nucleotides.

The beta designation refers to the configuration at the anomeric carbon (C1') of the sugar ring. In the standard Haworth projection, the hydroxyl group at C1' in the beta form is on the same side as the exocyclic CH2OH group. This contrasts with the alpha anomer, where the C1' hydroxyl has the opposite orientation.

Biological role: Beta-D-ribofuranose is a key component of all ribonucleosides, namely adenosine, cytidine, guanosine, and uridine. When linked to phosphate groups, these nucleosides form ribonucleotides, which constitute RNA and participate in cellular energy transfer and metabolism. The ribose unit is produced and recycled in cells via pathways that supply ribose-5-phosphate and nucleotide biosynthesis.

Relation to DNA: In DNA, the sugar is beta-D-2'-deoxyribofuranose, which lacks the 2'-hydroxyl group compared to ribose. This structural difference underpins many biochemical and structural distinctions between RNA and DNA.

Physical properties: In aqueous solution, the furanose ring is flexible and can adopt multiple conformations; the open-chain form exists only in trace amounts. Beta-D-ribofuranose thus represents the dominant cyclic form of ribose in biological contexts.