Question

Draw the structures of the compound ethyl β-D-ribofuranoside.Allose is the C3 epimer of glucose, and ribose is the C2 epimer of arabinose.

Accepted Answer

Understand the problem: The task is to draw the structure of ethyl β-D-ribofuranoside. This involves understanding the structure of ribose, its furanose form, and the β-glycosidic bond with an ethyl group. Additionally, the problem mentions epimers, which are sugars that differ in configuration at a single stereogenic center. Step 1: Recall the structure of D-ribose. D-ribose is a five-carbon aldose sugar (an aldopentose) with the molecular formula C₅H₁₀O₅. In its Fischer projection, the hydroxyl groups on carbons 2, 3, and 4 are arranged as follows: OH on the right (C2), OH on the right (C3), and OH on the right (C4). Step 2: Convert D-ribose into its furanose form. In aqueous solution, D-ribose cyclizes to form a five-membered ring (furanose) by the reaction of the hydroxyl group on C4 with the aldehyde group on C1. This forms a hemiacetal. The β-anomer is formed when the hydroxyl group on C1 is oriented above the plane of the ring in the Haworth projection. Step 3: Add the ethyl group to form ethyl β-D-ribofuranoside. The ethyl group replaces the hydrogen of the hydroxyl group on C1, forming a glycosidic bond. This results in the structure of ethyl β-D-ribofuranoside, where the ethyl group is attached to the anomeric carbon (C1) and the β-configuration is maintained. Step 4: Verify the stereochemistry and draw the final structure. Ensure that the stereochemistry of the hydroxyl groups on C2, C3, and C4 matches that of D-ribose in the furanose form. The β-glycosidic bond should have the ethyl group pointing above the plane of the ring in the Haworth projection.

Draw the structures of the compound ethyl β-D-ribofuranoside.
Allose is the C3 epimer of glucose, and ribose is the C2 epimer of arabinose.

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Key Concepts

Furanose Structure

Epimerization

Glycosidic Bond Formation