This question involves identifying the correct structural features of a disaccharide. The image shows a disaccharide structure where we need to determine the type of sugar rings (pyranose or furanose) and the nature of the glycosidic linkage (α or β).

Key Concepts:

• Pyranose ring: A 6-membered sugar ring (5 carbon atoms + 1 oxygen atom).
• Furanose ring: A 5-membered sugar ring (4 carbon atoms + 1 oxygen atom).
• Glycosidic linkage: The bond connecting two monosaccharide units. Its configuration (α or β) depends on the orientation of the anomeric carbon's hydroxyl group relative to the ring.
• For α-linkage: The -OH group on the anomeric carbon is axial (downwards in Haworth projection).
• For β-linkage: The -OH group on the anomeric carbon is equatorial (upwards in Haworth projection).

Step-by-Step Analysis:

Step 1: Identify ring sizes. Count the atoms in each ring:

• Ring (a) has 6 atoms (5C + 1O) → pyranose ring.
• Ring (b) has 5 atoms (4C + 1O) → furanose ring.

Step 2: Determine the glycosidic linkage. Look at the anomeric carbon (C1) involved in the linkage:

• The linkage is between C1 of ring (a) and the oxygen of ring (b).
• In standard Haworth projection, if the glycosidic bond is pointing downward from the anomeric carbon, it is α-linkage; if upward, it is β-linkage.
• In the given structure, the glycosidic bond from ring (a) is downward → α-linkage.

Therefore, ring (a) is pyranose with α-glycosidic link, which matches the first option.

Related Topics:

• Carbohydrates: Monosaccharides and disaccharides.
• Haworth projections and chair conformations.
• Anomeric carbon and its stereochemistry.

Important Formulae/Theory:

• Pyranose ring: 6-membered (C₅O).
• Furanose ring: 5-membered (C₄O).
• α-glycosidic link: -OH group axial (down).
• β-glycosidic link: -OH group equatorial (up).