Question

Disaccharides are joined by glycosidic bonds formed between the anomeric carbon on one monosaccharide and a hydroxyl ( − OH ) group of another monosaccharide. Identify the types of linkages in each of the three disaccharides. Only place three of the linkages.

Answer 1

Solution and Explanation

1. OH group is present above the plane in monosaccharide 1. Carbon atoms in both the rings are numbered in such way that carbon behind the oxygen at the right hand is C1 in the both rings. Carbon 1 bonds to carbon 2 of the next monosaccharide. Hence, the glycosidic linkage between disaccharide is  $\beta 1 \rightarrow 2$ .

2. OH group is present above the plane in monosaccharide 1 while in ring 2 it is present below the plane. Carbon atoms in both the rings are numbered in such way that carbon behind the oxygen at the right hand is C1 in the both rings. Carbon 2 bonds to carbon 1 of the next monosaccharide. Hence, the glycosidic linkage between disaccharide is   $\beta 2 \rightarrow \alpha 1$.

3. OH group is present below the plane in below the plane in both the rings. Carbon atoms in both the rings are numbered in such way that carbon behind the oxygen at the right hand is C1 in the both rings. Carbon 1 bonds to carbon 4 of the next monosaccharide. Hence, the glycosidic linkage between disaccharide is $\alpha 1 \rightarrow 4$.