Question

Deduce the structure of the disaccharide maltose from the following data.

[1]Hydrolysis yields D-glucose exclusively.

[2] Isomaltose is cleaved with -$\mathbf{\alpha }$glycosidase enzymes.

[3] Isomaltose is a reducing sugar.

[4]Methylation with excess ${\mathbf{CH}}_{\mathbf{3}}\mathbf{I}\mathbf{,}\mathbf{}{\mathbf{Ag}}_{\mathbf{2}}\mathbf{O}$and then hydrolysis with${\mathbf{H}}_{\mathbf{3}}{\mathbf{O}}^{\mathbf{+}}$ forms two products:

(Both anomers are present.)

Short answer

Answer

Step-by-step solution

Disaccharide

When subjected to hydrolysis in the presence of acids or bases, the carbohydrate generates two monosaccharide molecules termed disaccharides.Sucrose is a vital disaccharide that generates D-(+)-glucose and D-(-) fructose on hydrolysis.

Maltose

The disaccharide created from two $\mathbf{\alpha }$ -D glucose units is termed maltose. The two glucose units are connected via $\mathbf{\alpha }$-1, 4 glycosidic bond. Maltose comes under the category of reducing sugars.

Structure of the disaccharide isomaltose

• Hydrolysis yields D-glucose exclusively. Hence, the disaccharide is generated from two glucose units.
• Isomaltose is cleaved with$\mathrm{\alpha }$-glycosidase enzymes. Thus the glycosidic linkage is present between the two glucose units.
• Isomaltose is a reducing sugar. So, the disaccharide comprises a hemiacetal and undergoes mutarotation.

The structure of the disaccharide isomaltose, and the reaction is given as:

Structure of disaccharide isomaltose

Reaction leading to the disaccharide maltose