Question

Which of the following is/are non-reducing sugars?

• A. Methyl $\alpha$-D-(+)-glucopyranose
• B. Methyl $\beta$-D-(+)-glucopyranose
• C. Glucose pentaacetate
• D. $\alpha$-D-(+)-glucopyranose

Answer 1

Answer: (A), (B)

Methyl $\beta$-D-(+)-glucopyranose
Methyl $\alpha$-D-(+)-glucopyranose

Glucose pentaacetate and $\alpha$- or $\beta$-D-(+)-glucopyranose are reducing sugars as the aldehyde group is either free or present in the form of hemiacetal.
Methyl $\alpha$- or $\beta$-D-(+)-glucopyranose are non-reducing sugars as the aldehyde group is not free, being present in the form of acetal.