Chemistry - Biomolecules Question with Solution | TestHub

To determine D or L configuration, the main carbon chain must be vertical with the most oxidized carbon (CHO) at the top and the terminal –CH₂OH group at the bottom.

In structure (B), the lowest chiral carbon has –CH₂OH on the right and –OH at the bottom.

Rotating or swapping these groups to correctly place –CH₂OH at the bottom puts the –OH group on the left side.

Since the –OH group on the highest-numbered chiral center is on the left, it represents an L-sugar. Therefore, structure (B) is not a D-sugar.