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GATE 2024 CY – Question 41

Organic Chemistry · Biomolecules: Structure, properties and reactions of mono- and di-saccharides, physicochemical properties of amino acids, chemical synthesis of peptides, chemical structure determination of peptides and proteins, structural features of proteins, nucleic acids, lipids, steroids, terpenoids, carotenoids, and alkaloids. · 2 marks · Multiple choice

Fischer presentation of D-(-)-fructose is given below. The correct structure of α-L-(+)-fructofuranose is

Fischer projection of D-fructose and four fructofuranose structures.
  1. Option A in the figure
  2. Option B in the figure
  3. Option C in the figure
  4. Option D in the figure

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Show answer and explanation

Correct answer: (A) Option A in the figure

Explanation

Invert the Fischer stereocentres of D-fructose to obtain L-fructose, then form the C2–O5 furanose ring. Choose the alpha anomer with the appropriate relationship between the anomeric hydroxyl and the reference substituent. The complete configuration shown in A is the official answer; C has the wrong stereochemical assignment.

Official GATE 2024 answer key: https://gate2026.iitg.ac.in/doc/download/2024/CYFinalAnswerKey.pdf