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A reaction involved in the metabolism of sugars is the
Chapter 16, Problem 79SP(choose chapter or problem)
A reaction involved in the metabolism of sugars is the splitting of fructose-1,6-diphosphate to give glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. In the living system, this retro-aldol is catalyzed by an enzyme called aldolase; however, it can also be catalyzed by a mild base. Propose a mechanism for the base-catalyzed reaction.
Questions & Answers
QUESTION:
A reaction involved in the metabolism of sugars is the splitting of fructose-1,6-diphosphate to give glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. In the living system, this retro-aldol is catalyzed by an enzyme called aldolase; however, it can also be catalyzed by a mild base. Propose a mechanism for the base-catalyzed reaction.
ANSWER:
Solution:
Here we have to propose a mechanism of the base catalysed reaction for the formation of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate from fructose-1,6-diphosphate.
Retro aldol reaction is the reverse of an aldol addition, in which a beta-hydroxy ketone fragments to form a carbonyl compound and the enolate of an alpha-acidic carbonyl compound.
Step 1
Preparation of glyceraldehyde-3-phosphate from fructose-1,6-diphosphate :-
In this reaction, fructose-1,6-diphosphate in presence of a base release one molecule of water and forms an intermediate. This intermediate undergoes rearrangement and splitting of the intermediate leads the formation of glyceraldehyde-3-phosphate along with a resonance stabilized carbanion ion.
(fructose-1,6-diphosphate) (Intermediate) (glyceraldehyde-3-phosphate)