Lobry de Bruyn-Alberda van Ekenstein transformation

What is Lobry de Bruyn-Alberda van Ekenstein transformation?

The Lobry de Bruyn-Alberda van Ekenstein reaction, discovered in 1895, involves the reciprocal conversion of carbohydrates to their isomers in an alkaline solution, with the help of an enediolic intermediate. The reaction is named after its discoverers, and is also known by other names such as the Lobry de Bruyn-Alberda van Ekenstein transformation, Lobry de Bruyn-Alberda van Ekenstein rearrangement, Lobry de Bruyn-Albreda van Ekenstein C-2 epimerization, and Lobry de Bruyn-van Ekenstein transformation. This glycochemical reaction is catalyzed by hydroxide, and is independent of counterions, relying only on the concentration of the base and temperature.

Lobry de Bruyn-Alberda van Ekenstein transformation - general reaction scheme - Lobry de Bruyn-Alberda van Ekenstein rearrangement - Lobry de Bruyn-Albreda van Ekenstein  C-2 epimerization - Lobry de Bruyn-van Ekenstein transformation
Lobry de Bruyn-Alberda van Ekenstein transformation

The reaction occurs between glucose, mannose, and fructose, irrespective of the base used, such as KOH, NaOH, NH4OH, Mg(OH)2, Na2CO3, or K2CO3. Similarly, galactose forms an equilibrium with tagatose and talose. Interestingly, sorbose does not undergo this transformation, and glucose treated with lead hydroxide yields only mannose, while fructose does not produce either of its corresponding aldose isomers.

It has been found that this base-catalyzed interconversion of carbohydrates is essentially similar to the isomerase-catalyzed group transfer reaction of glucose-6-phosphate. Additionally, carbohydrates may undergo retro-aldol condensation and degrade into lower analogs under basic conditions.

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