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Title: Demethylation  
Author: World Heritage Encyclopedia
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Subject: Methylation, FTO gene, Tert-Butylthiol, Methiopropamine, Methylone
Collection: Gene Expression, Organic Reactions
Publisher: World Heritage Encyclopedia


Demethylation is the chemical process resulting in the removal of a methyl group (CH3) from a molecule.[1][3] A common way of demethylation is the replacement of a methyl group by a hydrogen atom, resulting in a net loss of one carbon and two hydrogen atoms.

The counterpart of demethylation is methylation.


  • In biochemistry 1
  • In Organic chemistry 2
    • O-Desmethylation 2.1
  • History 3
    • N-Demethylation 3.1
  • References 4
  • See also 5

In biochemistry

In biochemical systems, the process of demethylation is catalyzed by demethylases. These enzymes oxidize N-methyl groups, which occur in histones and some forms of DNA.

R2N-CH3 + O → R2N-H + CH2O

One such oxidative enzyme family is the cytochrome P450[6] Alpha-ketoglutarate-dependent nonheme enzymes are active for demethylation of DNA, operating by similar pathway.

In Organic chemistry


Desmethylation, typically refers to cleavage of ethers, especially aryl ethers, although there is some exceptions, for instance cf. "desipramine".

Apparently, aryl ethers are pervasive in lignin-derived compounds.nav_box_header

The reaction typically requires harsh conditions or harsh reagents. For example, the methyl ether in

See also

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N-demethylation of 3° amines, is by the Von Braun reaction, which uses BrCN as the reagent to give the corresponding nor derivatives. The etymological meaning of the word nor is ″N ohne R″. A modern variation of the Von Braun rxn has been developed where BrCN has been superseded by ethyl chloroformate, respectively. Paxil prepared from arecoline is a good example of where this rxn has been applied, as well as GSK-372,475, for example.


Methyl esters also are susceptible to demethylation, which is usually achieved by saponification. Highly specialized demethylations are abundant such as the Krapcho decarboxylation:

ROR + BBr3 → RO+(BBr3)R
RO+(BBr3)R → ROBBr2 + RBr
ROBBr2 + 3 H2O → ROH + B(OH)3 + 2 HBr

hydrolysis to give the alcohol or phenol, boric acid, and hydrogen bromide as products.[14]


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