Halogen dealkylation

Halogen dealkylation mimics O-dealkylation both in terms of mechanism and the commonality of the process. Virtually any drug that contains a carbon-hydrogen bond adjacent to a halogen atom will be subject to P450-catalyzed oxidative dehalogenation (Fig. 4.61). 

A broad spectrum of chemical reactions can be catalyzed by enzymes Hydrolysis, esterification, isomerization, addition and elimination, alkylation and dealkylation, halogenation and dehalogenation, and oxidation and reduction. The last reactions are catalyzed by redox enzymes, which are classified as oxidoreductases and divided into four categories according to the oxidant they utilize and the reactions they catalyze 1) dehydrogenases (reductases), 2) oxidases, 3) oxygenases (mono- and dioxygenases), and 4) peroxidases. The latter enzymes have received extensive attention in the last years as bio catalysts for synthetic applications. Peroxidases catalyze the oxidation of aromatic compounds, oxidation of heteroatom compounds, epoxidation, and the enantio-selective reduction of racemic hydroperoxides. In this article, a short overview... 

Thus, exposure to any of these enzyme inducers concurrent with or after exposure to diazinon may result in accelerated bioactivation to the more potent anticholinesterase diazoxon. The extent of toxicity mediated by this phenomenon is dependent on how fast diazoxon is hydrolyzed to less toxic metabolites, a process that is also accelerated by the enzyme induction. Similarly, concurrent exposure to diazinon and MFO enzyme-inhibiting substances (e.g., carbon monoxide ethylisocyanide SKF 525A, halogenated alkanes, such as CC14 alkenes, such as vinyl chloride and allelic and acetylenic derivatives) may increase the toxicity of diazinon by decreasing the rate of the hydrolytic dealkylation and hydrolysis of both parent diazinon and activated diazinon (diazoxon) (Williams and Burson 1985). The balance between activation and detoxification determines the biological significance of these chemical interactions with diazinon. 

DDT p,p -dichloro-diphenyl-trichloroethane. deacetylation removal of acetyl group, dealkylation removal of alkyl group, deaminate removal of amine group, dechlorination removal of chlorine group, de-ethylation removal of ethyl group, dehalogenation removal of halogen atom(s). 

The 3-mercapto-1,2-dithiolium salts (39a) also suffer deprotonation on addition of water. This behavior is the basis of a simple and effective method of purification, which is particularly useful for aryl-substituted trithiones. 48 The tendency towards charge neutralization in the alkylmercapto-1,2-dithiolium ions is also the reason for the relative ease of removal of the alkyl group (cf. thermal dealkylation, transmethylation), as well as for the extremely labile bonding of other groups such as acyl—, —S02—, —SO—, —S2C1, and halogen to the exocyclic S atom of the corresponding 3-mercapto-1,2-dithiolium derivatives. 

When X = 0 or S in reaction 4 (Fig. 13.3), the metabolic reactions are known as 0-deal-kylations or S-dealkylations, respectively. O-demethylation is a typical case of the former reaction. And when X = halogen in reactions... 

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