Iodine biological importance

In Quest of Friendly Free Radicals Reactions of Iodine Atom Free Radicals with Some Biologically Important Compounds... 

A novel hypervalent iodine-induced direct intramolecular cyclization of a-(aryl)alkyl-jS-dicarbonyl compounds 33 has been recently reported (Scheme 15) [30]. Both meta- and para-substituted phenol ether derivatives containing acyclic or cyclic 1,3-dicarbonyl moieties at the side chain undergo this reaction in a facile manner affording spirobenzannulated compounds 34 that are of biological importance. 

The number of elements that are known to be biologically important comprises a relatively small fraction of the 109 known elements. Natural abundance limits the availability of the elements for such use. Molybdenum (Z = 42) is the heaviest metal, and iodine (Z = 53) is the heaviest nonmetal of known biological importance. The metals of importance in enzymes are principally those of the first transition series, and the other elements of importance are relatively light sodium, potassium, magnesium, calcium, carbon, nitrogen, phosphorus, oxygen, chlorine, and, of course, hydrogen. 

Since iodine in these processes is present in various chemical forms, the chemical speciation of iodine is important for understanding its geochemistry in oceans. Further, iodine is redox sensitive and the most abundant biophilic minor element in the oceans. Here, the behaviors of various iodine species in seawater will be described in regard to biological and abiological processes. 

Iodine is essential for the normal development of all animals and man. Its basic biological importance is indicated by the fact that the tadpole will not undergo metamorphosis into the frog without the function of the thyroid gland in secreting the iodine-containing thyroid hormones. 

Abstract Free radicals are generally considered as villain. Thns the image of free radicals emerges as a dangerons entity which is perhaps always injnrions to health. One conld, however, ask if there is any beneficial effect of free radicals. A series of studies has been embarked npon this idea in quest of friendly free radicals in this concept the possible nse of iodine free radicals was explored initially throngh their reaction with varions biologically important componnds inclnding components of DNA/RNA/PROTEIN. 

The hypervalent iodine-induced direct intramolecular cyclization of a-(aryl)alkyl-p-dicarbonyl derivatives 305 affords biologically important spirobenzannulated compounds 306 (Scheme 3.125) [366]. 

Chlorpromazine plus iodine is not a combination that is likely to occur in a pharmaceutical formulation nor is the interaction of any significance in therapeutics. The study of the reaction is of biological importance, however, because of the information provided with respect to the electronic properties of the phenothiazine derivatives, and these properties in turn are likely to have significance in understanding the underlying mechanisms of the drug. That is, CPZ-I2 is a model system. 

The major biologically important molecules are formed primarily from 0 gen, carbon, hydrogen, and nitrogen. Some elements found in the body are crucial for life, although they are present in very tiny amounts (trace elements). Some of these trace elements include chromium, copper, fluorine, iodine, and selenium. 

Another source of hypervalent iodine for quinoxaline synthesis was found in (diacetoxyiodo)benzene [125]. 10 mol% of the catalyst was found to be enough to catalyze the one-pot reaction between 1,2-diaminobenzenes and internal alkynes generating biologically important quinoxaline derivatives (Scheme 89). 

A notable utility of iodine (ID) reagent, FIFA was demonstrated in the one-pot synthesis of biologically important framework, 3-hydroxyquinolin-2(lH)-ones 117. In this reaction, FIFA effectively converted the readily available N-phenylacetoacetamides 115 into their a-hydroxylated intermediates 116. Treatment of 116 with concentrated sulfuric acid xmderwent dehydrative cyclization to afford 3-hydroxyquinolin-2(lH)-ones in moderate-to-excellent yields. This new strategy allowed to prepare viridicatin 118, a natural product endowed with potent anti-HIV activity (Scheme 25) [41]. 

Zhao et al. utilized the remarkable oxidative property of FIFA in a C-C bond formation to prepare an array of 3-arylquinolin-2-ones 120 (Scheme 26). FIFA-promoted oxidation of N-methyl-N-phenylcinnamamides 119 in the presence of a Lewis acid afforded 3-arylquinolin-2-ones in good yields. Formation of 3-arylquinolin-2-ones was realized through the FIFA-promoted simultaneous C-C bond formation and 1,2-aryl migration. This simple and metal-free FIFA-mediated green approach for the biologically important 3-arylquinolin-2-ones also widen the synthetic utility of hypervalent iodine reagents [42]. 

Biologically important compounds, e.g., compounds of fluorine and iodine, biogenic amines, some antioxidants or plasticizers (e.g. phthalates). 

As mentioned earlier, metal complexation not only allows isolation of the QM derivatives but can also dramatically modify their reactivity patterns.29o-QMs are important intermediates in numerous synthetic and biological processes, in which the exocyclic carbon exhibits an electrophilic character.30-33 In contrast, a metal-stabilized o-QM can react as a base or nucleophile (Scheme 3.16).29 For instance, protonation of the Ir-T 4-QM complex 24 by one equivalent of HBF4 gave the initial oxo-dienyl complex 25, while in the presence of an excess of acid the dicationic complex 26 was obtained. Reaction of 24 with I2 led to the formation of new oxo-dienyl complex 27, instead of the expected oxidation of the complex and elimination of the free o-QM. Such reactivity of the exocyclic methylene group can be compared with the reactivity of electron-rich enol acetates or enol silyl ethers, which undergo electrophilic iodination.34... 

Iodine and iodine derivatives are ubiquitous in nature and a report describing the determination of iodine in environmental and biological samples has been published [197]. Electrochemical techniques are important, in particular, for inorganic iodine species in aqueous media. The direct detection of iodine by differential pulse and stripping voltammetry has been reported... 

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