Methyl vitamin

Transfer of a methyl group from methyl vitamin B12 to Hg(II), Tl(III), Pt(II), and Au(I) was found to occur (334). An acid-base reaction path was proposed for mercury and thallium, whereas an oxidation-reduction sequence involving Pt(IV) and Au(lII) intermediates was suggested. 

Apples Diphenylamine (DPA), Thiabendazole, and Azinphos Methyl Vitamins A, C, Potassium Oranges, Bananas, Kiwis, Watermelon, Tangerines... 

Microorganisms can transfer methyl groups to various heavy metals and metalloids (e.g., Se, As), which results in mobilizing these heavy metals and promoting their potentiation as environmental toxicants. Such methylation is attributed to the enzymatic system involved in the anaerobic generation of methane, where the methyl donor is methylcobal-amin (methyl vitamin B12). This is exemplified by the case of mercury (see Figure 9.12). 

The possible relationship of the methane fermentation with the more conventional examples of one-carbon metabolism as catalyzed by folate and vitamin B12 cofactors has been long apparent. 5-Methyl tetrahydro-folate, 5,10-methylene tetrahydrofolate, and methyl vitamin B12 are converted to methane by cell-free extracts of M. barkeri 32) and M. omeli-anskii (33). The involvement of vitamin B12 is further implicated by its high cellular level in methane bacteria and by the isolation of B12-containing proteins in extracts of M. barkeri 30) which stimulate methane evolution from methyl vitamin B12. The components and pathways that can be demonstrated in cell-free M. barkeri extracts 32) are listed below. 

Reduction of A, lV10-Methylene-FH4 A -Methyl Vitamin Methyl-B12... 

Naphthoquinone, 2-hydroxy-3-methyl-vitamin K1 inhibits incorporation of glucosamine. 

CAS 58-27-5 EINECS/ELINCS 200-372-6 Synonyms Menadion Menaphthon 2-Methyl-1,4-naphthalenedione 2-Methyl-1,4-naphthoquinone 1,4-Naphthalenedione, 2-methyl-Vitamin K3... 

Many C. in the wider sense are synthesized from vitamins. The relationships of some C. to vitamins and metabolic function are listed in the table. Strictly speaking, ATP, which commands a special position in metabolism, does not fit the definition of a CThe C. of C -unit transfer are S-Adenosylmethionine (see), Tetrahydrofolic acid (see) and Biotin (see). The C. of C2"transfer are Coenzyme A (see) and Thiamin pyrophosphate (see). Vitamin B[j is involved in various metabolic reactions, in free form, as methyl-vitamin B,2 and as S -Deoxyadenosylcobalamine (see). 

Vitamin B12 and folate are involved in the synthesis of methionine from homocysteine in the presence of methionine synthase for which 5-methyl tetrahydrofolate (THF) and methyl-vitamin B12 are cofactors. Methionine in turn along with adenosine triphosphate (ATP) forms 5 -adenosyl methionine (SAM), which is the only methyl group donor in the human central nervous system (CNS). SAM donates methyl groups in number of methylation reactions, involving synthesis of myelin, phospholipids, proteins and neurotransmitters (catecholamine and indoleamines). The methylation cycle is also of importance for the generation of active folate forms. When the methyl group is transferred, SAM is converted to S -adenosyl homocysteine (SAH) which is subsequently converted to homocysteine and adenosine. Hence, homocysteine, vitamin B12 and folate are linked together in one carbon cycle (Moretti et al. 2008). 

The order of ligands for the kinetic rmn -effect in Co" corrinoids parallels that for the thermodynamic /ran -effect, and it has been demonstrated that, in the binding of corrinoids to proteins and polypeptides, the formation of hydrogen-bonds is far more important than coordination by the metal atom. Methyl vitamin B is capable of transferring... 

For the reaction with methyl cobalamin (methyl vitamin B12), see From Lead(ll) and Lead(IV) Compounds and CH3I or Other Methylating Agents , p. 71. 

It is important in the body as, except for methionine, it is the only substance known to take part in methylating reactions. Sometimes regarded as a member of the vitamin B group. 

Vitamin Bj 2 is concerned in the biosynthesis of methyl groups of choline and methionine. 

Several substances having vitamin K. activity have been isolated from natural sources. Vitamin Ki from alfalfa oil, is 2-methyl-3-phytyl-1,4-naphthoquinone. 

The term vitamin K2 was applied to 2-methyl-3-difarnesyl-l,4-naphthoquinone, m.p. 54 C, isolated from putrefied fish meal. It now includes a group of related natural compounds ( menaquinones ), differing in the number of isoprene units in the side chain and in their degree of unsaturation. These quinones also appear to be involved in the electron transport chain and oxidative phosphorylation. 

As noted by Robinson and Strachan (1), after considerable activity in the period 1885 to 1895 thiazolecarboxylic acids received little attention until 1935. Isolation of 4-methyl-5-thiazolecarboxylic acid after degradation of vitamin Bj gave new interest to the chemistry of these compounds. 

The structure of vitamin D2 is the same as that of vitamin D3 except that vitamin D2 has a double bond between C 22 and C 23 and a methyl substituent at C 24... 

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

X5lenol is an important starting material for insecticides, xylenol—formaldehyde resins, disinfectants, wood preservatives, and for synthesis of a-tocopherol (vitamin E) (258) and i7/-a-tocopherol acetate (USP 34-50/kg, October 1994). The Bayer insecticide Methiocarb is manufactured by reaction of 3,5-x5lenol with methylsulfenyl chloride to yield 4-methylmercapto-3,5-xylenol, followed by reaction with methyl isocyanate (257). Disinfectants and preservatives are produced by chlorination to 4-chloro- and 2,4-dich1oro-3,5-dimethylpheno1 (251). 

Methyl vinyl ketone is used as a comonomer in photodegradable plastics, and is an intermediate in the synthesis of steroids and vitamin A. It is highly toxic and faciUties handling over a threshold of 100 lbs (45.5 kg) are subject to special OSHA documentation regulations (273). 

Derivatives of ubiquiaones are antioxidants for foodstuffs and vitamins (qv) (217,218). Ubichromenol phosphates show antiinflammatory activity (219). Chroman o1 compounds inhibit oxidation of fats and can be used ia treatment of macrocytic anemias (220). Monosulfate salts of 2,3-dimethoxy-5-methyl-6-substitutedhydroquiaone have been reported to be inhibitors of Hpid oxidation ia rats (221). Polymers based on chloranilic and bromanilic acid have been prepared and contain oxygenated quiaones (63), which are derived from 1,2,3,4-benzenetetrol (222). 

Ethers of benzenepentol have been obtained by Dakin oxidation of the appropriately substituted acetophenone. Thus, the oxidation of 2-hydroxy-3,4,6-ttimethoxyacetophenone and 2-hydroxy-3,4,5-ttimethoxyacetophenone with hydrogen peroxide ia the presence of alkali gives l,2-dihydroxy-3,4,6-ttimethoxybenzene and l,2-dihydroxy-3,4,5-ttimethoxybenzene, respectively further methylation of these ethers yields the pentamethyl ether of benzenepentol (mp 58—59 degC) (253). The one-step aromatization of myoinositol to produce esters of pentahydroxybenzene is achieved by treatment with carboxylic acid anhydrides ia DMSO and ia the presence of pyridine (254) (see Vitamins). 6-Alkyl- or... 

Thiamine [59-43-8] is the official lUPAC-IUB name for 3-(4-aniiQO-2-methyl-5pyrimidiQyl) methyl-5-(-2-hydroxyethyl)-4-methylthia2olium chloride, C 2H yN40SCl (1). The names thiamine, thiamin (used in many official and commercial documents), aneurine, and the older term vitamin are also casually used. These names usually refer to the chloride hydrochloride [67-03-8] (2), the common biological and commercial form. 

Vitamin A palmitate [79-81-2] (3), a commercially important form of the vitamin, is produced from vitamin A acetate (2) via a transesterification reaction with methyl palmitate. En2ymatic preparation of the palmitate from the acetate has also been described (22). 

Metabolism and Mobilization. On entry of vitamin B 2 into the cell, considerable metaboHsm of the vitamin takes place. Co(III)cobalamin is reduced to Co(I)cobalamin, which is either methylated to form methylcobalamin or converted to adenosylcobalamin (coenzyme B>22)- The methylation requires methyl tetrahydrofolate. 

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