Synthesis and DABCO-induced demethylation of 3-cyano-4-methoxy-2-pyridone derivatives

An efficient method for synthesis and demethylation of 3-cyano-4-methoxy-2-pyridone derivatives has been developed. DABCO-induced demethylation can lead to 3-cyano-4-hydroxy-2-pyridones in DMF at 90°C with high yield. The protocol is applicable for the synthesis of 3-cyano-4-hydroxy-2-pyridone derivatives. The method is simple, efficient, and practical.     

Enzyme-based electrochemical biosensor for sensitive detection of DNA demethylation and the activity of DNA demethylase

A novel electrochemical method is developed for detection of DNA demethylation and assay of DNA demethylase activity. This method is constructed by hybridizing the probe with biotin tagged hemi-methylated complementary DNA and further capturing streptavidin tagged alkaline phosphatase (SA-ALP) to catalyze the hydrolysis reaction of p-nitrophenyl phosphate. The hydrolysate of p-nitrophenol (PNP) is then used as electrochemical probe for detecting DNA demethylation and assaying the activity of DNA demethylase. Demethylation of target DNA initiates a degradation reaction of the double-stranded DNA (dsDNA) by restriction endonuclease of BstUI. It makes the failed immobilization of ALP, resulting in a decreased electrochemical oxidation signal of PNP. Through the change of this electrochemical signal, the DNA demethylation is identified and the activity of DNA demethylase is analyzed with low detection limit of 1.3 ng mL⁻¹. This method shows the advantages of simple operation, cheap and miniaturized instrument, high selectivity. Thus, it provides a useful platform for detecting DNA demethylation, analyzing demethylase activity and screening inhibited drug.     

新型3-氟苯基-1H-咪唑基甲胺基衍生物的合成

以4-咪唑甲醛为原料,通过保护、格氏反应、酰化、取代、脱甲基或甲酯共5步反应合成了4种新型的3-氟苯基-1H-咪唑基甲胺基衍生物,5步总收率分别为21%、18%、22%和24%,终产物结构经1H NMR、13C NMR和HR-MS(ESI)确证。     

Design, synthesis, and incorporation of fluorous 5-methylcytosines into oligonucleotides

A palladium-catalyzed Negishi coupling reaction has been developed to synthesize fluorous 5-methylcytosines. These fluorous nucleosides are incorporated into the oligonucleotides that correspond to part of the promoter region of Oct4, a master gene that undergoes dynamic DNA demethylation during cellular reprogramming. The separation of the fluorous oligonucleotides from its nonfluorous analogues has been achieved through solid-phase extraction over fluorous silica, suggesting its potential use in probing DNA demethylation.     

Synthesis of poly(sulfonium cation) as an alkylating reagent

Methyl 4-phenylthiophenyl sulfoxide is polymerized to poly(methyl-4-phenylthiophenylsulfonium) in poly(phosphoric acid) with a yield higher than 90%. The demethylation of poly(sufonium cation) is examined to control the composition ratio of the thiophenylene unit in the polycation. The polycation is soluble in common solvents due to the alternative structure of phenylene sufide and phenylenesulfonium cation and is easily converted to poly(phenylene sulfide) through the demethylation with a nucleophile. The poly(sulfonium cation) can be applicable as an alkylating agent for phenol, aniline and benzoic acid to the corresponding to anisole, N-methyl aniline, N,N-dimethyl aniline and benzoic methyl ester, respectively, with high conversion through the demethylation. These products can be isolated without a complicated purification because poly(phenylene sulfide) is precipitated in the mixture as the side product due to the poor solvent solubility.     

The influence of clay minerals,oxides, and humic matter on the methylation and demethylation of mercury by micro-organisms in freshwater sediments

Laboratory experiments and analysis of field samples showed that clay minerals, Fe and Mn oxides, and humic matter (colloids) have complex and often dramatic effects on the microbial methylation and demethylation of Hg, and on other microbial activities, in lake sediments. Depending on the nature, abundance, and surface chemistry of the colloids, the source of the sediment, the nature of the microbes, and synergistic/antagonistic effects of environmental variables, the colloids either strongly inhibited or stimulated the Hg transformations, had little or no effect, or alternated in their effects. Most of the results suggest specific effects on particular kinds of microbes, and are not attributable to general inhibition or stimulation of microbial growth or to effects due to the binding of Hg by the colloids. The colloids probably alter the species composition of the microbial community and affect the course of ecological succession, upsetting the dynamic balance between methylation and demethylation and causing alternate increases and decreases in methyl mercury (CH₃Hg⁺) levels along with changes in other indicators of microbial activity [CO₂ and CH₄ production and oxidationreduction potential (Eh)]. The role of clays was critically dependent on surface coatings. Clays often interfered with methylation (while in some cases strongly promoting subsequent demethylation); but iron oxide (FeOOH) often promoted methylation, and FeOOH coatings on clay tended to counterbalance the negative influence of the clay. Removal of oxide coatings depressed both methylation and demethylation. Manganese oxide (MnOOH) coatings sometimes promoted methylation, but larger amounts of MnOOH (unlike FeOOH) strongly suppressed methylation. On addition of organic nutrients, oxide coatings enhanced methylation and impeded demethylation; without nutrient enrichment, the reverse tended to occur. Humic matter in solution tended to stimulate methylation; but humic coatings on clay impeded methylation and fostered demethylation. Thus, the effects of natural colloids on Hg speciation are vitally important but variable, inconsistent, and not altogether predictable.     

Importance of axial ligand in meso-tetraphenylporphinatoiron(III) promoted NO and OO bonds cleavages

Amines, especially imidazole, were found to be essential in the meso-tetraphenylporphinatoiron (III) promoted demethylation of N, N-dimethylaniline N-oxide through the Polonovski type reaction and in the cumene hydroperoxide dependent oxidative demethylation of N, N-dimethylaniline in dichloromethane. When benzenethoil was used instead of these amines, deoxygenation of N, N-dimethylaniline N-oxide took place very readily     

Demethylation of trimethylantimony species in aqueous solution during analysis by hydride generation/gas chromatography with AAS and ICP MS detection

The method of hydride generation for the speciation of antimony compounds was examined with respect to the problem of molecular "rearrangement'. Specifically, demethylation of trimethylstilbine during the analysis of trimethylantimony dichloride (Me₃SbCl₂) was studied. Previously published observations that enhanced demethylation takes place as a result of inadequate preconditioning of the analytical apparatus were found to be not reproducible. However, demethylation was enhanced as the pH decreased when using two different analytical methods: semi-continuous flow hydride generation–gas chromatography–atomic absorption spectrometry (HG– GC–AAS), and batch-type hydride generation– gas chromatography–inductively coupled plasma mass spectrometry (HG–GC–ICP MS). Applications of the hydride generation method to environmental samples revealed differences in analytical results at high and low pH, and enhanced demethylation taking place because of the matrix in a fungal extract sample. The authors recommend that researchers using the method of hydride generation for antimony compounds carefully test the reaction conditions with standard compounds and use the method of standard addition only. © 1998 John Wiley & Sons, Ltd.     

污染水产去甲基化表观遗传毒性EGFP评价方法

pEGFP-C3质粒经过体外人工甲基化处理后,被转染进入HepG2细胞以构建重组细胞株．以5-AZA为阳性去甲基化毒物与重组细胞共培养,通过亚硫酸氢钠测序法定量检测EGFP基因启动子区甲基化状态,通过实时定量PCR检测EGFP基因表达,借助流式细胞术和荧光摄片定量检测共培养细胞的绿色荧光强度,在DNA甲基化、EGFP基因mRNA表达、GFP蛋白等多个层次研究5-AZA染毒处理与其去甲基化能力和荧光表达改变的响应关系．对天津污染水产的去甲基化能力进行了实际样品测试．结果表明,5-AZA与重组细胞的DNA甲基化、基因表达、蛋白产物变化之间存在显著关联,具有较低的检出浓度和良好的重复性．天津污染海域的水产去甲基化能力较强．本文初步建立了一种污染物去甲基化表观遗传毒性评价方法．     

What Is the Catalytic Mechanism of Enzymatic Histone N-Methyl Arginine Demethylation and Can It Be Influenced by an External Electric Field?

Arginine methylation is an important mechanism of epigenetic regulation. Some Fe(II) and 2-oxoglutarate dependent Jumonji-C (JmjC) Nϵ-methyl lysine histone demethylases also have N-methyl arginine demethylase activity. We report combined molecular dynamic (MD) and Quantum Mechanical/Molecular Mechanical (QM/MM) studies on the mechanism of N-methyl arginine demethylation by human KDM4E and compare the results with those reported for N-methyl lysine demethylation by KDM4A. At the KDM4E active site, Glu191, Asn291, and Ser197 form a conserved scaffold that restricts substrate dynamics; substrate binding is also mediated by an out of active site hydrogen-bond between the substrate Ser1 and Tyr178. The calculations imply that in either C−H or N−H potential bond cleaving pathways for hydrogen atom transfer (HAT) during N-methyl arginine demethylation, electron transfer occurs via a σ-channel; the transition state for the N−H pathway is ∼10 kcal/mol higher than for the C−H pathway due to the higher bond dissociation energy of the N−H bond. The results of applying external electric fields (EEFs) reveal EEFs with positive field strengths parallel to the Fe=O bond have a significant barrier-lowering effect on the C−H pathway, by contrast, such EEFs inhibit the N−H activation rate. The overall results imply that KDM4 catalyzed N-methyl arginine demethylation and N-methyl lysine demethylation occur via similar C−H abstraction and rebound mechanisms leading to methyl group hydroxylation, though there are differences in the interactions leading to productive binding of intermediates.     

An efficient synthesis of the phytoestrogen 8-prenylnaringenin from xanthohumol by a novel demethylation process

8-Prenylnaringenin, a flavonoid, is the strongest known phytoestrogen (plant derived estrogen mimic) used in phytomedicinal applications. Starting from xanthohumol a byproduct of hops-extraction, 8-prenylnaringenin can be synthesized via isoxanthohumol. Of various demethylation procedures tested, the best yield (92%) is obtained by treatment with scandium trifluoromethanesulfonate and potassium iodide without any need of protection. The demethylation with AlBr₃/collidine and of the TIPS protected isoxanthohumol provides good results too.     

Demethylation reactions of 4-amino-N-(2,6-dimethoxy-4-pyrimidinyl)benzenesulfonamide (sulfadimethoxine) in strongly basic aqueous solution

Hydrolysis of 1 in strongly basic aqueous solution afforded mono- and didemethylated products 2,3 and 4 , that are postulated as the metabolites of 1 in some animals. This hydrolytic demethylation was shown to proceed stepwise via mono-demethylation to give 2 and 3 , followed by their further demethylation to 4 . The hydrolytic reactivity of 1–3 was rationalized based on MO calculation results and ¹³C nmr data.     

Efficient One‐Pot Synthesis of Hydroxyflavanones by Cyclization and O‐Demethylation of Methoxychalcones

An efficient one‐pot method for the synthesis of hydroxyflavanones is described. Methoxychalcones are treated with 36% HBr to afford cyclization and regioselective O‐demethylation products (2a–i) while cyclization and complete O‐demethylation products (3a–e) are obtained in the presence of 45% HI.     

Demethylation of methylarsenic species by Mycobacterium neoaurum

Mycobacterium neoaurum demethylates both methylarsonic acid and methylarsonous acid to mixtures of arsenate and arsenite. After 28 days of incubation, the yields of inorganic arsenic were 27% from arsenate and 43% from arsenite. A time study of the demethylation of methylarsonic acid by M. neoaurum showed that demethylation occurs rapidly during the growth and stationary phases of the bacterium, and indicates that MMA(V) is reductively demethylated to arsenite. Copyright © 2003 John Wiley & Sons, Ltd.     

An Alternate Synthesis of 4-Hydroxybenzocyclobutene

4-Hydroxybenzocyclobutene was prepared in good yield from the demethylation of 4-methoxybenzocyclobutene with aluminum iodide in acetonitrile.     

Moosinhaltsstoffe—XVIII : Synthese von pellepiphyllin und lunularin

2-Hydroxy-3,4′-dimethoxybibenzyl (=pellepiphyllin) and 3,4′-dihydroxybibenzyl (=lunularin) have been synthesized by Wittig type reactions. Condensation of 2,3-dimethoxybenzaldehyde with 4-methoxybenzylphosphonate to 2,3,4′ trimethoxystibene, catalytic reduction to 2,3,4′-trimethoxybibenzyl, demethylation to 2,3,4′-trihydroxybibenzyl and partial methylation yields pellepiphyllin. Lunularin was synthesized by reaction of 3-methoxybenzaldehyde with 4-methoxybenzylphosphonate to 3,4′-dimethoxystilbene, catalytic hydrogenation to 3,4′-dimethoxybibenzyl and demethylation with boron tribromide.     

An efficient method for demethylation of aryl methyl ethers

A new efficient method for demethylation of aryl methyl ethers using iodocyclohexane in DMF under reflux condition is described.     

Identification of the constituents and metabolites in rats after oral administration of Zi Shen Formula by UPLC‐Q‐TOF/MS combined pattern recognition analysis

An ultra‐high‐performance liquid chromatography mass spectrometry method was established to detect and identify the chemical constituents of Zi Shen Formula (ZSF) and its metabolites in serum, urine and feces, after oral administration to rats. A total of 68 compounds were characterized in ZSF extracts. In vivo, 38 prototype components and 32 metabolites of ZSF were tentatively identified in rat serum, urine and feces. Seven metabolic pathways including demethylation, hydroxylation, oxidation, sulfation, glucuronidation, methylation and de‐caffeoyl were proposed to be involved in the generation of these metabolites. It was found that glucuronidation, methylation and demethylation were the major metabolic processes of alkaloids, while demethylation, methylation, sulfation and de‐caffeoyl were the major metabolic pathways of phenylethanoid glycosides. The main metabolic pathways of steroidal saponins were oxidation and isotype reactions. These findings are significant for our understanding of the metabolism of ZSF. The proposed metabolic pathways of bioactive components might be crucial for further studies of the mechanisms of action and pharmacokinetic evaluations of ZSF.     

Selective Demethylation and Demethoxy Thioalkylation of 5-Methoxyindoles

Under appropriate conditions, hard acid and soft nucleophile system lead to selective demethylation and demethoxy- thioalkylation of certain 5-methoxyindoles.