Nuclear Alkylation Research Articles

The DNA damage response is developmentally regulated in the African trypanosome

Genomes are affected by a wide range of damage, which has resulted in the evolution of a number of widely conserved DNA repair pathways. Most of these repair reactions have been described in the African trypanosome Trypanosoma brucei, which is a genetically tractable eukaryotic microbe and important human and animal parasite, but little work has considered how the DNA damage response operates throughout the T. brucei life cycle. Using quantitative PCR we have assessed damage induction and repair in both the nuclear and mitochondrial genomes of the parasite. We show differing kinetics of repair for three forms of DNA damage, and dramatic differences in repair between replicative life cycle forms found in the testse fly midgut and the mammal. We find that mammal-infective T. brucei cells repair oxidative and crosslink-induced DNA damage more efficiently than tsetse-infective cells and, moreover, very distinct patterns of induction and repair of DNA alkylating damage in the two life cycle forms. We also reveal robust repair of DNA lesions in the highly unusual T. brucei mitochondrial genome (the kinetoplast). By examining mutants we show that nuclear alkylation damage is repaired by the concerted action of two repair pathways, and that Rad51 acts in kinetoplast repair. Finally, we correlate repair with cell cycle arrest and cell growth, revealing that induced DNA damage has strikingly differing effects on the two life cycle stages, with distinct timing of alkylation-induced cell cycle arrest and higher levels of damage induced death in mammal-infective cells. Our data reveal that T. brucei regulates the DNA damage response during its life cycle, a capacity that may be shared by many microbial pathogens that exist in variant environments during growth and transmission.

Formation of ethyl benzene and styrene by side chain methylation of toluene over calcined LDHs

Mg/Al layered double hydroxide (LDH) with various Mg/Al molar ratios 3, 4, 5, 7 and 10 were prepared, calcined and characterized by XRD, FT-IR, ICPES and BET surface area analysis. These LDHs were used for side chain methylation of toluene with methanol between 300 and 450 °C. For comparison, Cu/Al, Ni/Al, Co/Al and Zn/Al LDHs with molar ratio 3 were also prepared. The selectivity of styrene was higher over Mg/Al with low Al content. The selectivity of ethyl benzene was higher at 400 °C. At higher temperature, the side chain alkylation was favored and the selectivity of nuclear alkylation products such as xylene and mesitylene decreased as Mg/Al ratio changes from 3 to 10. The enhanced activity of calcined LDHs is due to the surface sites of low (OH − groups), medium (Mg–O pairs), and strong (O 2− anions) basicity. The surface concentration of low and medium strength basic sites increased with decreasing Al content. On Mg/Al LDHs, nuclear alkylation increased with increasing Al content. Substitution of Co 2+, Ni 2+, Zn 2+ and Cu 2+ for Mg 2+ favored nuclear alkylation. The selectivity of xylene and mesitylene increased with increase in temperature at a maximum 400 °C. Mg/Al LDHs were the most LDHs active than other LDHs for side chain methylation of toluene.

Synthese und Eigenschaften der s‐Triazolo[1,5‐a]pyrimidine

Abstracts‐Triazolo[1,5‐a]pyrimidines are important stabilizers for photographic silver halide emulsions and are used for pharmaceutical and agrochemical purposes, too. In the report it is dealt with syntheses from s‐triazoles and from pyrimidines, physical properties, tautomerism, nuclear alkylation, electrophilic and nucleophilic substitution, ring fission and other reactions, and applications.

Importance of phospholipids to nitrosourea interactions with the nuclear envelope and associated nucleic acids.

Nuclease digestion of triton isolated HeLa cell nuclei has resulted in nuclear envelopes containing less than 10% of the nuclear macromolecule. Alkylation and carbamoylation of the nuclear envelope (NE) fraction by chloroethylnitrosoureas (HNU) was disproportionately high (approximately 35% of total nuclear alkylation and approximately 55% carbamoylation) suggesting that the nucleophilic species in the envelope were preferential targets for drug binding. Digestion of the envelope fraction with phospholipase C (PLC), followed by buoyant density gradient separation in Percoll (70%):0.15 M NaCl (30%), demonstrated that some envelope:nucleic acid attachments were destabilized as a result of phospholipid cleavage. In addition, the buoyant density of HNU-modified NE macromolecules was slightly altered by PLC digestion, suggesting that cleavage of polar phospholipids did not completely destabilize the chloroethylated products from the nuclear envelope.

Stereochemical Studies on the Nuclear Alkylation of Phenols with 1-Phenylethyl Chloride and the Acidic Rearrangement of the 1-Phenylethyl Ethers of Phenols in the Phenolic Solvents

Abstract Phenolyses of optically active 1-phenylethyl chloride were carried out in phenol (50°C), p-cresol (100°C), p-chlorophenol (100°C), and 2,6-xylenol (100°C in the presence of variable concentrations of the sodium salts of the respective phenols or triethylamine; the distributions (%) for the O- and C-alkylation products and the net steric courses (α%) for each product were examined. The distribution and the steric course which were graphically extrapolated to the zero base concentration indicated that, if the influence of the liberated hydrogen chloride was excluded, in the phenolyses without an added base the major products are the 1-phenylethyl ethers of the respective phenols with net retained configurations and the minor products are the o-and p-1-phenylethylated phenols with net inverted configurations. The hydrogen chloride rearrangement of the optically active 1-phenylethyl ethers of the respective phenols proceeded rapidly to give o-1-phenylethylated phenols with predominantly retained configurations (for phenol, p-cresol, and p-chlorophenol) and p-1-phenylethylated phenols with net inverted configurations (for phenol and 2,6-xylenol) in the respective phenol–benzene (1:1 by wt) solvents. The p-toluenesulfonic acid rearrangement of 1-phenylethyl phenyl ether-18O proceeded to give o- and p-1-phenylethylphenols with partial loss of the oxygen-18 atom in the phenol–benzene (1:1 by wt) solvent, indicating the coexistence of the intermolecular course for the acidic rearrangement in the phenolic solvents. From these findings, it is concluded that the formation of the ortho-alkylates with retention of configuration, experimentally observed in the respective phenolyses without an added base, is attributed not to the direct retentive alkylation of the phenols, but to the rapid rearrangement of the 1-phenylethyl ethers with net retention of configuration, caused by the hydrogen chloride liberated in the SN1-phenolysis of 1-phenylethyl chloride in the respective phenolic solvents.

The nuclear alkylation of pyrazines by ketones and aldehydes

Aldehydes and ketones in the presence of a solution of an alkali- or alkaline earth-metal in liquid ammonia, or a suspension of these metals in other solvents, can be used to alkylate the pyrazine ring in moderate to good yields. This alkylation has been successfully applied to pyrazine itself and to alkyl-, dialkyl-, amino- and methoxy-pyrazines. A mechanism for the reaction is proposed.

The friedel-crafts condensation of the lactone of 4-methyl-2-hydroxycyclohexane acetic acid with aromatic hydrocarbons-I : VBenzene and toluene

The cationic nuclear alkylation of benzene with the lactone (I) has been found to give a stereoisomeric mixture containing 4-methyl-2-phenylcyclohexyl acetic acid (II) and 4-methyl-3-phenylcyclohexyl acetic acid (III). The former has been cyclized, reduced and dehydrogenated to 3-methyl phenanthrene. A similar condensation between the lactone (I) and toluene afforded a mixture of 4-methyl-2- o-tolyl-, 4-methyl-2- p-tolyl- and 4-methyl-3- p-tolyl-cyclohexyl acetic acids. The structures of the former two acids were confirmed by their cyclization to ketohydrophenanthrenes (VIII) and (IX) and their subsequent conversion to 3,5-dimethyl- and 2,6-dimethyl phenanthrenes respectively. A possible mechanism for the abnormal Friedel-Crafts reaction is discussed.

Reactions of alkyl radicals. Part II. Reactions of alkylbenzenes with methyl radicals. Photolytic formation and reactions of ethyl and n-butyl radicals

Several aromatic solvents have been alkylated using the photolysis of methyl-, ethyl-, and n-butyl-mercuric iodide as the sources of alkyl radicals. The relative proportions of nuclear and side-chain attack on toluene and on isopropylbenzene, and the distribution of the isomeric products of nuclear alkylation of toluene and of chlorobenzene are in agreement with the postulate that alkyl radicals are more nucleophilic than aryl radicals. The mechanism of formation of α-methylstyrene, as well as bicumyl, by side-chain attack on cumene is discussed.

The nuclear alkylation of arylamines by trialkyl phosphates

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Nuclear Alkylation of Salts of Naphthols and Anthranol1

Nuclear Alkylation of Salts of Naphthols and Anthranol¹

Resorcinolの置換に関する研究 (第2報)

1) By the nuclear methylation of resacetophenone, 3-methyl-2, 4-dihydroxyacetophenone was obtained from which it has become clear that 3-methyl-2-hydroxy-4-methoxyacetophenone, obtained to date by the same reaction, had been formed by the etherification of the dihydroxy derivative.2) In the nuclear methylation of resacetophenone, the chief product is paeonol when the molar ratio of resacetophenone, potassium hydroxide, and methyl iodide is equimolar or thereabouts, but the yield of 3-methyl-2-hydroxy-4-methoxyacetophenone increases as the molar ratio of potassium hyroxide and methyl iodide to resacetophenone increases, becoming the maximum at 2.5 moles of potassium hydroxide and 4 moles of methyl iodide to 1 mole of resacetophenone. There is no necessity for the great excess of methyl iodide.3) In order to examine the reactivity of the 3-position in nuclear alkylation of resacetophenone, Legal and Ehrlich reactions of resacetophenone and its allied compounds were carried out.

Stereochemical Evidence for a Concerted Displacement Mechanism in Acidic Aromatic Alkylations. The Nuclear Alkylation of Phenols with α-Phenethyl Chloride1

Stereochemical Evidence for a Concerted Displacement Mechanism in Acidic Aromatic Alkylations. The Nuclear Alkylation of Phenols with α-Phenethyl Chloride¹

Nuclear Alkylation in the Alkali-catalyzed Reaction of Styrene Oxide with 2-Naphthol

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNuclear Alkylation in the Alkali-catalyzed Reaction of Styrene Oxide with 2-NaphtholCyrus O. Guss and Leonard H. JulesCite this: J. Am. Chem. Soc. 1950, 72, 9, 3878–3880Publication Date (Print):September 1, 1950Publication History Published online1 May 2002Published inissue 1 September 1950https://doi.org/10.1021/ja01165a013RIGHTS & PERMISSIONSArticle Views65Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (378 KB) Get e-Alerts Get e-Alerts

Hydrogen Fluoride as a Condensing Agent. III. Nuclear Alkylation of Thiophenes in the Presence of Hydrogen Fluoride1

Hydrogen Fluoride as a Condensing Agent. III. Nuclear Alkylation of Thiophenes in the Presence of Hydrogen Fluoride¹

6. The nuclear alkylation of aromatic bases. Part V. The action of methyl alcohol on m-toluidine hydrochloride

6. The nuclear alkylation of aromatic bases. Part V. The action of methyl alcohol on m-toluidine hydrochloride

81. The nuclear alkylation of aromatic bases. Part IV. The action of n-dodecyl alcohol on the hydrochlorides of α- and β-naphthylamine

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397. The nuclear alkylation of aromatic bases. Part III. The action of methyl alcohol on the hydrochlorides of α- and β-naphthylamine

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134. The nuclear alkylation of aromatic bases. Part II. The action of methyl alcohol on the hydrochlorides of 2- and 4-aminodiphenyl

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CCXVII.—The nuclear alkylation of aromatic bases. Part I. The action of methyl alcohol on the hydrochlorides of o- and p-toluidine, mesidine, and dimethylmesidine

CCXVII.—The nuclear alkylation of aromatic bases. Part I. The action of methyl alcohol on the hydrochlorides of o- and p-toluidine, mesidine, and dimethylmesidine