Synthesis of 5,6-dimodified open-chain d-fructose derivatives and their properties as substrates of bacterial polyol dehydrogenase

5-Deoxy-5-fluoro-d-xylulose as well as a range of new 5,6-dimodified open-chain analogues of d-fructose, namely the 5,6-diazido-5,6-dideoxy, 6-azido-5,6-dideoxy, 6-azido-5,6-dideoxy-5-fluoro, 5,6-dideoxy-5-fluoro, 5,6-dideoxy-6-fluoro and 5,6-dideoxy-5,6-difluoro derivatives, were synthesised employing glucose isomerase catalysed isomerisation of the corresponding d-xylo- and d-glucofuranoses as a key step. New compounds as well as some previously reported analogues such as 5-azido-5,6-dideoxy-6-fluoro-d-fructose were shown to be excellent substrates of polyol dehydrogenase from Burkholderia cepacia DSM 50181 with K_m values two orders of magnitude smaller than the corresponding natural substrates.     

Derivatives of condensed pyrimidine,pyrazine, and pyridine systems

Reaction of 2-mercapto-3-amino-5,6-dimethyl- and 2-mercapto-3-amino-5,6-diphenylpyrazines withα-halo acid esters gave 2-carbethoxy-3-aminopyrazines, which are converted by the action of sodium ethoxide to 5,6-dimethyl- and 5,6-diphenylpyrazino[2,3-b]-[1,4]thiazin-6-ones. The latter are more conveniently obtained from 2-chloro-3-amino-5,6-dimethyl- and 2-chloro-3-amino-5,6-diphenylpyrazines and thioglycolic acid. 5,6-Dihydropyrazinothiazine is formed by reduction of 5,6-dimethyl pyrazino[2,3-b][1,4]thiazin-6-one, whereas the 2,3-dimethyl-5-amino-6-sulfonic acid and its N-oxide are formed by oxidation.     

A new synthesis of 5-hydroxy-6-methyluracil

Dehydration of 5,6-dihydro-5,6-dihydroxy-6-methyl- and 5,6-dihydro-5,6-dihydroxy-1,3,6-trimethyl-uracil in 0.4 M aqueous sulfuric acid gives 5-hydroxy-6-methyl- and 5-hydroxy-1,3,6-trimethyluracil in quantitative yields. Two possible mechanisms have been examined using the mPW1k/6-311+G(2df,2pd)//mPW1k/6-31+G(d,p) method for the transformation of methylated and non-methylated 5,6-dihydro-5,6-dihydroxy-6-methyluracils into the corresponding 5-hydroxy-6-methyluracils. The first is a hydride C5-C6 shift occurring in concert with the loss of a water molecule and formation of the corresponding protonated 5,6-dihydro-5-oxo-6-methyluracils. The second is an acid-catalyzed dehydration reaction to yield 5-hydroxy-6-methyluracils. The calculations demonstrated that the second pathway was energetically most favorable.     

Oxidation of 4-styryl- 2- phenyl-5, 6-benzoquinoline with potassium permanganate

Oxidation of 4-styryl-2-phenyl-5,6-benzoquinoline with potassium permanganate gave phenyl 2-phenyl-5,6-benzo-4-quinolyl diketone, 2-phenyl-4-formyl-5,6-benzoquinoline, 2-phenyl-5,6-benzocinchoninic acid, and benzoic acid. It is shown that phenyl 2-phenyl-5,6-benzo-4-quinolyl diketone is cleaved under the influence of OH^? ions to the corresponding aldehydes and carboxylic acids; this is explained by the decisive effect of the acidity of the media on the direction of the reaction.     

Reversed-phase high-performance liquid chromatography-thermospray mass spectrometry of radiation-induced decomposition products of thymine and thymidine.

High-performance liquid chromatography-thermospray mass spectrometry was applied to the analysis of various radiation-induced decomposition products of thymidine including N-(2-deoxy-beta-D-erythro-pentofuranosyl)formamide and the various diastereomers of 5,6-dihydroxy-5,6-dihydrothymidine, 5-hydroxy-5,6-dihydrothymidine and 5,6-dihydrothymidine. This method combines high sensitivity and product resolution, rendering it particularly useful for monitoring the formation of radiation-induced base damage within DNA.     

Irregular linear sesquiterpene dilactones from Anthemis auriculata Boiss

Seven new irregular linear sesquiterpene lactones, epi-antheindurolide A (1), epi-antheindurolide A-5,6-oxide (2), 5-hydroxy-5,6-dihydro-6,13-dehydro-epi-antheinduro lide A (3), 5-hydroperoxy-5,6-dihydro-6,13-dehydro-epi-antheindurolide A (4), epi-antheindurolide B (5), 6-hydroxy-5,6-dihydro-4,5-dehydro-epi-antheindurolide A (6) and 6-hydroperoxy-5,6-dihydro-4,5-dehydro-epi-antheindurolide A (7), were isolated from the flowers of Anthemis auriculata Bioss. Their structures were established by spectroscopic techniques. The discussed compounds were found to be stereoisomers of recently reported lactones for A. arvensis.     

The synthesis of 2-chloro-1-β-D-ribofuranosyl-5,6-dimethylbenzimidazole and (certain related derivatives

The synthesis of 2-chloro-1-(β-D -ribofuranosyl)-5,6-dimethylbenzimidazole (3b) has been accomplished by a condensation of 1-trimethylsilyl-2-chloro-5,6-dimethylbenzimidazole (1) with 2,3,5-tri-O-acetyl-D -ribofuranosyl bromide (2) followed by subsequent deacetylation. Nucleophilic displacement of the 2-chloro group from 3b has furnished several interesting 2-substituted-1-(β-D -ribofuranosyl)-5,6-dimethylbenzimidazoles. 1-(β-D -Ribofuranosyl)-5,6-dimethylbenzimidazole (5) and 1-(β-D -ribofuranosyl)-5,6-dimethylbenzimidazole-2-thione (4) were prepared from 3b. Alkylation of 4 furnished certain 2-alkylthio-1-(β-D -ribofuranosyl)-5,6-dirnethylbenzimidazoles and oxidation of 4 with alkaline hydrogen peroxide produced 1-(β-D -ribofuranosyl)-5,6-dimethylbenzimidazole-2-one D The assignment of anomeric configuration for all nucleosides reported is discussed.     

Regioselective dibromination of methyl indole-3-carboxylate and application in the synthesis of 5,6-dibromoindoles

Treatment of methyl indole-3-carboxylate with bromine in acetic acid gives methyl 5,6-dibromoindole-3-carboxylate regioselectively, from which the parent 5,6-dibromoindole can be accessed via a one-pot, microwave-mediated ester hydrolysis and decarboxylation. Application of these building blocks in syntheses of natural and non-natural 5,6-dibromoindole derivatives, including meridianin F and 5,6-dibromo-2'-demethylaplysinopsin, is reported.     

Concise syntheses of 2-aminoindans via indan-2-ol

2-Amino-5,6-dimethoxyindan hydrochloride was synthesized in seven steps and with an overall yield of 48%. Indan-2-ol was converted to 5,6-dibromo-indan-2-ol in three steps by acetylation, electrophilic bromination and deacetylation. Dimethoxylation of 5,6-dibromoindan-2-ol with NaOCH₃ in the presence of CuI gave 5,6-dimethoxy-indan-2-ol, which was converted to 2-amino-5,6-dimethoxyindan hydrochloride by azidation, followed by Pd-C catalyzed hydrogenation. Similarly, 2-amino-5-bromoindan was synthesized in five steps and with an overall yield of 50%. Indan-2-ol was converted to 2-aminoindan by azidation followed by Pd-C catalyzed hydrogenation. The reaction of 2-aminoindan with 2.5 equiv Br₂ afforded 2-amino-5,6-dibromoindan.     

Simple and regioselective bromination of 5,6-disubstituted-indan-1-ones with Br2 under acidic and basic conditions

Bromination of 5,6-dimethoxyindan-1-one with Br(2) in acetic acid at room temperature produced exclusively the corresponding 2,4-dibromo compound in 95% yield. Reaction of 5,6-dimethoxyindan-1-one with Br(2) in the presence of KOH, K(2)CO(3) or Cs(2)CO(3 )at ~0 degrees C( )gave the monobrominated product 4-bromo-5,6-dimethoxyindan-3-one in 79%, 81% and 67% yield, respectively. 5,6-Dihydroxyindan-1-one was dibrominated on the aromatic ring affording 4,7-dibromo-5,6-dihydroxyindan-1-one both in acetic acid at room temperature and in the presence of KOH at ~0 degrees C. 5,6-Difluoroindan-1-one and 1-indanone were alpha-monobrominated in acetic acid and alpha,alpha-dibrominated under KOH conditions at room temperature.     

5,6-二甲基-2,3-吡嗪二甲酰胺-铜配合物的合成及其抗菌活性

以2,3-二甲基-5,6-二氰基吡嗪为原料,稀碱条件下不完全氧化得到配体5,6-二甲基-2,3-吡嗪二甲酰胺,再与醋酸铜在弱碱条件下合成5,6-二甲基-2,3-吡嗪二甲酰胺-铜配合物;采用牛津杯法预试验及试管二倍稀释法研究配体5,6-二甲基-2,3-吡嗪二甲酰胺及其配合物的抗菌活性。 对合成的配合物通过紫外光谱、红外光谱、差热-热重分析进行确证表征。 该配合物表现出较好的抑菌和杀菌作用,对大肠埃希菌的MIC和MBC均为50 mg/L,对金黄色葡萄球菌的MIC和MBC均为25 mg/L,而配体没有明显的抑菌杀菌作用,从而为临床疾病的治疗和食品添加剂的研发提供参考。     

π-Electron manipulation of the 5,6-dihydroxyindole/quinone system by 3-alkynylation: mild acid-mediated entry to (cross)-conjugated scaffolds and paradigms for medium-tunable chromophores

5,6-Dihydroxyindole-based systems engender increasing interest for the design and implementation of new functional aromatic scaffolds and eumelanin-like materials with tailored absorption and electronic properties. However, studies aimed at elucidating the influence of external π-conjugating groups on the redox properties and acid-induced reactivity of these highly oxidizable indolic platforms are lacking. We report herein the synthesis (as acetyl derivatives) and chemical/quantum chemical characterization of the first π-extended 5,6-dihydroxyindole derivatives, 3-ethynyl-5,6-dihydroxyindole (1) and 3,3'-(1,2-ethynediyl)bis-5,6-dihydroxyindole (2), in order to understand whether and how β extension of the enamine-like pyrrole sector affects the absorption properties, redox behavior, and protonation equilibria at both the o-diphenol and quinone levels. Oxidation of 1 and 2 proceeded smoothly to generate dark insoluble materials with eumelanin-like UV properties. On exposure to phosphate buffer at pH 3, 1 was rapidly converted to 3-acetyl-5,6-dihydroxyindole (5) and, in the presence of 5,6-dihydroxyindole, to the cross-conjugated 3,3'-ethenylidenebis-5,6-dihydroxyindole (6). DFT calculations on 1 and 2 and their quinones in their pristine states and after protonation provided a mechanistic frame to rationalize the unusual acid-mediated chemistry of 1 and disclosed 2-quinone as the prototype of a novel class of medium-dependent chromophores. The ethynyl(ene) structural motif is thus proposed as the key to new tunable π-electron extended 5,6-dihydroxyindole/5,6-indolequinone paradigms for the rational design of alkyne-containing hybrid eumelanin-type polymers.     

Concise syntheses of 5,6-dibromotryptamine and 5,6-dibromo-N,N-dimethyltryptamine en route to the antibiotic alternatamide D

Concise syntheses of the natural products 5,6-dibromotryptamine, 5,6-dibromo-N,N-dimethyltryptamine and the bromotryptamine antibiotic alternatamide D have been accomplished starting from the common intermediate, 5,6-dibromoindole-3-carbaldehyde.     

一种功能型混配镍配合物的溶剂化显色特性与结构关系

详细报道了新近合成的二氰基二硫纶·邻菲罗啉二酮合镍配合物Ni(mnt) (phen - 5,6-dione) (mnt2 - ∶1,2 -dicyano - 1,2 -ethylenedithiolateormaleonitriledithiolate ;phen - 5,6-dione∶1,10 -phenanthroline - 5,6-dione)的电子吸收光谱 ,着重研究了可见光区中的溶剂化显色吸收带在相关分子轨道能级图中的对应跃迁关系 ,探讨了LL′CT的本质和感光氧化现象。     

Oxidation chemistry and biochemistry of some biologically important purines and indoleamines

The electrochemical oxidation of 7-methyluric acid and 5,6-dihydroxytryptamine (5,6-DHT) in aqueous solutions has been studied. The oxidation products have been separated and characterized using melting point, mass, ¹H nuclear magnetic resonance and spectral studies, and tentative mechanisms for the oxidation have been suggested. One of the oxidation products of 5,6-DHT, i.e. 2,7′-bi(5,6-DHT), has been found to produce a substantial neurotoxic effect in mice brain.     

Stereoselective synthesis of 5,6-disubstituted 5,6-dihydro-1,10-phenanthrolines and a rare example of axially constrained 2,2′-bipyridines

The stereoselective synthesis of 5,6-disubstituted 5,6-dihydro-1,10-phenanthrolines and (5S,6S)-5,6-dihydroxy-5,6-dihydro-1,10-phenanthroline cyclic o-xylylene diether, a rare example of an axially constrained 2,2′-bipyridine is reported. The strategy to obtain such compounds is based on two highly efficient reactions, the Sharpless asymmetric dihydroxylation and the Ullmann intramolecular coupling.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

Synthese von (−)-(5R,6S)-5,6-Epoxy-5,6-dihydro-β-ionon

Synthesis of (?)-(5R,6S)-5,6-epoxy-5,6-dihydro-β-ionone Optically active 5,6-epoxy-5,6-dihydro-β-ionones have been prepared for the first time and their absolute configurations were determined by correlation with (?)-(S)-α-ionone. Acid catalyzed hydrolysis of the epoxide proceeds with retention of the configuration at C(6) and with inversion at C(5).     

5,6-Trimethylenethiapyrylium and 5,6,7,8-tetrahydrothiochromylium salts

5,6-Trimethylenethiapyrylium salts have been obtained for the first time. 5,6-Trimethyleneγ-thiopyrans (or 5,6,7,8-tetrahydro-γ-thiochromenes), which belong to a previously unknown series of two-ring sulfides, are formed by reaction of the 5,6-trimethylenethiapyrylium salts (or 5,6,7,8-tetrahydrothiochromylium salts) with Grignard reagents and lithium aluminum hydride.     

Formylation of indol-1-yl acetates

Preparation procedure was developed for 3-formylindole-5,6-dicarbonitriles underlain by the treatment of 1-acetoxyindole-5,6-dicarbonitriles with Vilsmeier-Haack reagent; a special feature of this reaction consisted in a replacement of the OAc group for hydrogen. A probable mechanism was assumed of the formation of 3-formylindole-5,6-dicarbonitriles.