Synthesis and chromatographic study of methyl-2,3-O-isopropylidene-5-dimethyl-arsinoyl-β-d-ribofuranoside and methyl-2,3-O-isopropylidene-5-deoxy-5-dimethyl-thioarsinoyl-β-d-ribofuranoside

The synthesis of two riboside-containing arsenic compounds, methyl-2,3-O-isopropylidene-5-dimethyl-arsinoyl-β-d-ribofuranoside and methyl-2,3-O-isopropylidene-5-deoxy-5-dimethyl-thioarsinoyl-β-d- ribofuranoside is presented in this paper. Intermediates and final products of the synthesis were examined by gas chromatography and thin layer chromatography. The purity of the products was assessed by NMR spectroscopy. Trimethylsilylation was used to volatilise sugar compounds and thus use of the costly HPLC–MS technique was avoided. The results affirmed the presence of tautomers in case of arsenosugars.     

Heterocyclic analogs of 5,12-naphthacene-quinone. 3. Synthesis of 4,11-diaminonaphtho-[2,3-f]indole-5,10-dione and certain of its derivatives

Nucleophilic substitution of methoxy groups in 4,11-dimethoxynaphtho[2,3-f]indole-5,10-dione by the action of primary and secondary alkylamines, or arylamines leads to the formation of N-alkyl or N-aryl derivatives of 4,11-diaminonaphtho[2,3-f]indole-5,10-dione respectively. 4,11-Diamino-1H-naphtho-[2,3-f]indole-5,10-dione is obtained by the dealkylation of 4,11-bis[(1-phenylethyl)amino]-1Hnaphtho[ 2,3-f]indole-5,10-dione in the presence of a Lewis acid (BBr₃). __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 854–861, June, 2006.     

Synthesis of functionalized pyrimidine-4-thiones and derivatives of pyrido[2,3-d]pirimidine-5-one from monoacylketene aminals

Monoacylketene aminals containing an unsubstituted NH₂ group react as C-nucleophiles with benzoyl isothiocyanate to give the corresponding thioamides which undergo cyclization by sodium methoxide in methanol to afford 6-R-amino-5-acetyl-2-phenyl-3H-pyrimidine-4-thiones. A scheme for constructing the pyrido[2,3-d]pyrimidine system from keteneaminals is offered. The reaction of 6-R-amino-5-acetyl-2-phenyl-3H-pyrimidine-4-thiones with dimethylformamide dimethylacetal leads to 8-R-N-4-methylthio-8H-pyrido-[2,3-d]pyrimidine-5-ones. Cyclization of 5-acetyl-6-benzoylamino-4-methylthio-2-phenylpyrimidine by sodium methoxide yields N-unsubstituted 4-methylthio-8H-pyrido-[2,3-d]pyrimidine-5-one.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1932–1937, November, 1993     

Some chemical properties of 2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-one and 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones

We have studied the reaction of 2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-one and 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones with amines, alkylating reagents, and hydrogen peroxide. We have shown that the presence of an aryl substituent at the 2 position of [1,3-thiazino[3,2-a]benzimidazol-4-ones has a substantial effect on the direction of the reactions. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 445–452, March, 2006.     

Heterocyclic analogs of 5,12-naphthacenequinone. 5. Synthesis of 2,3-diamino-1,4-dimethoxyanthraquinone and its heterocyclic derivatives

A new method for the synthesis of 2,3-diamino-1,4-dimethoxyanthraquinone from quinizarin has been developed. Heterocyclic analogs of 5,12-naphthacenequinone have been synthesized based on this o-diamine-4,11-dimethoxyanthra[2,3-d]imidazole-5,10-dione, 4,11-dimethoxyanthra[2,3-d][1,2,3]triazole-5,10-dione, and 5,12-dimethoxynaphtho[2,3-g]quinoxaline-6,11-dione. On the 70th Birthday of Professor E. Lukevics. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.1, 96–102, January 2007.     

Synthesis and chemical transformations of 2,3-dihydropyrrole-2,3-diones annelated on the [a] side by azaheterocycles. (Review)

Data on methods for the synthesis of 2,3-dihydro-2,3-pyrrolediones condensed with azaheterocycles on the [a] side are reviewed. Their reactions with nucleophilic reagents, allylboronation, reduction, and thermal transformations are discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 3–25, January, 2006.     

Reactions of 2,3-Dioxopyrrolo[2,1-a]isoquinolines with Ammonia and Aliphatic Amines

2,3-Dioxopyrrolo[2,1-a]isoquinolines, with either a tertiary amide substituent at position 1 or no substituent, react with ammonia and aliphatic amines with ring opening to form the corresponding enamino keto amides.     

Application of cyclic-1,3-diketones in domino and multicomponent reactions: facile route to highly functionalized chromeno[2,3-d]pyrimidinones and diazabenzo[b]fluorenones under solvent-free conditions

A facile and efficient protocol for the synthesis of chromeno[2,3-d]pyrimidinones and diazabenzo[b]fluorenones has been developed by one-pot three-component cyclocondensation of aldehydes, cyclic-1,3-diketones and 1,3-dimethylbarbituric acid in the presence of InCl₃ or P₂O₅ under solvent-free conditions.     

N-alkylation of 2,3-dihydroimidazo[2,1-b]quinazolin-1(10)H-5-one. On the cryptoanionic mechanism of N-substitution

Quantum chemical methods involving studies of transition states of the reaction showed that the main products of N-alkylation of prototropic 2,3-dihydroimidazo[2,1-b]quinazolin-1(10)H-5-one (1) in the gas phase and under neutral conditions in solution occurring via the S_N2 mechanism should be N(10)-alkyl-substituted derivatives formed from the 1H-tautomer. Minor N(1)-substituted derivatives in solution can be produced from both tautomers. For the alkylation of the free N-anion of compound 1, position 1 is attacked first. Validity of conclusions concerning the overall regioselectivity of the reaction was confirmed experimentally. In the absence of solvent, the alkylation proceeds abnormally with a sharp increase in the content of the 1-substituted isomers up to inversion of the regioselectivity of the reaction, which is explained by the participation in the process of the H-bonded dimer of the substrate (1a)₂, which undergoes alkylation via the cryptoanionic mechanism. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 876–887, May, 2006.     

Simple, expedient methods for the determination of water and electrolyte contents of cellulose solvent systems

The concentrations of water, W, and electrolytes present in solutions of LiCl in N,N-dimethylacetamide, LiCl/DMAc, and of tetrabutylammonium fluoride. x-hydrate in DMSO, TBAF.xW/DMSO can be accurately and expediently determined by three independent methods, UV–vis, FTIR and EMF measurement. The first relies on the use of solvatochromic probes whose spectra are sensitive to solution composition. It is applicable to W/LiCl/DMAc solutions but not to TBAF.xW/DMSO, because the charge-transfer complex bands of the probes are suppressed by strong interactions with the latter electrolyte. Integration of ν_OH band of water may be employed in order to determine [W], hence [electrolyte] by weight difference. EMF measurement uses ion-selective electrodes in order to determine [electrolyte], hence [W] by weight difference. Results of the latter method were in excellent agreement with those of FTIR. The reason for the failure of Karl Fischer titration is addressed, and the relevance of the results obtained to functionalization of cellulose under homogenous solution conditions is briefly commented on.     

Synthesis of pyrido[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidin-7(8<Emphasis Type="Italic">H</Emphasis>)-one derivatives from 5-acetyl-4-aminopyrimidines and β-dicarbonyl compounds

Heating of 5-acetyl-4-aminopyrimidine derivatives with ethyl acetoacetate, ethyl benzoylacetate, and diethyl acetone-1, 3-dicarboxylate in the absence of a base gave the corresponding 6-acylpyrido[2, 3-d]pyrimidin-7(8H)-ones. Under analogous conditions, the reaction with ethyl malonate afforded ethyl 7-oxo-7, 8-dihydropyrido[2, 3-d]pyrimidine-6-carboxylates. The pyridone (rather than hydroxypyridine) structures of the pyridopyrimidines obtained were confirmed by IR spectroscopy.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 770–773, March, 2005.     

离子交换色谱-基质辅助激光解吸电离串联飞行时间质谱分离鉴定中国人乳中的β-酪蛋白

以新鲜中国人乳为研究对象,在酸性条件下加氯化钙分离酪蛋白,用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)法测定分离效果。从pH值、离心力和CaCl2浓度等3个方面对分离效果进行评价。结果表明:当pH=4.3,离心力为10 400 g,CaCl2溶液浓度为60 mmol/L时,分离得到的酪蛋白组分纯度最高。对所得酪蛋白沉淀进行DEAE阴离子交换色谱分离,得到3个洗脱液。对其中第3个峰进行Western-Blot法及基质辅助激光解吸电离串联飞行时间质谱法(MALDI-TOF/TOF MS)鉴定,证明该峰能与人β-酪蛋白抗体特异性结合,确认其为人乳β-酪蛋白;将质谱结果在Mascot数据库中进行数据检索,序列覆盖率为50%,进一步确定其为人乳β-酪蛋白。综上所述,我们建立了能够得到符合蛋白质组学研究要求的人乳β-酪蛋白的方法。     

Synthesis of new pyrido[2,3-d]pyrimidine derivatives by three-component condensation of 5-acetyl-4-aminopyrimidines, cyclohexane-1,3-diones, and orthocarboxylic acid esters

A three-component condensation of 5-acetyl-4-aminopyrimidine derivatives with dimedone (or cyclohexane-1,3-dione) and triethyl orthoacetate (or triethyl orthopropionate) gave derivatives of 7-(1,3-dioxocyclohex-2-ylidene)-7,8-dihydropyrido[2,3-d]pyrimidine. These heterocyclic compounds containing the enamino ketone fragment can form boron chelates under the action of butoxy(diphenyl)borane. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2006–2011, November, 2006.     

Determination of thermodynamic functions of sorption for cyclohexyl-, piperidyl-, morpholyl-, and thiomorpholyl-n-alkanes by capillary gas-liquid chromatography

The values of partial molar free energy (G), enthalpy (H), and entropy (S) of sorption in the homologous series ofN-alkylpiperidines,N-alkylmorpholines,N-alkyl thiomorpholines, and alkylcyclohexanes were determined. It was found that the free energy of sorption is determined to a greater extent by the enthalpy term than by the entropy one. The free energy of sorption of the first homolog decreases when then-alkyl chain is attached directly to the carbon atom of the cycle and increases in the case ofN-alkylsubstituted heterocycles. The influence of the heteroatom nature on intermolecular interactions of homologs with the nonpolar stationary phase was quantitatively estimated on the basis of thermodynamic data.Dead time necessary for calculation of the retention factor was determined by the retention of methane injected into the column simultaneously with the sample.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2030–2032, August, 1996.     

Synthesis and structure elucidation of oxidative coupling products of 2-hydroxy-1,4-naphthoquinones

2,3-Dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinones are the products of oxidative coupling of substituted 2-hydroxy-1,4-naphthoquinones (regardless of the presence of peri-hydroxy groups in their structures) under the action of lead dioxide. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 294—298, February, 2006.     

Analysis of steroids in yeast-mediated cell culture by on-line solid-phase extraction coupled high-performance liquid chromatography electrospray-ionization/mass spectrometry and novel continuous postcolumn infusion of internal standard technique

The reduction of 17-ketosteroid estrone or androstenedione to corresponding 17α- and 17β-estradiol or testosterone and epitestosterone has been performed with Saccharomyces cerevisiae. In the analysis of the cell culture, the solid-phase extraction (SPE) method was on-line coupled to high-performance liquid chromatography electrospray-ionization/mass spectrometry (HPLC-ESI/MS) for sample pretreatment to eliminate the complicated matrix interference and preconcentrate of the analytes before chromatographic separation. A novel quantification method with the continuous postcolumn infusion of internal standard was developed for the determination of substrate and products. This novel quantitative method can stabilize and enhance the ionization of all analytes during analysis. The HPLC-ESI/MS analysis of estrone, 17α-, and 17β-estradiol was operated with a negative ion mode and the analysis of androstenedione, testosterone, and epitestosterone was operated with a positive ion mode. The optimal concentration of the internal standard progesterone with the continuous postcolumn infusion technique was 3 μg mL⁻¹ for estrogen analysis and 1 ng mL⁻¹ for androgen analysis and both were at a constant infusion rate of 0.5 μL min⁻¹. All of the linear correlation coefficients of the standard calibration curves were over 0.99 and had a linear range from 0 to 50 ng mL⁻¹. The limit of detections (LODs) and the limit of quantitations (LOQs) for steroids analyzed were from 0.12 to 0.36 ng mL⁻¹ and from 0.4 to 1.2 ng mL⁻¹, respectively. The analysis accuracies and precisions were better than 94% and lower than 8.8% R.S.D., respectively. The developed method for the analysis of steroids in the cell culture was successful.     

Some theoretical and practical aspects in the separation of humic substances by combined liquid chromatography methods

Permanent need to understand nature, structure and properties of humic substances influences also separation methods that are in a wide scope used for fractionation, characterization and analysis of humic substances (HS). At the first glance techniques based on size-exclusion phenomena are the most useful and utilized for relating elution data to the molecular mass distribution of HS, however, with some limitations and exceptions, respectively, in the structural investigation of HS. The second most abundant separation mechanism is reversed-phase based on weak hydrophobic interactions beneficially combined with the step gradients inducing distinct features in rather featureless analytical signal of HS. Relatively great effort is invested to the developments of immobilized-metal affinity chromatography mimicking chelate-forming properties of HS as ligands in the environment. Surprisingly, relatively less attention is given to the ion-ion interactions based ion-exchange chromatography of HS. Chromatographic separation methods play also an important role in the examination of interactions of HS with pesticides. They allow us to determine binding constants and the other data necessary to predict the mobility of chemical pollutants in the environment. HS is frequently adversely acting in analytical procedures as interfering substance, so more detailed information is desired on manifestation of its numerous properties in analytical procedures. The article topic is covered by the review emphasizing advances in the field done in the period of last 10 years from 2000 till 2010.     

Pesticides in water and the performance of the liquid-phase microextraction based techniques. A review

The control of pesticides in surface, drinking and groundwater is nowadays a real necessity. In the European Community, their concentration must comply with the established parametric and environmental quality standards (EQSs). Regarding the new legislation, this article updates the information concerning the monitoring of pesticides and the technical specifications for their measurement in water samples where ultra-sensitive analytical methods are required. For some compounds, like pesticides, there is still a need to improve the performance of the existing methods. High sensitive techniques like gas chromatography tandem mass spectrometry (GC–MS/MS) and liquid chromatography coupled with mass spectrometry (LC–MS) have been developed. However, for most of the substances present at trace and ultra-trace levels the extraction and preconcentration steps are so far essential for their detection. Advances at a micro scale have been made and different types of microextractions are being developed. Liquid-phase microextraction (LPME) is an example. The study of this technique has increased in the last years and some innovations have been recently reported for pesticides water analysis. This article reviews the new developed LPME-based techniques and compares its performance with the analytical specifications established for pesticides water monitoring. The results show that LPME-based techniques can be a promising tool to improve the nowadays performance of methods used in pesticides water control.