Hydroxamic acids as colorimetric reagents

Thirty-three hydroxamic acids and three N-substituted hydroxamic acids or structurally similar compounds have been studied as possible colorimetric reagents for metal ions. They were tested with 78 ions under varying conditions of acidity and basicity. Aliphatic, substituted aliphatic, aromatic, substituted aromatic, and heterocyclic hydroxamic acids were represented in the compounds studied. An attempt was made to correlate the activity towards metal ions with variations in the molecular structure of the hydroxamic acids. The studies with C-substituted hydroxamic acids indicate that the preferential formation of a colour or a precipitate depends on pH, the solvent, and reagent concentration, and is not a function of the presence or absence of a substituent on the nitrogen atom. A number of the compounds offer promise of being useful colorimetric reagents under proper reaction conditions.     

Relation between chemical structure of amino acids and their thermal decomposition

The influence of substituents on the thermal decomposition of monomeric organic compounds was studied. For this purpose the thermal destruction of dozen or so α-amino acids of the diversified chemical constitution, among others compounds containing the second amine group, additional carboxyl group, amino acids containing hydroxyl or sulfhydryl groups and amino acids connected with five-member heterocyclic ring or existing in the form of hydrates or hydrochlorides were investigated. The analyses were performed using a derivatograph in an air atmosphere, sample sizes were from 50 to 200 mg and heating rate from 3 to 15 K min^-1. It has been established that the thermal decomposition of studied compounds occurs in three stages. The temperature ranges, in which the analyzed compounds undergo thermal transformations were established. For evaluation of the thermoanalytical results an advanced multivariate data processing method, principal component analysis (PCA), was used. By this method the influence of the specific functional groups on the thermal decomposition of α-amino acids was determined. The stage of decomposition, in which the thermoanalytic data are the best correlated to the chemical constitution of the compound, is the second stage. It has also been recognized, that better discrimination among the analyzed compounds was obtained for the data set of the DTA.     

Synthesis and properties of new types of sulfoxide‐ or sulfone‐bridged lewis acids

A series of new types of sulfur‐bridged Lewis acids were synthesized. The ligands that contained the sulfoxide or sulfone as the joint moieties of two phenols were found to quantitatively give Lewis acids. These obtained Lewis acids also have good discrimination properties of some epoxides. The reaction prop erties of the Lewis acids were studied using the rearrangement of the epoxides to carbonyl compounds.     

Synthesis of imidazolino [1,2-f]xanthin-2-ones and their methylene-group-substituted derivatives

8-Amino-7-theophyllylacetic acids and their esters were obtained by reaction of 8-amino(alkylamino, arylamino)theophyllines with haloacetic acids and their esters. The structures of the products were established, and the conditions for cyclization to imidazolino[1,2-f]xanthin-2-one derivatives were studied. The corresponding methylene-group-substituted derivatives were synthesized by reaction of the imidazolino[1,2-f]xanthin-2-one derivatives with aldehydes, isatin, aromatic nitroso compounds, and arenediazonium salts. The ylidene derivatives of this threering system were also obtained by reaction of 8-amino-7-theophyllylacetic acids or their esters with carbonyl compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1132–1135, August, 1976.     

Docking studies and anti-inflammatory activity of beta-hydroxy-beta-arylpropanoic acids

The article describes a two-step synthesis of diastereomeric 3-hydroxy-2-methyl-3-(4-biphenylyl)butanoic acids. In the first step an intermediate alpha-bromo propanoic acid 1-ethoxyethyl ester was synthesized. The second step is a new modified Reformatsky reaction in presence of Zn in tetrahydrofuran (THF) at -5 to 10 degrees C between the previously synthesized intermediate and 4-acetylbiphenyl. Synthesis of the other studied beta-hydroxy-beta-arylpropanoic acids has already been reported. These beta-hydroxy-beta-arylpropanoic acids belong to the arylpropanoic acid class of compounds, structurally similar to the NSAIDs such as ibuprofen. The anti-inflammatory activity and gastric tolerability of the synthesized compounds were evaluated. Molecular docking experiments were carried out to identify potential COX-2 inhibitors among the beta-hydroxy-beta-aryl-alkanoic acids class. The results indicate that all compounds possess significant anti-inflammatory activity after oral administration and that the compounds 2-(9-(9-hydroxy-fluorenyl))-2-methylpropanoic acid (5) and 3-hydroxy-3,3-diphenyl-propanoic acid (3) possess the strongest anti-inflammatory activity, comparable to that of ibuprofen, a standard NSAID,and that none of tested substances or ibuprofen produced any significant gastric lesions.     

Separation of some amino acids by supercritical fluid chromatography after a pre-derivatization step with classical reagents

Summary The separation of polar compounds by supercritical fluid chromatography is a difficult problem to solve. In this work, we have used a pre-derivatization method to obtain apolar or less polar compounds. Amino acids have been chosen as model polar compounds of biological interest, and 9-fluorenylmethyl chloroformate (FMOC) and (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC) have been used as derivatizating reagents.With this procedure, the amino acids studied have been separated in less than 40 minutes with a good efficiency. Furthermore, with FLEC reagent, the enantiomeric separation was rapid in comparison with liquid chromatography techniques and the selectivities obtained were in the same order of magnitude.     

杂多酸(盐)及单缺位磷钨杂多化合物在醇类氧化反应中的催化活性

在相转移条件下,研究了杂多化合物在苄醇,环己醇氧化反应中的催化活性.六种Keggin结构杂多酸的催化活性按GeMo~12(H~4GeMo~12O~40的简写,其余类推,PW~12,PMo~12,SiMo~12,GeW~12,SiW~12顺序下降,杂多酸中的质子可分别被其它阳离逐渐取代而达到酸性修饰. H~3PW~12O~40随着其质子逐步被Na^+取代,酸性下降,催化活性大大提高;杂多酸(盐)的催化活性随体系pH值的改变将发生奇妙剧烈的变化;单缺位杂多化合物显示出较饱和杂多酸(盐)更高催化活性.溶剂对催化活性有明显影响.     

Structure and spectra of diazotized o-aminonaphthols and their isomeric monosulfonic derivatives

The structure and behavior of o-naphthoquinonediazides and their monosulfonic acids in media of different acidity were studied by means of UV and IR spectra. In neutral, weakly acid and weakly alkaline solutions the diazo compounds of 1,2- and 2,1- aminonaphthols and their sulfonic acids exist in equilibrium as the diazonium and quinonediazide forms. The sulfonic acids, and also their metal salts, possess an ionic structure; the sulfonyl chlorides of the quinonediazides are not ionized. It was shown that of the two extreme equilibrium forms of the diazo compounds the quinone diazide was the more photosensitive. The nature of the phototransformation products of 2,1-naphthoquinonediazide depends to a considerable degree on the medium which causes a shift into one or the other of the diazo forms.     

Preparation of chitosan functionalized monolithic silica column for hydrophilic interaction liquid chromatography

A novel cationic hydrophilic interaction monolithic stationary phase based on the chemical modification of carboxymethyl chitosan (CMCH) to the monolithic silica skeleton using carbodiimide as an activation reagent was prepared for performing capillary liquid chromatography. The amino and hydroxy moieties of CMCH functioned as both the ion-exchange sites and polar providers. The performance of the column was studied by the separation of polar acidic compounds. The chitosan functionalized monolithic silica column showed good selectivity for nucleosides, nucleotides, aromatic acids and aliphatic acids. The mechanism for the separation of these compounds was also studied. The results showed that these compounds were separated primarily based on the hydrophilic interaction mechanism.     

Composition of the black crusts from the Saint Denis Basilica, France, as revealed by gas chromatography-mass spectrometry

The organic fraction of black crusts from Saint Denis Basilica, France, is composed of a complex mixture of aliphatic and aromatic compounds. These compounds were studied by two different analytical approaches: tetramethyl ammonium hydroxide (TMAH) thermochemolysis in combination with gas chromatography-mass spectrometry (GC-MS), and solvent extraction, fractionation by silica column, and identification of the fraction components by GC-MS. The first approach, feasible at the microscale level, is able to supply fairly general information on a wide range of compounds. Using the second approach, we were able to separate the complex mixture of compounds into four fractions, enabling a better identification of the extractable compounds. These compounds belong to different classes: aliphatic hydrocarbons (nalkanes, n-alkenes), aliphatic and aromatic carboxylic acids (n-fatty acids, alpha,omega-dicarboxylic acids, and benzenecarboxylic acids), polycyclic aromatic hydrocarbons (PAH), and molecular biomarkers (isoprenoid hydrocarbons, diterpenoids, and triterpenoids). With each approach, similar classes of compounds were identified, although TMAH thermochemolysis failed to identify compounds present at low concentrations in black crusts. The two proposed methodological approaches are complementary, particularly in the study of polar fractions.     

Fulvic acid enrichment in the microlayer of the Gerlache Inlet Sea (Antarctica): preliminary results

The aim of this work was to study the presence of fulvic acids in Antarctic waters, as they appear to be principal film-forming components in the surface microlayer. We obtained a series of samples during two Antarctic Italian Expeditions in 1998/99 and 2000/01 and studied the distribution and the structural differences between fulvic acids extracted from both microlayer and subsurface waters.

Fulvic acids are concentrated in the microlayer and the enrichment factor between microlayer and subsurface water differs between samples. The enrichment factor values for fulvic acids lie between those found for dissolved organic carbon (DOC) and particulate organic carbon (POC) in the literature. Fulvic acids extracted from the microlayer were found to be different in structure from those present in the subsurface layer and enriched in sulphur content. We hypothesised that sulphur-containing compounds are slightly bound and/or occluded in fulvic acid structures. The sulphur-containing compounds analysed in the microlayer could be dimethylsulfide (DMS) and/or its products stemming from photochemical and biological oxidation reactions.     

Effect of pH on inhibition and enhancement of luminol-H2O2-Co2+ chemiluminescence by phenolic compounds and amino acids

The effect of pH on inhibition and enhancement of luminol-H2O2-Co2+ chemiluminescence (CL) by 18 phenolic compounds and 20 amino acids was studied. It was found that most of the tested compounds showed an inhibiting effect at lower pH and an enhancing effect at higher pH. At a midrange pH, for some phenolic compounds with two ortho-position -OH, both an inhibiting and an enhancing peak were simultaneously observed. UV-visible spectra of the tested phenolic compounds at different pH values were studied. The mechanism for CL inhibition and enhancement was proposed. It is likely that the competition of the -OH or the -NH2 group and other reducing groups in the molecules with luminol for O2*- led to the CL inhibition. A reaction of -COO(-) and quinone or ketone formed by phenolic compounds at higher pH via deprotonation with O2*- also resulted in the CL enhancement.     

三(2-甲基-2-苯基丙基)锡芳氧乙酸酯的合成

三（２－甲基－２－苯基丙基）锡芳氧乙酸酯的合成刘宝殿,宁志刚,朱东升,包明（东北师范大学化学系,长春,１３００２４）关键词三（２－甲基－２－苯基丙基）锡芳氧乙酸酯,三（２－甲基－２－苯基丙基）氢氧化锡,芳氧乙酸,杀螨活性１９６６年Ｒｅｉｃｈｌｅ［１］...     

Liquid chromatographic/electrospray ionization tandem mass spectrometric study of the phenolic composition of cocoa (Theobroma cacao)

Liquid chromatography coupled with ionspray mass spectrometry in the tandem mode (LC/MS/MS) with negative ion detection was used for the identification of a variety of phenolic compounds in a cocoa sample. Gradient elution with water and acetonitrile, both containing 0.1% HCOOH, was used. Standard solutions of 31 phenolic compounds, including benzoic and cinnamic acids and flavonoid compounds, were studied in the negative ion mode using MS/MS product ion scans. At low collisional activation, the deprotonated molecule [M - H](-) was observed for all the compounds studied. For cinnamic and benzoic acids, losses of CO(2) or formation of [M - CH(3)](-*) in the case of methoxylated compounds were observed. However, for flavonol and flavone glycosides, the spectra present both the deprotonated molecule [M - H](-) of the glycoside and the ion corresponding to the deprotonated aglycone [A - H](-). The latter ion is formed by loss of the rhamnose, glucose, galactose or arabinose residue from the glycosides. Different fragmentation patterns were observed in MS/MS experiments for flavone-C-glycosides which showed fragmentation in the sugar part. Fragmentation of aglycones provided characteristic ions for each family of flavonoids. The optimum LC/MS/MS conditions were applied to the characterization of a cocoa sample that had been subjected to an extraction/clean-up procedure which involved chromatography on Sephadex LH20 and thin-layer chromatographic monitoring. In addition to compounds described in the literature, such as epicatechin and catechin, quercetin, isoquercitrin (quercetin-3-O-glucoside) and quercetin-3-O-arabinose, other compounds were identified for the first time in cocoa samples, such as hyperoside (quercetin-3-O-galactoside), naringenin, luteolin, apigenin and some O-glucosides and C-glucosides of these compounds.     

大气光化学反应研究（Ⅱ）—二氧化硫与异戊烷的光化学反应

研究了SO_2与异戊烷在无氧和有氧体系中的光化学反应,用GC和GC-MS法确证了部分气、液相产物,包括醇、醛、酮、酯和烃类及含硫有机物,探讨了影响光化学反应的因素和反应机理.     

三苯基锡芳氧乙酸酯的合成和表征

三苯基锡芳氧乙酸酯的合成和表征刘宝殿，包明，张景萍（东北师范大学化学系、东北师范大学分析测试中心，长春，１３００２４）关键词芳氧乙酸，三苯基锡芳氧乙酸酯，合成，生物活性三苯基醋酸锡和三苯基氢氧化锡是防治甜菜褐斑病的有效药剂［１］．芳氧乙酸及其酯也具有...     

Extraction of scandium ions by new aminophosphinyl extractants

Extraction of Sc(III) ions by new aminophosphinyl compounds containing one or two methylenediorganylphosphinyl groups at the nitrogen atom was studied with a target of the development of effective and selective extractants of trace elements. The selection of extractants was due to their high hydrolytic stability in the acid media, commonly used at the extraction of metal ions in the industrial hydrometallurgical processes. The study of extraction of hydrogen chloride and nitric acids with the selected aminophosphinyl compounds allowed a discovery of substances with the low basicity, which were characterized by the low coefficient of the acids extraction. Highly effective extractants of Sc(III) were found possessing high coefficients of extraction and high degree of selectivity in the separation of Sc(III) ion from the ions of satellite metals.     

Synthesis of the novel β-aminophosphoryl compounds and their acid-base properties and membrane-transport abilities towards carboxylic acids

The highly efficient synthesis of β-aminophosphoryl compounds with one and two ethylphosphoryl groups was performed by the addition of amines to the vinylphosphoryl compounds in water as a solvent. The acid-base properties and membrane-transport abilities of the target compounds towards carboxylic acids were studied. Selectivity towards acetic acid was revealed.     

Features of switchable multicomponent heterocyclizations of salicylic aldehydes and 5-aminopyrazoles with pyruvic acids and antimicrobial activity of the reaction products

Three-component reactions of 5-aminopyrazoles and salicylic aldehydes with pyruvic acids were studied. The method of tuning of the selectivity of the heterocyclizations allowing to change its direction by variation of the reaction parameters was worked out. The treatment involving pyruvic acid can be selectively directed to the formation to either 3-aryl-10,11-dihydro-4,10-methano-pyrazolo[4,3-c][1,5]benzoxazocine-4-carboxylic acids or 3,6-diarylpyrazolo[3,4-b]pyridine-4-carboxylic acids, while the reaction involving arylpyruvic acid leads only to 7-hydroxy-2,5,6-triaryl-4,5,6,7-tetrahydro-pyrazolo[1,5-a]pyrimidine-7-carboxylic acids. Antimicrobial activity of the compounds obtained was also studied: Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) were found sensitive to the substances tested, however, only in the highest concentration.     

Understanding of rifamycin S. Reactions of the ansa-rings. Modifications of antibiotics. 8

The reactivity of rifamycin-S with respect to acids, bases, and oxydizing or reducing agents has been studied. A number of compounds resulting from these experiments as well as derivatives of rifamycin-S resulting from acylation and ketalisation reactions are described.