Phosphorimetric assay for β-glucuronidase in biological materials

A highly sensitive phosphorimetric method for the assay of β-glucuronidase in biological samples is described. p-Nitrophenol, formed enzymatically from p-nitrophenyl β-D-glucuronide, is extracted with ether and determined phosphorimetrically in a mixture of ether and ethanolic potassium hydroxide. The method is rapid, precise, and very sensitive, requiring as little as 0.5–5 μl of human serum or urine, or 0.3–3.0 μg of protein of rat tissue. The limit of detection for the p-nitrophenol formed is 20 pmol.     

An ultramicro assay for human plasma prekallikrein activity by phosphorimetry

A highly sensitive method for the phosphorimetric assay of prekallikrein in human blood plasma is described. Prekallikrein is converted to kallikrein (active form) by reaction at 0°C with actin. p-Nitroaniline, formed enzymatically from H-d-prolyl-l-phenylalanyl-l-arginyl-p-nitroanilide, is extracted with ether and determined phosphorimetrically in a mixture of ether and ethanol. The method is precise and highly sensitive, requiring as little as 0.25 μl of human blood plasma. The limit of detection for p-nitroaniline formed enzymatically is 5 pmol.     

Chemoselective ester/ether C–O cleavage of methyl anisates by aluminum triiodide

The aluminum triiodide mediated chemoselective ester/ether C–O cleavage of methyl anisates was investigated. o-Anisate undergoes ether cleavage at low temperatures in carbon disulfide, cyclohexane and acetonitrile. Further cleavage of the ester group occurs at elevated temperatures to afford salicylic acid. The cleavage of p-anisate is solvent-dependent. In cyclohexane, the ester and ether groups were cleaved non-selectively to give equimolar amounts of p-anisic acid and methyl p-hydroxybenzoate. The ester group was preferentially cleaved in acetonitrile, compared to ether group cleavage in carbon disulfide. The ester cleavage reaction was improved using pyridine as an acid scavenger additive. Reasons for the contrasting reactivity of anisates towards AlI₃ were explored, and the methods were applied to cleavage of the tert-butyl ester of acemetacin which gave different products under these conditions.     

Determination of phosphatidylcitoline in serum with use of a choline-sensitive membrane electrode

A choline-sensitive membrane electrode made with potassium tetrakis(p-chlorophenyl) borate as the exchanger and o-nitrophenyl phenyl ether as membrane solvent in poly (vinyl chloride) was almost insensitive to the surfactant sodium deoxycholate. By using this electrode, choline ( 10^?5 M) formed by the enzymatic hydrolysis of phosphatidylcholine with phospholipase D in the presence of sodium deoxycholate as activator was successfully measured. The method was applied to the determination of phosphatidylcholine in serum.     

The synthesis and analytical capabilities of chromogenic aza-12-crown-4 as a selective reagent for lithium ion

The synthesis and analytical capabilities of a new chromogenic crown ether, 1-(2-hydroxy-5-nitrobenzyl)-1-aza-4,7,10-trioxacyclododecane, chromogenic aza-12-crown-4. Constants found for this aza-12-crown-4 were pK_a1 = 5.77, pK_a2 = 10.31, pK_ex (Li) = 10.18, and pK_ex (Na) = 12.50. The calibration curve obtained for the extraction-spectrophotometric procedure was linear from 0.3 to 2 μg ml^?1. The imprecision of the measurement was calculated from the mean value of the standard deviations of triplicate samples over the linear range and was less than 5%. Results for the determination of lithium in blood serum and urine exhibited good agreement with atomic absorption data.     

Biparametric multicommutated flow analysis system for determination of human serum phosphoesterase activity

A multicommutated flow analysis (MCFA) system constructed of microsolenoid valves and pumps offering simultaneous determination of activity of acid phosphatase (ACP) and alkaline phosphatase (ALP) in human serum samples has been developed. The MCFA system is based on optoelectronic flow-through detector made of two light emitting diodes and operating according to paired emitter detector diode (PEDD) principle. This photometric PEDD device has been dedicated for detection of p-nitrophenol (NP) generated in the course of enzymatic hydrolysis of p-nitrophenyl phosphate and optimized for the determination of NP in human serum samples. The developed PEDD-based MCFA system allows independent optimization of conditions for reaction and detection steps of photometric ACP and ALP bioassays. Moreover, it allows elimination of photometric interferences from serum matrix components according to two-points kinetic mode of measurement. The single measurement cycle takes 12 min, consists of four measurements (two for each phosphoesterase) and enables determination of serum ACP and ALP activities at physiological and pathological levels. The real analytical utility of the developed MCFA system has been confirmed by analysis of control sera as well as real human serum samples from healthy persons and oncological patients.     

Synthesis,including asymmetric synthesis,of 3-oxabicyclo[3.1.0]hexanes and bicyclo[3.1.0]hexanes by the 1,5-CH insertion of cyclopropylmagnesium carbenoids as the key reaction

The addition reactions of α,β-unsaturated carbonyl compounds with dichloromethyl p-tolyl sulfoxide in the presence of NaHMDS or LDA resulted in the formation of adducts, 1-chlorocyclopropyl p-tolyl sulfoxides bearing a carbonyl group at the 2-position, in almost quantitative yields. The carbonyl group of the adducts was transformed to various ether groups to give 1-chlorocyclopropyl p-tolyl sulfoxides bearing an ether functional group at the 2-position in short steps. Treatment of these products with i-PrMgCl at low temperature afforded cyclopropylmagnesium carbenoids via the sulfoxide-magnesium exchange reaction. 1,5-Carbon–hydrogen insertion (1,5-CH insertion) reaction of the generated magnesium carbenoid intermediates took place to give 3-oxabicyclo[3.1.0]hexanes or bicyclo[3.1.0]hexanes bearing an ether group at the 4-position in moderate to good yields. When this procedure was carried out starting with enantiopure dichloromethyl p-tolyl sulfoxide, enantiopure 3-oxabicyclo[3.1.0]hexanes were obtained in good overall yields. These procedures provide a good way for the synthesis, including asymmetric synthesis, of multisubstituted 3-oxabicyclo[3.1.0]hexanes and bicyclo[3.1.0]hexanes from α,β-unsaturated carbonyl compounds and dichloromethyl p-tolyl sulfoxide in short steps.     

A one-pot four-component synthesis of N-arylidene-2-aryl-imidazo[1,2-a]azin-3-amines

N-Arylidene-2-aryl-imidazo[1,2-a]azin-3-amines were synthesized via a one-pot, four-component condensation reaction using a 2-aminoazine, toluene-4-sulfonylmethyl isocyanide (TsCH₂NC), and two equivalents of readily available aromatic aldehydes. The reaction was performed in diethyl ether as the solvent, with p-toluenesulfonic acid (p-TSA) as the catalyst at reflux temperature.     

Interfacial behavior of phase transfer catalysis of the reaction between potassium thiocyanate and p-nitrobenzyl bromide with crown ethers as catalysts

A very simple and novel method is devised to study the mechanism of phase transfer catalysis (PTC) for a nucleophilic substitution reaction between potassium thiocyanate and p-nitrobenzyl bromide (p-NB); the mechanism of the nucleophilic substitution reaction is illustrated by characterizing the interfacial dilational viscoelastic properties of the crown ether catalysts and intermediates, which are closely related to the interfacial behavior of the species in the PTC reaction. The results obtained from this study can be used to infer the mechanism of the nucleophilic substitution reaction that uses 18-crown-6 (18C6) and dibenzo-18-crown-6 (DB18C6) as phase transfer catalysts. This mechanism begins with formation of the intermediates [K · Crown ether]⁺ and [K · Crown ether]⁺SCN^? through mutual collisions between crown ethers and KSCN in the aqueous phase near the interface. Then the complex, [K · Crown ether]⁺Br^?, was obtained due to the collision between [K · Crown ether]⁺SCN^? and p-NB in the organic phase near the interface and simultaneously the products were obtained.     

Metal-free synthesis of reactive oligomers by ring-opening oligomerization of glycidyl phenyl ether initiated with tetra-n-butylammonium fluoride in the presence of various protic compounds

Metal-free ring-opening oligomerizations of glycidyl phenyl ether (GPE) were performed with tetra-n-butylammonium fluoride (n-Bu₄NF) as an initiator in the presence of protic compounds (RHs) as chain transfer agents (CTAs). The RHs having pKa between 4.66 and 15.5 enabled to serve as the CTA in this oligomerization system, leading to reactive oligomers with relatively controlled molecular weights having narrow molecular weight distributions bearing functional groups such as alkene, benzyl ether, alkyne, ester and methacrylate groups at initiating end.     

Elaboration of the ether cleaving ability and selectivity of the classical Pearlman's catalyst [Pd(OH)2/C]: concise synthesis of a precursor for a myo-inositol pyrophosphate

The cleavage of propargyl, allyl, benzyl, and PMB ethers by Pd(OH)₂/C can be tuned in that order, by varying the reaction conditions. Other moieties such as C-C double bonds, esters, trityl ether, p-bromo and p-nitrobenzyl ethers are stable to these reaction conditions. Cleavage of allyl ethers can be made catalytic by using 1:1 mixture of Pd(OH)₂/C and Pd/C. The synthetic potential of the selective ether cleaving ability of Pd(OH)₂/C, essentially under neutral conditions, has been demonstrated by an efficient synthesis of a precursor for the preparation of an inositol pyrophosphate derivative.     

Selective performance of sol-gel synthesised titanium dioxide photocatalysts in aqueous oxidation of various-type organic pollutants

Photocatalysts synthesized by sol-gel method inevitably incorporate carbon together with dopants. The objective of the research consists in the synthesis and testing of photocatalytic activity of carbon-containing titanium dioxide photocatalysts calcinated at various temperatures. The optical and structural properties of the catalysts were also studied. The activity was tested in visible light in aqueous photocatalytic oxidation of three various-type pollutants, methyl-tert-butyl ether, p-toluidine and phenol, where the divergent character of the C-TiO₂ catalysts was distinctively observed: methyl-tert-butyl ether and p-toluidine were oxidized with the efficiency close to or even surpassing that of UV-irradiated P25 (Evonik), whereas phenol was oxidized poorly. The observed photocatalytic activity, where quantum efficiency varied from 0.6 to 2.3 and from 0.1 to 1.2% for p-toluidine and phenol degradation respectively, may be explained by the different electrostatic properties of the catalysts’ surface and the tested substances, i.e. their interaction. This compromises the widespread usage of phenol as a reference substance for comparison of catalytic activities of catalysts.     

Structure of ethyl 3-(4-tolyl)hydrazono-2,4-dioxopentanoates

As a result of one-pot three-component condensation of acetone with diethyl oxalate and p-tolyl diazonium chloride of ethyl 3-(4-tolyl)hydrazono-2,4-dioxopentanoates p-tolyl diazonium diethyloxalate and chloride, ethyl ether of 3-(4-tolyl)hydrazono-2,4-dioxopentanoic acid is obtained. The structure of the synthesized compound is studied.     

Determination of betaines as ultraviolet-absorbing esters

A method is described for the estimation of fully N-methylated amino acids (betaines) in plant extracts. After partial purification of aqueous extracts with ion-exchange resins, a crown ether and potassium phosphate buffer are used to facilitate the esterification of betaines with α, p-dibromoacetophenone, p-nitrobenzyl bromide or α-bromo-p-tolunitrile. The esters are isolated with dilute sulphuric acid and chloroform; 10–200 nmol can be determined spectrophotometrically, and smaller amounts by high-performance liquid chromatography.     

Aniline–terephthalaldehyde resin p-toluenesulfonic acid (ATRT) salt as efficient mild polymeric solid acid catalyst

Aniline–terephthalaldehyde resin p-toluenesulfonic acid (ATRT) salt was easily prepared by the reaction of aniline with 1.25 equiv of terephthalaldehyde in the presence of 1.0 equiv of p-toluenesulfonic acid at 75 °C for 24 h in EtOH. ATRT efficiently catalyzed the tetrahydropyranylation of alcohols and deprotection of tetrahydropyranyl (THP), triethylsilyl (TES), and tert-butyldimethylsilyl (TBDMS) ethers. Deprotection of dodecyl THP ether and dodecyl TBDMS ether catalyzed by ATRT proceeded faster than those by pyridinium p-toluenesulfonate (PPTS). ATRT was reused without significant loss of activities.     

Synthesis and characterization of a novel polyazomethine ether for NLO application

Polymer containing azomethine and ether linking groups between phenylene rings has been prepared. It is a polycondensation reaction of a single monomer containing nitro as well as hydroxyl group in p,p^′ position from 4-nitroaniline and 4-hydroxy benzaldehyde. The polymer has been characterized by elemental analysis, IR, UV and NMR spectroscopies, viscometry and thermal studies. The thermotropic liquid crystalline behaviour of the polymer is investigated by optical polarizing microscopy. The crystalline behaviour of the polymer is confirmed by XRD study. The polymer shows good second harmonic generation for non-linear optical application.     

A versatile synthesis, including asymmetric synthesis, of bicyclo[n.1.0]alkanes from cyclic ketones via the magnesium carbenoid 1,3-CH insertion as a key reaction

Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from various cyclic ketones and chloromethyl p-tolyl sulfoxide in three steps, in high yields, with lithium enolate of tert-butyl acetate or its homologues gave the adducts in quantitative yields. The adducts were treated with isopropylmagnesium chloride in ether in dry toluene as the reaction solvent to afford bicyclo[n.1.0]alkanes in high to quantitative yields via magnesium carbenoid 1,3-CH insertion. When this method was carried out starting from unsymmetrical cyclic ketones and (R)-chloromethyl p-tolyl sulfoxide, an asymmetric synthesis of bicyclo[n.1.0]alkane was realized.     

The relationship between the association constants of phenol with ethers and those of tricholoroacetic acid with ethers : Estimation of association constants of trichloroacetic acid with oxirane

The association constants, K_p, of phenol with ethers (tetrahydrofuran, tetrahydropyran dibutyl ether, dipropyl ether, 1,4-dioxane) and those , K_T, of trichloroacetic acid with ethers were measured in CCl₄ over a temparature range 20°–40° using near IR spectra. A linear relationship between K_p and K_T was found. On the basis of this realtionship the association constants of trichloroacetic acid with propylene oxide were estimated from those of phenol with propylene oxide.     

Fluorescent investigation of the interactions between N-(p-chlorophenyl)-N'-(1-naphthyl) thiourea and serum albumin: synchronous fluorescence determination of serum albumin

The interactions between N-(p-chlorophenyl)-N′-(1-naphthyl) thiourea and serum albumin were investigated by fluorescence spectroscopy and UV absorption spectrum under physiological conditions. The results of spectroscopic measurements suggested that N-(p-chlorophenyl)-N′-(1-naphthyl) thiourea should have a strong ability to quench the intrinsic fluorescence of both bovine serum albumin and human serum albumin through static quenching procedure, and the hydrophobic interaction was the predominant intermolecular force stabilizing the complex. Thermodynamic parameter enthalpy changes (ΔH) and entropy changes (ΔS) were calculated according to the Vant’Hoff equation. The binding distances between N-(p-chlorophenyl)-N′-(1-naphthyl) thiourea and the proteins were evaluated on the basis of the theory of Föster energy transfer. In addition, the effects of other ions on the binding constants of complexes were also discussed. Synchronous fluorescence technology was successfully applied to the determination of serum albumins added to the CPNT solution.     

Thermal polycondensation of hexa-p-hydroxymethylphenoxycyclotriphosphazene

A procedure for the synthesis of hexa-p-hydroxymethylphenoxycyclotriphosphazene is optimized. The thermal characteristics of this compound are studied, and its capability for thermal self-con-densation is demonstrated. The main steps of polycondensation of hexa-p-hydroxymethylphenoxycyclotriphosphazene involve the formation of methylene ether bonds accompanied by the evolution of water and their further scission without formation of formaldehyde. The resulting polymer is thermally stable up to 470°C.