Acridinium ester chemiluminescence: pH dependent hydrolysis of reagents and flow injection analysis of hydrogen peroxide and glutamate

An automated analysis system is described for the measurement of hydrogen peroxide based on a chemiluminescence reaction with phenyl 10-methylacridinium-9-carboxylate (PMAC). A reversed FIA experimental arrangement is used to establish the operating conditions for the measurement of submicromolar levels of hydrogen peroxide. The carrier stream consists of hydrogen peroxide standards prepared in a pH 9.0, boric acid buffer and the flow rate for this carrier/sample stream is 4 ml/min. Twenty microliters of a 10 mM PMAC solution, prepared in a pH 3 phosphate buffer, are injected into the carrier/sample stream. Hydrogen peroxide mixes with the PMAC reagent in an incubation coil that is constructed by wrapping 107 cm of polyethylene tubing around a 1 cm o.d. plastic rod. The chemiluminescence reaction is then initiated by adding base just before the sample passes in front of a photomultiplier tube (PMT) detector. The calculated limit of detection (S/N = 3) for hydrogen peroxide is 0.25 M. In addition, the pH dependent hydrolysis of the PMAC reagent is characterized by an HPLC method which has been specifically developed for the separation and detection of the hydrolysis products of PMAC. Results indicate that a pH of 3.0 is required for long term stability of the PMAC reagent. Finally, this system has been successfully extended to the measurement of glutamate by coupling a bioreactor column of glutamate oxidase with the hydrogen peroxide detection scheme. A detection limit (S/N = 3) of 0.5 M has been established for glutamate with a throughput of 200 samples per hour.     

Über Chalkogenolate. 206 [1]. N-Thioacetyldithiocarbamate und Ester der N-Thioacetyldithiocarbamidsäure

On Chalcogenolates. 206. N-Thioacetyl Dithiocarbamates and Esters of N-Thioacetyl Dithiocarbamic Acid Thioacetamide reacts with carbon disulfide in the presence of KH to form via the tetrabutyl ammonium salt dark yellow N-thioacetyl dithiocarbamates M[S₂C? NH? CS? CH₃], where M = K, Rb, Cs. The salts as well as the methyl and ethyl ester have been characterized by means of electron absorption, infrared, nuclear magnetic resonance (¹H and ¹³C), and mass spectra. Attempts to synthesize N-thioacetyl dithiocarbamic acid were not successful.     

Multivariate monitoring of soybean oil ethanolysis by FTIR

In this work, an analytical procedure was developed to monitor the ethanolysis of degummed soybean oil (DSO) using Fourier-transformed mid-infrared spectroscopy (FTIR) and methods of multivariate analysis such as principal component analysis (PCA) and partial least squares regression (PLS). The triglycerides (reagents) and ethyl esters (products) involved in ethanolysis were shown to have similar FTIR spectra. However, when the FTIR spectra derived from seven standard mixtures of triolein and ethyl oleate were treated by PCA at the region that represents the CO stretching vibration of ester groups (1700-1800 cm⁻¹), only two principal components (PC) were shown to capture 99.95% of the total spectral variance (92.37% for the former and 7.58% for the latter PC). This observation supported the development of a multivariate calibration model that was based on the PLS regression of the FTIR data. The prevision capability of this model was measured against 40 reaction aliquots whose ester content was previously determined by size exclusion chromatography. Only small discrepancies were observed when the two experimental data sets were treated by linear regression (R²=0.9837) and these deviations were attributed to the occurrence of non-modeled transient species in the reaction mixture (reaction intermediates), particularly at short reaction times. Therefore, the FTIR/PLS model was shown to be a fast and accurate method to predict reaction yields and to follow the in situ kinetics of soybean oil ethanolysis.     

New (1R,4R)-2-arylidene-p-menthan-3-ones with a bridging ester group in the arylidene fragment. Synthesis and behavior in liquid-crystalline systems

(1R,4R)-2-(4-Hydroxybenzylidene)- and (1R,4R)-2-(4"-hydroxybiphenyl-4-yl)methylene-p-menthan-3-ones were synthesized by condensation of (–)-menthone with O-tetrahydropyran-2-yl derivatives of 4-hydroxybenzaldehyde and 4"-hydroxy-4-formylbiphenyl, respectively, in a DMSO—base medium followed by the removal of the protective group. The reactions of these hydroxy derivatives with 4-alkylbenzoic, 4-alkyloxybenzoic, trans-4-alkylcyclohexane-4-carboxylic, and 4"-alkylbiphenyl-4-carboxylic acids afforded three series of new chiral esters. Compounds containing the arylidene moiety with three benzene rings were found to exhibit liquid-crystalline properties. The characteristic features of these compounds are discussed based on the results of studies by polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. It was found that the mesomorphic compounds under study can form a smectic A mesophase, twist grain boundary mesophases (TGBA), and blue phases in a wide temperature range. Upon dissolution of certain of chiral compounds in 4"-cyano-4-pentylbiphenyl, a rather high twisting power and the thermal stabilizing effect on mesophases were observed.     

Interaction of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-α]pyrimidine with methylene-active compounds and acid hydrolysis of its products

Reactions of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidine with sodium derivatives of pentane-2,4-dione, malonodinitrile, Meldrum acid, acetoacetic, cyanoacetic and malonic esters have been shown to give the respective substituted derivatives. Azinyl-ylidene tautomerism has been found to be characteristic of these compounds, the latter existing mainly in the ylidene form. The acid hydrolysis of pentane-2, 5-dione and cyanoacetic and malonic esters derivatives has been investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1961, November, 1993     

Regioselectivity in acylation of oligosaccharides catalyzed by the metalloprotease thermolysin

Investigation of the acylation scope of carbohydrates by metalloprotease thermolysin immobilized on Celite as biocatalyst has been carried out. The reactions were performed in DMSO, a good solvent for carbohydrates, where the enzyme has previously shown its activity in transesterifications of sucrose, maltose and maltose-containing oligosaccharides. Surprisingly, no reaction was observed for glucose or the glucose-containing disaccharides, trehalose and lactose. In contrast, laurate monoesters of several sucrose-containing tri- and tetrasaccharides were synthetized through a one step transesterification using vinyl laurate as the acylating agent. Enzyme regioselectivity was accurately determined by HPLC/MS and the structure of the main regioisomers was established by a combination of NMR experiments. The preferred position of acylation in all cases was the 2-OH of the α-d-glucopyranose moiety linked 1→2 to the β-d-fructofuranose unit. These results correlate with the regioselectivity observed in the case of the disaccharide sucrose. A general carbohydrate binding motif for catalysis by thermolysin is proposed.     

Cathodic synthesis of esters of 1,1,2,2-cycloalkanetetracarboxylic acids derived from 1,1,2,2-ethane- or ethylenecarboxylate esters

The cathodic electrolysis of esters of 1,1,2,2-ethane- or ethylenetetracarboxylic acids in the presence of dihaloalkanes leads to esters of 1,1,2,2-cycloalkanetetracarboxylic acids.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 217–220, January, 1992.     

First access to the spin-labelled β-amino acid POAC in an enantiopure state by resolution through its binaphthyl esters

Resolution of trans 3-(9-fluorenylmethyloxycarbonylamino)-1-oxyl-2,2,5,5-tetramethylpyrrolidine-4-carboxylic acid (Fmoc-POAC-OH) was quickly achieved upon esterification with (aR)-1,1′-binaphthyl-2,2′-diol, chromatographic separation of the obtained diastereomers, and facile saponification of the aryl ester function with removal of the chiral auxiliary.     

A new synthesis of highly functionalized 2H-pyran derivatives

Ethyl oxo-(2-oxo-cycloalkyl)-ethanoates undergo a smooth reaction with triphenylphosphine and dialkyl acetylenedicarboxylates via intramolecular Wittig reaction to produce spiro-cyclobutene derivatives. These spiro systems undergo electrocyclic ring opening reaction to produce electron-deficient 1,3-dienes, which spontaneously cyclize to 2H-pyran derivatives.     

N- and O-Alkylation of 3-indolylcyclopropylacetic acid derivatives

2,2-Dimethyl-3-(2-methyl-3-indolyl)cyclopropylacetic acid, its amide and esters, and the corresponding alcohol, viz., the product of ester reduction by LiAlH₄, were synthesized. The chemoselectivity of N- and O-alkylation of these compounds was studied. Selective monoalkylation at the nitrogen atom of the heterocycle, O-alkylation to the side chain, or dialkylation at both nucleophilic sites can be carried out under conditions of phase-transfer catalysis. The N-acylation at the indole fragment of nitrile of this acid occurs only under the Vilsmeier—Haak formylation conditions.