Fluorescent products of the reaction of mono-substituted guanidino compounds with benzoin-dimethylformamide

The fluorescent products formed from methylguanidine or phenylguanidine and benzoin in the presence of dimethylformamide are shown to be the corresponding 2-substituted amino-4, 5-diphenylimidazoles. They fluoresce most intensely at pH 9–10 and the fluorescence is stabilized by β-mercaptoethanol.     

On the reaction of superoxide ion with organochloric compounds

Superoxide ions were generated by the action of γ-radiation on water-alcohol solutions saturated with oxygen. The reaction of superoxide ions with sodium 2,4-dichlorophenoxyacetate and pentachlorophenol was studied. The reaction of O₂ ^?? with chloroaromatic compounds results in elimination of chloride ions and formation of phenyl radicals active in elimination of hydrogen atoms. The rate constant of the reaction between O₂ ^?? and 2,4-dichlorophenoxyacetate was calculated using the method of mathematical simulation.     

Chemiluminescence-HPLC for the assay of guanidino compounds

A chemiluminescence-HPLC system for the assay of serum guanidino compounds was established. In this study, we found that lucigenin added to the reaction mixture containing guanidino compounds and alkaline-ninhydrin reagent resulted in strong chemiluminescence. The lucigenin chemiluminescence was not derived from fluorescent derivatives of guanidino compounds or ninhydrin. The interaction of guanidino compounds and ninhydrin under alkaline conditions produced reactive oxygen species. We applied this phenomenon to the microanalysis of guanidino compounds.     

A novel general method for the synthesis of nitrones by reaction of nitroso compounds with anions of aliphatic nitro compounds

Anions of aliphatic nitro compounds R¹R²C=NO₂ ^– react with nitroso compounds RNO to give nitrones R¹R₂C=N(O)R. Salts of nitro compounds with metals and Et₃N, as well as trimethylsilyl nitronates in the presence of F^–, can serve as the sources of the anions. The structure of the nitrones was established by NMR spectroscopy. 1,3-Dipolar cycloaddition of a series of the nitrones obtained to olefins was investigated.For a brief communication see Ref. 1Translated from IzvestiyaAkademii Nauk. Seriya Khimicheskaya, No. 4, pp. 901–907, April, 1996.     

Fluorimetric determination of monosubstituted guanidino compounds with benzoin—dimethylformamide reagent

A sensitive fluorimetric method for the determination of monosubstituted guanidino compounds is based on their reaction in potassium hydroxide solution with benzoin in the presence of dimethylformamide. The fluorescence produced is stabilized by β-mercaptoethanol and shows excitation and emission maxima around 325 and 435 nm, respectively. The method is simple, selective for monosubstituted guanidino compounds, including polypeptides with one or two arginyl residues, and sensitive; compounds can be determined at concentrations as low as 0.08—0.22 nmol ml^-1.     

Electrode mechanism and voltammetric determination of selected guanidino compounds

The present review describes the recent results on the electrochemical activity of bio-guanidino compounds, such as famotidine, metformin, acyclovir, ganciclovir, zanamivir, moroxydine as well as guanidino compounds, such as S-[(2-guanidino-thiazol-4-yl)methyl]isothiourea hydrochloride, 2-guanidino-1,3-thiazole, 2-guanidinobenzimidazole. The focus is on analyzing the electrode mechanism of the guanidino compounds at the hanging mercury drop electrode and at the silver amalgam film electrode, as well as on the character of the square wave (SW) voltammetric signals. It has been stated, that the compounds can act as electrocatalysts — they are protonated and adsorbed at the surface of the electrode, after which the protonated forms of the compounds are irreversibly reduced, yielding their initial form and hydrogen. The experimental adsorption data obtained by measuring the differential capacity of the double layer, the zero charge potential, and the surface tension at the zero charge potential have established the adsorption processes underlying their electrochemical activity. The analytical application of the obtained voltammetric signals in the determination of these compounds in biological samples is also presented. This review concentrates on our own results in the context of general developments in the field.      

Interaction of anions with perfluoro aromatic compounds

The complexes formed by a variety of anions with perfluoro derivatives of benzene, naphthalene, pyridine, thiophene, and furan have been calculated using DFT (B3LYP/6-31++G**) and MP2 (MP2/6-31++G** and MP2/6-311++G**) ab initio methods. The minimum structures show the anion interacting with the pi-cloud of the aromatic compounds. The interaction energies obtained range between -8 and -19 kcal mol(-1). The results obtained at the MP2/6-31++G** and MP2/6-311++G** levels are similar. However, the B3LYP/6-31++G** results provide longer interaction distances and smaller interaction energies than do the MP2 results. The interaction energies have been partitioned using an electrostatic, polarization, and van der Waals scheme. The AIM analysis of the electron density shows a variety of topologies depending on the aromatic system considered.     

Interaction of multi-podal open-chained compounds with anions

Six kinds of naphthyl urea and thiourea podands were designed and synthesized. The interaction between these compounds and various guest anions are studied in molecular level via absorption, fluorescence and 1H NMR spectra. The experiments show that tri-podal urea or thiourea host can bind H2PO4-or HSO4-selectively and form a host-guest complex thus inducing a change in photophysical properties of host molecule. Through comparison between urea and thiourea compounds used as host molecules, the stability constants and stoichiometry of the complexes have been determined. The binding manner and possible structures of them have been proposed.     

Determination of guanidino compounds by anion-exchange chromatography and amperometric detection

Guanidino compounds were separated and determined by anion-exchange chromatography and electrochemical detection using a basic aqueous eluent and a nickel working electrode. It was found necessary to use a sample clean-up procedure prior to chromatographic analysis of uremic dialysate and serum samples. The effect of eluent hydroxide concentration on the retention of guanidino compounds was studied. Quantitative calibration showed that working curves were non-linear. Electrochemical detection for guanidino compounds with a nickel working electrode, while not selective, has high detection sensitivity. Detection limits for guanidino compounds ranged from 3 to 12 pmol.     

Generation of 1-aryl-3-methoxycarbonylnitrilimines and their reaction with halogen-containing unsaturated compounds

Thermal decomposition of 1-(4-methoxyphenyl)- and 1-(4-fluorophenyl)hepta(methoxycarbonyl)-3a,7a-dihydroindazoles at 135 °C in the presence of allyl or propargyl halides leads to the elimination of hexamethyl benzenehexacarboxylate and the formation of the corresponding pyrazolines or pyrazoles as the products of 1,3-dipolar cycloaddition of 1-aryl-3-methoxycarbonylnitrilimines to the multiple bonds of the substrates used. In the case of vinyl halides, the products of the target reactions are either obtained in low yields or nonexistent, with a side conversions taking place instead. Thus, for example, in the case of 1,1-dichloro-4-methylpenta-1,3-diene, besides hexamethyl benzenehexacarboxylate, 3,5,5-trichloro-2-methylpent-4-en-2-ol and arylchlorohydrazones MeO₂CC(Cl)=N-NHAr were unexpectedly isolated as the main products, as well.     

Formation of radical anions and not deprotonation starts the reaction of gamma-butyrolactone with potassium anions

A mechanism is proposed for the reaction of gamma-butyrolactone with the potassium anion as a two-electron-transfer reagent. Potassium hydride and potassium 4-potassiobutyrate are formed in this process as intermediates. These compounds deprotonate gamma-butyrolactone. Potassium lactone enolate, potassium butyrate, and hydrogen are the final reaction products.     

Kinetics of the reaction of superoxide anion-radical with olefins

Kinetic investigation of the reaction of electrochemically generated with perfluorooctene, styrene, and cyclohexene in acetonitrile, in the presence of tetraethylammonium perchlorate used as a background electrolyte, revealed that reacts with styrene and perfluorooctene at the double bond, and the reactivity of the olefins with respect to decreases with decrease in the electrophilicity of the substituents at the double bond: perfluorooctene > styrene > cyclohexene. The main transformation products of styrene are phthalic and benzoic acid esters.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 733–737, April, 1990.The authors thank V. B. Bol'evoi for his contribution to the discussion of the results obtained.     

Efficiency of superoxide anions in the inactivation of selected dehydrogenases

The most ubiquitous of the primary reactive oxygen species, formed in all aerobes, is the superoxide free radical. It is believed that the superoxide anion radical shows low reactivity and in oxidative stress it is regarded mainly as an initiator of more reactive species such as OH and ONOO^‐.In this paper, the effectiveness of inactivation of selected enzymes by radiation-generated superoxide radicals in comparison with the effectiveness of the other products of water radiolysis is examined. We investigate three enzymes: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH).We show that the direct contribution of the superoxide anion radical to GAPDH and ADH inactivation is significant. The effectiveness of the superoxide anion in the inactivation of GAPDH and ADG was only 2.4 and 2.8 times smaller, respectively, in comparison with hydroxyl radical. LDH was practically not inactivated by the superoxide anion.Despite the fact that the studied dehydrogenases belong to the same class of enzymes (oxidoreductases), all have a similar molecular weight and are tetramers, their susceptibility to free-radical damage varies. The differences in the radiosensitivity of the enzymes are not determined by the basic structural parameters analyzed. A significant role in inactivation susceptibility is played by the type of amino acid residues and their localization within enzyme molecules.     

The reaction of superoxide ion with vitamin K1 and its related compounds

The reaction of potassium superoxide with vitamin K₁ and its related compounds in the persence of crown ether gave the corresponding 2,3-oxide and phthalic acid. The oxidative cleavage of oxirane ring by superoxide ion has been observed with vitamin K₁ 2,3-oxide and certain epoxides.     

Observations on the reaction of nitronate anions with oxalyl chloride: a new method for the preparation of geminal chloronitroso compounds

A simple method for the preparation of geminal chloronitroso compounds from secondary nitro compounds via their derived nitronate anions is presented.     

Structure of radical anions of organosilicon compounds. INDO calculations of the radical anions of some organosilicon compounds

M. V. Lomonosov Moscow Institute of Fine Chemical Engineering. Translated from Zhurnal Strukturnoi Khimii, Vol. 29, No. 2, pp. 24–30, March–April, 1988.     

Generation of allylic indium by hydroindation of 1,3-dienes and one-pot reaction with carbonyl compounds

A hydroindation of 1,3-dienes by dichloroindium hydride (HInCl2) generates allylic indiums that react with carbonyl or imine moieties in a one-pot treatment. The former reaction proceeds in a radical manner, and the latter is ionic allylation. Moreover, both reactions require no additives such as radical initiators, Lewis acids, or transition metal catalysts.