Vol. 18 No. 3(71) (2020)
Published:
2020-09-18
Original Researches
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α(β)-Sulfonyl(phosphoryl)acrylonitriles and enamines in the synthesis of biologically active heterocycles
Functionalization of heterocyclic systems with sulfur- and phosphorus-containing pharmacophores has long shown itself as an effective method for construction of new bioactive substances. At the same time, some types of the compounds are represented by only a few examples, and it prevents further evaluation of the contribution of certain structural elements to biological effects of the sulfonyl- and phosphoryl-substituted heterocyclic derivatives studied. Therefore, a relevant task for organic and medicinal chemistry still remains development of new methods for the synthesis of heterocyclic compounds with sulfonyl and phosphoryl groups, as well as determination of the biological activity of these substances. A structural variety of sulfonyl- and phosphoryl-substituted heterocycles can be achieved by using heterofunctional low-molecular compounds with sulfonyl and phosphoryl groups. This review highlights the information on biologically active heterocyclic compounds synthesized from acrylonitriles and enamines of sulfones, phosphine oxides, and phosphonates series.
Received: 05.02.2020
Revised: 25.05.2020
Accepted: 27.08.2020
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Kinetic parameters of ionizing power of solvents. The nature of solvation effects in heterolysis of 2-aryl-2-chloroadamantanes
Aim. To find out the possibility of using tertiary substrates as benchmarks for determining the kinetic parameters of the ionizing ability of solvents Y.
Results and discussion. The rate of heterolysis of tertiary substrates, especially adamantyl derivatives, is highly dependent on the effect of nucleophilic solvation. This effect increases with increasing spatial complications. The use of 2-aryl-2-halogenadamantanes as reference points is impractical because the conjugation of the positive charge with the phenyl strongly depends on the nature of the solvent. The least sensitive to the effects of specific solvation is tBuCl. Unlike tertiary compounds, the heterolysis rate of secondary ones does not depend on the nucleophilicity of the solvent.
Experimental part. The kinetic data of tertiary substrates obtained by different methods (conductometric, chromatographic, verdazyl) were generalized using correlation analysis.
Conclusions. Tertiary substrates are unsuitable as benchmarks for determining the ionizing ability of solvents due to the negative effect of nucleophilic solvation. Secondary substrates are less sensitive to the effects of specific solvation. The rate of heterolysis of secondary substrates is described by the parameters of polarity f(ɛ) and electrophilicity E or solvatochromic parameters of the ionizing capacity of the solvent Z(ЕТ).
Received: 25.06.2020
Revised: 15.07.2020
Accepted: 27.08.2020
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P-Stereogenic diamondoid phosphines
Despite diamondoid phosphines have found many synthetic applications and are even available commercially the chemistry of chiral diamondoid phosphines remains largely unexplored.
Aim. To develop the convenient preparative method for the preparation of sterically-congested P-stereogenic secondary diamodoidyl phosphines as potential organocatalysts and ligands in the asymmetric synthesis.
Results and discussion. A convenient method for the synthesis of P-stereogenic diamondoid phosphines with high yields through the phosphorylation of hydroxydiamondoids in trifluoroacetic acid followed by the reduction of the corresponding asymmetric chlorophosphonates has been proposed. The secondary phosphines obtained form stable complexes with borane that can be used to separate diamondoid phosphines into enantiomers.
Experimental part. The experimental procedures for the preparation of 1- and 4-diamantyl-1-adamantyl- and phenylphosphines were developed; the structures of new compounds were confirmed by NMR and HRMS spectral data.
Conclusions. A number of P-stereogenic mixed diamondoidylaryl phosphines and the secondary phosphines containing exclusively diamondoid substituents has been prepared. A degree of steric bulkiness is determined by the combination of diamondoid substituents around a phosphorus atom where 1-diamantyl derivatives are the most sterically-congested. The compounds obtained are potential ligands in asymmetric catalysis.
Received: 31.03.2020
Revised: 24.06.2020
Accepted: 27.08.2020
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p-Nitrophenyl ester of (diphenylphosphoryl)acetic acid as a reagent for the synthesis of 2-(phosphorylmethyl)benzimidazole
Aim. To expand the synthetic potential of the activated esters of diphenylphosphorylacetic acid for the synthesis of phosphorylated benzimidazoles.
Results and discussion. A new synthetic pathway to obtain 2-((diphenylphosphoryl)methyl]-1H-benzimidazole has been found via the reaction of p-nitrophenyl ester of (diphenylphosphoryl)acetic acid and o-phenylenediamine. The complexing ability of 2-[(diphenylphosphoryl)methyl]-1H-benzimidazole for metal ions of the twelvth group has been determined. The chelate complex with CdCl2 has been prepared and studied by the X-ray diffraction method.
Experimental part. The two-step reaction of p-nitrophenyl ester of (diphenylphosphoryl)acetic acid with o-phenylenediamine resulted in 2-[(diphenylphosphoryl)methyl]-1H-benzimidazole with a high yield. Its complex with CdCl2 was synthesized. Molecular structures of all compounds prepared were confirmed by the methods of 1H and 13C NMR spectroscopy, LC/MS spectrometry, elemental analysis; for the CdCl2 complex – by the data of X-ray diffraction analysis.
Conclusions. A new synthetic approach to obtain 2-(phosphorylmethyl)benzimidazole via the reaction of the activated ester of phosphorylacetic acid and o-phenylenediamine has been carried out. It has been shown that 2-[(diphenylphosphoryl)methyl]-1H-benzimidazole is capable of forming chelating complexes with the salts of cadmium in the neutral medium.
Received: 25.06.2020
Revised: 18.07.2020
Accepted: 27.08.2020
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Phosphorylated calix[4,8]arenes improve the RP HPLC separation of benzene derivatives
Aim. To study the effect of 5,11,17,23-tetrakis(diisopropoxyphosphonyl)-25,26,27,28-tetrapropoxycalix[4]arene and oсtаkis(diethoxyphosphoryloxy)-tert-butylcalix[8]аrene additives to the MeCN – H2O mobile phase (86:14) on the selectivity of the separation of aromatic compounds by the reversed-phase high performance liquid chromatography (RP HPLC) using a Separon SGX C18 support.
Results and discussion. The process of complexation of phosphorylated calix[4,8]arenes with benzene derivatives in the mobile phase plays a key role in the RP HPLC separation of analytes. The stability constants of the inclusion complexes and the chromatographic separation coefficients of the analytes depend on the nature of the aromatic compounds and the cavity size of the calixarene macrocycle.
Experimental part. The HPLC analysis was performed in acetonitrile – water (86:14) solution using a Separon SGX C18 column. The stability constants of the calixarene complexes were determined using the dependence of 1/k’ chromatographic parameters of benzene derivatives on the calixarene concentration in the mobile phase. Molecular modelling of the calixarene complexes was carried out using a Hyper Chem 8.0 program.
Conclusions. The phosphorus-contained calixarenes due to their ability to form supramolecular complexes with aromatic molecules can be used as additives to the RP HPLC mobile phase and improve separation of benzene derivatives.
Received: 14.05.2020
Revised: 24.06.2020
Accepted: 27.08.2020
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The HPLC-MS determination of pharmacokinetic parameters of morpholinium 2-((4-(2-methoxyphenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)thio)acetate
Aim. To study pharmacokinetic parameters of the potential active pharmaceutical ingredient (API) morpholinium 2-((4-(2-methoxyphenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)thio)acetate in the blood plasma of rats when administered intraperitoneally.
Results and discussion. The HPLC-MS method of determination of morpholinium 2-((4-(2-methoxy)-5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)thio)acetate in the blood plasma of non-linear rats has been adopted to study of pharmacokinetic parameters of the compound. It has been proven that high levels of API extraction from the blood plasma when using methanol for protein precipitation were observed. The measurement of the concentration of the drug substance studied in the blood plasma at different time intervals after injection allowed us to plot the pharmacokinetic curve and calculate the pharmacokinetic parameters.
Experimental part. The Agilent 1260 Infinity liquid chromatography system consisted of a degasser, binary pump, autosampler, column thermostat, diode-matrix detector, single-quadrupole mass spectrometric detector (Agilent 6120). The pharmacokinetic study was performed in sexually mature white nonlinear rats of two sexes. The active pharmaceutical ingredient morpholinium 2-((4-(2-methoxy)-5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)thio)acetate, was administered in the isotonic solution intraperitoneally in the dose of 50 mg/kg.
Conclusions. The pharmacokinetic curve has been plotted, and the pharmacokinetic parameters of morpholinium 2-((4-(2-methoxy)-5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)thio)acetate in the blood plasma when administered intraperitoneally have been calculated.
Received: 30.06.2020
Revised: 08.08.2020
Accepted: 27.08.2020
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The preparative synthetic approach to α,α-difluoro-γ-aminobutyric acid
Aim. To develop a convenient synthetic approach for the preparation of multigram amounts of 2,2-difluoro-γ-aminobutyric acid, which is pharmacologically promising analog of γ-aminobutyric acid (GABA).
Results and discussion. α,α-Difluoro-γ-aminobutyric acid (2,2-difluoro-GABA, 53 g) has been synthesized using the reaction of ethyl bromodifluoroacetate (EBDFA) addition to benzyl acrylate in the presence of copper as a key stage.
Experimental part. The reaction of EBDFA with benzyl acrylate in the presence of copper and tetramethylethylenediamine (TMEDA) was carried out; the resulting product was transformed to the target α,α-difluoro-γ-aminobutyric acid (in the form of hydrochloride) by consecutive debenzylation, Curtius rearrangement and treatment with hydrochloric acid to remove protecting groups. The synthesis was scaled up for the preparation of 53 g of α,α-difluoro-γ-aminobutyric acid. The ethyl ester of α,α-difluoro-γ-aminobutyric acid was also prepared and further transformed to 3,3-difluoropyrrolidine-2-one. The structure of the compounds synthesized was confirmed by 1Н, 13C and 19F NMR spectroscopy, mass spectrometry and elemental analysis.
Conclusions. It has been shown that the synthetic approach developed can be used for the preparation of α,α-difluoro-γ-aminobutyric acid in multigram amounts. The pathway is much more convenient, cheaper and safer compared to the method earlier described.
Received: 30.07.2020
Revised: 19.08.2020
Accepted: 27.08.2020
