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Journal of Flow Chemistry
Authors: Klára Lövei, István Greiner, János Éles, Áron Szigetvári, Miklós Dékány, Sándor Lévai, Zoltán Novák, and György István Túrós

In medicinal chemistry, the development of synthetic procedures for the access of new heterocyclic systems as potential scaffolds is elementary. Herein, we report our results on the formation of small drug-like heterocycles, utilizing flow chemistry. This approach enables the extension of the reaction parameter window, including high-pressure/high-temperature or hazardous chemistry. In our work, various novel condensed tricyclic benzothiazoles fused with furo- and thieno-rings were synthesized applying a multistep continuous-flow protocol. The process includes two ring closure steps and a nitro group reduction step. Batch and telescoped continuous-flow syntheses were also designed and performed.

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the physical properties of the mesophases [ 5 ]. The presence of benzothiazole ring with electron-rich sulfur atom in the organic compound structure can influence on decrease of the ionization potential of the sample and generate smectic phase [ 6 , 7

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Abstract  

The carboxylato–Cu(II) complexes of type [Cu2(RCOO)4] and their benzothiazole adducts [Cu2(RCOO)4bt2] (bt = benzothiazole, R = CH3(CH2)n−2, n = 12, 14, 16, 18) form the main objectives of this study. The studied carboxylato–Cu(II) complexes are formed from dimeric units to polymeric chains (chromofor CuO5). The structural changes are due to coordination of ligand (benzothiazole). The polymeric chains of carboxylato–Cu(II) complexes degraded to discrete centrosymetric tetracarboxylate-bridged dimmers (chromofor CuO4N). These prepared compounds [Cu2(RCOO)4] and [Cu2(RCOO)4L2] were submitted to measurements relating to spectral (IR, UV–Vis) and thermal properties (TG, DTA, DSC).

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Quantitative structure-activity relationships (QSAR) between H 1 -histaminergic activity and chromatographic data have been investigated for derivatives of 2-[2-(phenylamino)thiazol-4-yl]ethanamine, 2-(2-benzyl-4-thiazolyl)ethanamine, 2-(2-benzhydrylthiazol-4-yl)ethanamine, 2-(1-piperazinyl)benzothiazole, and 2-(hexahydro-1 H -1,4-diazepin-1-yl)benzothiazole. TLC was performed on precoated silanized silica gel RP2 60F 254 plates impregnated with solutions of propionic acid, propionamide, and n -amylamine (used as amino acid analogs) and their mixtures, with two mobile phases — the systems were chosen as models of hH1R antagonistic interaction. Relationships between chromatographic and biological activity data were found by use of regression analysis. The correlations obtained for the thiazole and benzothiazole derivatives with H 1 -antihistamine activity (p A 2 (H 1 )) represent their interaction with all the proposed biochromatographic models (S1–S4). Some of the correlation equations obtained can be used to predict the pharmacological activity of new drug candidates. Lipophilicity data were obtained for the compounds and used in QSAR assays. The log P values of particular compounds are an extremely important indicator of this kind of activity.

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Quantitative structure-activity relationships (QSAR) between H 1 -histaminergic activity and chromatographic data have been investigated for derivatives of 2-[2-(phenylamino)thiazol-4-yl]ethanamine, 2-(2-benzyl-4-thiazolyl)ethanamine, 2-(2-benzhydrylthiazol-4-yl)ethanamine, 2-(1-piperazinyl)benzothiazole, and 2-(hexahydro-1 H -1,4-diazepin-1-yl)benzothiazole. TLC was performed on normal-phase plates (silica gel 60F 254 ) impregnated with solutions of amino acid analogs (propionic acid, propionamide, and n -amylamine) and their mixtures, and with two mobile phases — these systems were selected as models of antagonistic interaction with the human histamine H 1 -receptor. Lipophilicity data were obtained for the compounds examined and used in the QSAR assays. Relationships between chromatographic data and biological activity were found by regression analysis. The correlations obtained in these NP TLC experiments were more significant than those obtained in experiments with RP2 TLC, because of optimum fitting of the chromatographic conditions to the lipophilicity of the solutes. All the chromatographic models proposed should facilitate pre-selection of new drug candidates. Significant correlation ( R 2 = 0.92−0.96) was obtained between p A 2 (H 1 ) values predicted for the compounds by the use of the best equations and the p A 2 (H 1 ) values obtained for the compounds from biological tests.

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Summary  

In order to develop small molecular probes for imaging of Aβ plaques in the brain with Alzheimer’s disease, four benzothiazole derivatives as Aβ probes, 3’-125I-BTA, 3’-125I-CBTA, 3’-125I-BTA-Ac, and 3’-125I-CBTA-Ac were successfully prepared. The four probes displayed the following initial brain uptake: 10.28 %ID/g, 3.62 %ID/g, 3.33 %ID/g and 3.71 %ID/g at 2-minute post iv injection, respectively. The study of quantitative structure-activity relationship (QSAR) indicated that the initial brain uptake was correlated with molecule volume (V m) and dipole moment (D p), but the D p was the main factor. 3’-125I-BTA has the highest initial brain uptake among the four Aβ probes because of the smallest D p.

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Acta Biologica Hungarica
Authors: O. Temiz-Arpaci, T. Coban, B. Tekiner-Gulbas, B. Can-Eke, I. Yildiz, E. Aki-Sener, I. Yalcin, and M. Iscan

of some 2,5,6-substituted benzoxazole, benzimidazole, benzothiazole and oxazolo(4,5-b)pyridine derivatives. Arzneim. Forsch./Drug Res. 53 , 266-271. Synthesis and HIV-1 reverse transcriptase inhibitor activity of some 2

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The relative lipophilicity of bioactive derivatives of 2-[1-(4-alkylpiperazinyl)]benzothiazoles, 2-[4-(1-alkyl)piperidinyl]benzothiazoles, 2-( N,N ’-dimethyl-1,2-ethanediamino)benzothiazoles, and 2-1-(4-aminopiperidinyl)benzothiazoles has been determined by reversed-phase thin-layer chromatography. R M values of these compounds were determined with acetone-buffer mobile phases and extrapolated to 100% aqueous conditions. The lipophilicity was also determined by using optimized structures of the investigated compounds based on quantum mechanical calculations of the chemical structures (HyperChem 7.0). The distribution coefficients of the examined compounds were determined by use of the calculated ‘correction for dissociation’ descriptor. A correction was made based on the dissociation constants of the compounds, which were determined spectrophotometrically. We present a method for calculation of partition coefficients for ionizable compounds at a given pH. This property can be useful in analysis of quantitative structure-activity relationships. The distribution coefficients and the actual partition coefficient (at pH 7.4) were calculated for benzothiazole derivatives and for other drugs with different structures. The validity of calculations was checked by comparison with available experimental partition and distribution coefficients.

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Abstract  

The thermal behaviour of the mixed-ligand complexes of cobalt(II) and copper(I) ions with antipyrine derivatives of 1,2-ethanediamine or piperazine (BAMP and TAMEN), with water and with 2-mercapto-benzothiazole (Hmbt) was investigated. The complexes contain 2-mercaptobenzothiazole (Hmbt, in the case of cobalt(II) ion) or dimercaptobenzothiazine (mbt–mbt, in the case of copper(I) ion) molecules as ligands and perchlorate (ClO4 ) or thiocyanate (SCN – ) ion as counterion. By heating, water and ligands release the solid phase at lower temperature. At higher temperatures process of different organic reactions of ligands (e.g. polymerization, polycondensation) could be suggested to interpret the relative high final mass values.

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Journal of Thermal Analysis and Calorimetry
Authors: Manuel Temprado, Maria Roux, Archana Parameswar, Alexei Demchenko, James Chickos, and Joel Liebman

Abstract  

The present study reports a DSC study of the thio-and dithiocarbamates: 3H-benzoxazole-2-thione (2-mercaptobenzoxazole), 3H-benzothiazole-2-thione (2-mercaptobenzothiazole), thiazolidine-2-thione (2-mercapto-2-thiazoline), oxazolidine-2-thione (2-mercapto-2-oxazoline) and tetrahydro-1,3-oxazine-2-thione (5,6-dihydro-4H-1,3-oxazine-2-thiol) in the temperature interval T=268 K and the melting temperatures. Temperatures, enthalpies and entropies of fusion are reported. No solid-solid phase transitions were observed for the compounds in the temperature interval studied. The heat capacity of the compounds as a function of temperature was measured.

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