Three Rings Schiff Base Ester Liquid Crystals: Experimental and Computational Approaches of Mesogenic Core Orientation Effect, Heterocycle Impact.

Three rings 2-hydroxypyridine liquid crystalline compounds have been prepared and fully characterized. The mesomorphic behavior of the prepared compounds has been investigated in terms of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Moreover, a comparative study between the prepared compounds and previously reported analogs has been discussed in terms of the orientation and position of the mesogenic core, in addition to the direction of the terminal alkyl chains. Furthermore, a detailed computational approach has been studied to illustrate the effect of geometrical and dimensional parameters on the type of the enhanced texture and the mesomorphic range and stability. The results of the DFT study revealed that the orientation of the mesogen could affect the mesomorphic behavior and this has been attributed in terms of the degree of the polarizability of the linking groups. This result has been confirmed by calculation of the net dipole moment and the molecular electrostatic potential that show how the mesogen orientation and position could impact the molecular charge separation. Finally, the effect of the pyridyl group has been also investigated in terms of the calculated aromaticity index and the π-π stacking.

Synthesis, modeling and biological evaluation of hybrids from pyrazolo[1,5c]pyrimidine as antileishmanial agents.

AIM: A new series of pyrazolo[1,5-c]pyrimidines were synthesized by different hybridization strategies. METHODOLOGY: All structures were confirmed by IR, 1H, 13C, 1H-13C heteronuclear multiple-quantum correlation (HMQC) spectra and microanalysis. They were evaluated for their in vitro antileishmanial activity against miltefosine and amphotericin B deoxycholate as reference drugs. RESULTS: The most active compounds 2a and 9a demonstrated superior potencies to miltefosine by ten- and six-fold, respectively, for the promastigote form, and by 5.5-fold for the amastigote form. Their binding scenario to Leishmania major pteridine reductase was rationalized by docking experiments. In addition, all compounds were safe for the experimental animals orally up to 150 mg/kg and parenterally up to 75 mg/kg. CONCLUSION: This study provides novel chemotype class for antileishmanial activity. [Formula: see text].

Synthesis and antibacterial activities of novel 2,5-diphenylindolo[2,3-e] pyrazolo[1',5':3",4"]pyrimido[2",1"-c] [1,2,4]triazines.

The formation of (E)-3-{2-(2,5-diphenylpyrazolo[1,5-c]pyrimidin-7-yl)hydrazono}indolin-2-ones 3 has been achieved by condensation of equimolar amounts of 7-hydrazino-2,5-diphenylpyrazolo[1,5-c]pyrimidine (1) and isatin (or isatin derivatives) 2 at room temperature. The (E)-products could be isomerized into corresponding the (Z)-3 isomers. Reactions of the latter fused heterocyclic hydrazones towards different electro-philic reagents yielded the corresponding 3-substituted derivatives 4-7. Dehydrative cyclisation of the hydrazones 3 using phosphorus oxychloride afforded the 2,5-diphenyl- indolo[2,3-e]pyrazolo[1',5':3",4"]pyrimido[2",1"-c][1,2,4] triazines 13. The polyfused heterocyclic ring system 13 underwent electrophilic substitution reactions at position 4 rather than at position 3. The 3-bromo isomer of 17 was prepared by a sequence of reactions starting from 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H)-thione (11). The orientation of the electrophilic attack was supported by spectroscopic and chemical evidence. Some of the synthesized compounds were found to possess slight to moderate activity against the microorganisms Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa.

Synthesis and antibacterial activities of novel imidazo[2,1-b]-1,3,4-thiadiazoles.

2-Amino-5-(2-aryl-2H-1,2,3-triazol-4-yl)-1,3,4-thiadiazoles 2-4 have been synthesized by the reaction of 2-aryl-2H-1,2,3-triazole-4-carboxylic acids 1 with thiosemicarbazide. Their reaction with phenacyl (p-substituted phenacyl) bromides led to formation of the respective 6-aryl-2-(2-aryl-2H-1,2,3-triazol-4-yl)imidazo[2,1-b]-1,3,4-thiadiazoles 5. Reactivity of the latter fused ring towards reaction with different electrophilic reagents afforded the corresponding 5-substituted derivatives 6-8. The structure of the above compounds was confirmed from their spectral characteristics. Some of these compounds were found to possess slight to moderate activity against the microorganisms Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa, and Escherichia coli.