Synthesis, molecular structure and spectroscopic studies of some new quinazolin-4(3H)-one derivatives; an account on the N- versus S-Alkylation

Synthesis of Novel Benzenesulfonamide-Bearing Functionalized Imidazole Derivatives as Novel Candidates Targeting Multidrug-Resistant Mycobacterium abscessus Complex

Infections caused by drug-resistant (DR) Mycobacterium abscessus (M. abscessus) complex (MAC) are an important public health concern, particularly when affecting individuals with various immunodeficiencies or chronic pulmonary diseases. Rapidly growing antimicrobial resistance among MAC urges us to develop novel antimicrobial candidates for future optimization. Therefore, we have designed and synthesized benzenesulfonamide-bearing functionalized imidazole or S-alkylated derivatives and evaluated their antimicrobial activity using multidrug-resistant M. abscessus strains and compared their antimycobacterial activity using M. bovis BCG and M. tuberculosis H37Ra. Benzenesulfonamide-bearing imidazole-2-thiol compound 13, containing 4-CF₃ substituent in benzene ring, showed strong antimicrobial activity against the tested mycobacterial strains and was more active than some antibiotics used as a reference. Furthermore, an imidazole-bearing 4-F substituent and S-methyl group demonstrated good antimicrobial activity against M. abscessus complex strains, as well as M. bovis BCG and M. tuberculosis H37Ra. In summary, these results demonstrated that novel benzenesulfonamide derivatives, bearing substituted imidazoles, could be further explored as potential candidates for the further hit-to-lead optimization of novel antimycobacterial compounds.

Antioxidant and Cytotoxic Activity of New Polyphenolic Derivatives of Quinazolin-4(3H)-one: Synthesis and In Vitro Activities Evaluation

The development of hybrid molecules with significant human therapeutic properties is one of the main approaches of pharmaceutical research. One of the most important pharmacophores is the quinazolin-4(3H)-one heterocycle moiety, due to its wide range of biological activities. By its derivatization with polyphenolic compounds, in our previous research, it proved to possess a good antiradical activity of ortho-diphenolic derivatives of quinazolin-4(3H)-one. In this study, we developed two new series of compounds, with an additional phenolic group or with a methyl group on the thioacetohydrazone fragment. The methods used to evaluate the activity of the compounds were radical scavenging, reduction of oxidizing reagents and transition metals' ions chelation assays. Quantum descriptors were also calculated in order to evaluate the influence of substituents and their position on the activity of the compounds. The cytotoxic activity was evaluated using normal human foreskin fibroblast cells (BJ) and two cancerous cell lines, lung adenocarcinoma cells (A549) and prostate carcinoma cells (LNCaP). The results obtained for the pyrogallol derivatives showed a high antioxidant activity compared to ascorbic acid and Trolox. All the synthesized compounds displayed a higher cytotoxicity against the cancerous cell types and a high cytocompatibility with the normal cells. The antioxidant activity was deeply influenced by the addition of the third phenolic group in the synthesized molecules.

Synthesis of New Phenolic Derivatives of Quinazolin-4(3H)-One as Potential Antioxidant Agents-In Vitro Evaluation and Quantum Studies

Considering the important damage caused by the reactive oxygen (ROS) and nitrogen (RNS) species in the human organism, the need for new therapeutic agents, with superior efficacy to the known natural and synthetic antioxidants, is crucial. Quinazolin-4-ones are known for their wide range of biological activities, and phenolic compounds display an important antioxidant effect. Linking the two active pharmacophores may lead to an increase of the antioxidant activity. Therefore, we synthesized four series of new hybrid molecules bearing the quinazolin-4-one and phenol scaffolds. Their antioxidant potential was evaluated in vitro, considering different possible mechanisms of action: hydrogen atom transfer, ability to donate electrons and metal ions chelation. Theoretical quantum and thermodynamical calculations were also performed. Some compounds, especially the ortho diphenolic ones, exerted a stronger antioxidant effect than ascorbic acid and Trolox.

Synthesis, DFT Molecular Geometry and Anticancer Activity of Symmetrical 2,2'-(2-Oxo-1H-benzo[d]imidazole-1,3(2H)-diyl) Diacetate and Its Arylideneacetohydrazide Derivatives

To identify new candidate anticancer compounds, we here report the synthesis of benzimidazole derivatives: diethyl 2,2′-(2-oxo-1H-benzo[d]imidazole-1,3(2H)-diyl) diacetate and its arylideneacetohydrazide derivatives, using ultrasonic irradiation and conventional heating. The compounds were confirmed by Nuclear magnetic resonance (NMR) (JEOL, Tokyo, Japan) and Fourier transform infrared spectroscopy (FTIR) spectroscopy (Thermoscientific, Waltham, MA, USA). The molecular structure and electronic properties of the studied compounds were predicted for the acetohydrazide hydrazones. These compounds exist as a mixture of configurational and conformational isomerism as well as amido-amidic acid tautomerism. The NMR spectral data proved the predominance of syn-E amido isomers. In addition, density functional theory (DFT) predicted stability in the gas phase and showed that syn-E amido isomers are the most stable in the presence of an electron donating group, while the anti-isomer is the most stable in the presence of electron-attracting substituents. The anticancer activity of these synthetic compounds 6a, 6b and 6c towards both colon cancer (HCT-116) and cervical cancer (HeLa) cells was examined by MTT assay and DAPI staining. The MTT assay revealed a strong antiproliferative effect against the cancer cells at low concentrations, and interestingly, no significant inhibitory action against the non-cancerous cell line, HEK-293. The IC50 values for HCT-116 were 29.5 + 4.53 µM, 57.9 + 7.01 µM and 40.6 + 5.42 µM for 6a, 6b, and 6c, respectively. The IC50 values for HeLa cells were 57.1 + 6.7 µM, 65.6 + 6.63 µM and 33.8 + 3.54 µM for 6a, 6b, and 6c, respectively. DAPI staining revealed that these synthesized benzimidazole derivatives caused apoptotic cell death in both the colon and cervical cancer cells. Thus, these synthetic compounds demonstrate encouraging anticancer activity as well as being safe for normal human cells, making them attractive candidates as anticancer agents.

Synthesis of Quinolino[1,2-c]quinazolin-6-one Derivatives via Formal (4+2)-Cycloaddition of Alkenes to Quinazolinе-Derived N-Acyliminium Cations: An Experimental and Theoretical Study

3-Aryl-4-hydroxy-1-methyl-3,4-dihydroquinazolin-2(1H)-ones were synthesized by reduction of 3-aryl-1-methylquinazoline-2,4(1H,3H)-diones with sodium triethylborohydride and studied as precursors of N-acyliminium cations that were expected to be trapped with various alkenes as (4+2)-cycloadducts. Unsubstituted 3-aryl-4-hydroxy-1-methyl-3,4-dihydroquinazolin-2(1H)-ones in the presence of BF3·Et2O failed to produce the desired cycloadducts probably due to a homooligomerization reaction involving N-acyliminium intermediates. To prevent this side reaction, we found it necessary to introduce substituents at both positions C6 and C8 of the quinazoline ring and C4′ of the 3-phenyl substituent. Utilizing bromine atoms as substituents at C6 and C8, N-acyliminium cations generated from 3-aryl-6,8-dibromo-4-hydroxy-1-methyl-3,4-dihydroquinazolin-2(1H)-ones in the presence of BF3·Et2O smoothly reacted with such alkenes as indene, acenaphthylene, styrene, α-methylstyrene to give new quinolino[1,2-c]quinazolin-6-one derivatives with high regio- and stereoselectivity. Density functional theory calculations were performed at the M06-2x/cc-pVDZ level to obtain an insight into the mechanism of the (4+2)-cycloaddition reaction of quinazoline-derived N-acyliminium cations to alkenes.

Design, synthesis, and pharmacological characterization of some 2-substituted-3-phenyl-quinazolin-4(3H)-one derivatives as phosphodiesterase inhibitors

Some 3-phenyl-quinazolin-4(3H)-one-2-thioethers (3a-e, 5a,b, 7a-e, 9a-d, 10a-d, and 12) along with 2-aminoquinazoline derivatives 13a-c were prepared and screened for their in vitro phosphodiesterase (PDE) inhibitory activity. Some compounds such as 7d,e, 9a,b,d, 10a,d, and 13b exhibited promising activity as compared with the non-selective PDE inhibitor IBMX. This inhibitory activity was validated by molecular docking in the active site of PDE7A and PDE4 to investigate their selectivity. Furthermore, the most active compound 10d (IC₅₀  = 1.15 μM) was tested in vivo using behavioral tests. Compound 10d was able to pass the blood-brain barrier and improve scopolamine-induced cognitive deficits. Therefore, this core can be considered as a promising scaffold for further optimization to obtain new compounds with better PDE7A selective inhibition.

New Nitro-Laterally Substituted Azomethine Derivatives; Synthesis, Mesomorphic and Computational Characterizations

Two new homologues series, based on two rings of the azomethine central group bearing the terminal alkoxy group of various chain lengths, were prepared. The alkoxy chain length varied between 6 and 16 carbons. The other terminal wing in the first series was the F atom, and the compound is named N-4-florobenzylidene-4-(alkoxy)benzenamine (In). The second group of compounds included a lateral NO2 substituent in addition to the terminal F atom, named N-(4-fluoro-3-nitrobenzylidene)-4-(alkyloxy)aniline (IIn). Mesomorphic and optical properties were carried out via differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Elemental analyses, FT-IR, and NMR spectroscopy were carried out to elucidate the molecular structures of the synthesized groups. Mesomorphic investigations indicated that all the synthesized homologues (In) were monomorphic, possessing the smectic A (SmA) phase monotropically, while the second group (IIn) members were non-mesomorphic. The experimental data indicated that the formation of the mesophase is affected by the protrusion of the lateral nitro group. The disruption of the mesophase in the second group was attributed to the increase of its molecular width, which affects its lateral intermolecular interactions. The computational simulations were in agreement with the experimental data. On the other hand, the location of NO2 group within the molecular geometry increased the melting temperature of the molecule, and thus, affected their thermal and physical properties. By discussing the estimated parameters, it was found that the molecular architecture, the dipole moment, and the polarizability of the investigated compounds are highly affected by the electronic nature and position of the terminal and lateral substituents as well as their volumes.

Optical and Geometrical Characterizations of Non-Linear Supramolecular Liquid Crystal Complexes

Nonlinear architecture liquid crystalline materials of supramolecular 1:1 H-bonded complexes (I/II and I/III) were prepared through a self-assembly intermolecular interaction between azopyridine (I) and 4-n-alkoxybenzoic acid (II) as well as 4-n-alkoxyphenylazo benzoic acid (III). The H-bond formation of the prepared supramolecular hydrogen bonded (SMHB) complexes was confirmed by Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Optical and mesomorphic behaviors of the prepared complexes were studied by polarized optical microscopy (POM) as well as DSC. Theoretical calculations were performed by the density functional theory (DFT) and used to predict the molecular geometries of the synthesized complexes, and the results were used to explain the experimental mesomorphic and optical properties in terms of their estimated thermal parameters. Ordinary and extraordinary refractive indices as well as birefringence at different temperatures were investigated for each sample using an Abbe refractometer and modified spectrophotometer techniques. Microscopic and macroscopic order parameters were calculated for individual compounds and their supramolecular complexes.

Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation

New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands attributed to the presence of intermolecular H-bond interactions were confirmed by FT-IR spectroscopy. All prepared complexes possessed an enantiotropic nematic phase with a broad temperature nematogenic range. Phases were confirmed by miscibility with a standard nematic (N) compound. A comparison was constructed to investigate the influence of the incorporation of the azophenyl moiety on the mesomeric behavior of corresponding five-membered complexes. It was found that the present complexes observed induced a wide nematic phase with relatively higher temperature ranges than the five aromatic systems. Density functional theory (DFT ) suggested the nonlinear geometry of the formed complex. The results of the DFT explained the nematic mesophase formation. Moreover, the π-π stacking of the aromatic moiety in the phenylazo acid plays an effective role in the mesomorphic thermal stability. The energy difference between the frontier molecular orbitals, HOMO (highest occupied) and LUMO (lowest occupied), and the molecular electrostatic potential (MEP) of the prepared complexes were estimated by DFT calculations. The results were used to illustrate the observed nematic phase for all H-bonded supramolecular complexes. Finally, photophysical studies were discussed which were carried out by UV spectroscopy connected to a hot stage.

Experimental and Theoretical Approaches of New Nematogenic Chair Architectures of Supramolecular H-Bonded Liquid Crystals

New four isomeric chair architectures of 1:1 H-bonded supramolecular complexes were prepared through intermolecular interactions between 4-(2-(pyridin-4-yl)diazenyl-(2-(or 3-)chlorophenyl) 4-alkoxybenzoates and 4-n-alkoxybenzoic acids. The H-bond formation of all complexes was confirmed by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Mesomorphic characterization was carried by DSC and polarized optical microscopy (POM). It was found that all prepared laterally chloro-substituted supramolecular complexes were nematogenic, and exhibited nematic phase and low melting temperature. The thermal stability of the nematic mesophase observed depends upon the location and spatial orientation of the lateral Cl- atom in as well as the length of terminal chains. Theoretical calculations were carried out within the paradigm of the density functional theory (DFT) in order to establish the molecular conformation for the formed complexes and estimate their thermal parameters. The results of the computational calculations revealed that the H-bonded complexes were in a chair form molecular geometry. Additionally, out of the acquired data, it was possible to designate the influence of the position and orientation of the lateral group as well as the alkoxy chain length on the stability of the nematic phase.

New wide-stability four-ring azo/ester/Schiff base liquid crystals: synthesis, mesomorphic, photophysical, and DFT approaches

DSC thermograms of some prepared compounds: (a) recorded from second heating and (b) from cooling at a rate of ±10 °C min⁻¹.

Synthesis, Optical, and Geometrical Approaches of New Natural Fatty Acids' Esters/Schiff Base Liquid Crystals

Schiff base liquid crystals, known as [4-(hexyloxy)phenylimino)methyl]phenyl palmitate (IA), [4-(hexyloxy)phenylimino)methyl]phenyl oleate (IIA) and [4-(hexyloxy)phenylimino)methyl]phenyl linoleate (IIIA), were synthesized from palmitic, oleic, and linoleic natural fatty acids. The prepared compounds have been investigated for their thermal and optical behavior as well as phase formation using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Molecular structures of all studied compounds were confirmed via elemental analysis, FT-IR, 1H NMR, and 13C NMR. Smectic phase is the observed mesophase for all compounds; however, their type and range depend upon the terminal alkanoate chains attached to the phenyl ring. Computational calculations, Density functional theory (DFT), energy difference of the frontier molecular orbital (FMOs), as well as the thermodynamic parameters of different molecular configurations isomers were discussed. It was found that the mesophase behavior and the geometrical characteristics were affected by the degree of unsaturation of fatty terminal chains. Furthermore, the geometrical structure of the CH=N linkage plays an important role in the thermal stability and optical transition temperature.

Phase Behavior and DFT Calculations of Laterally Methyl Supramolecular Hydrogen-Bonding Complexes

Four new series of laterally methyl-substituted hydrogen-bonded supramolecular complexes were prepared. The prepared complexes were thermally investigated by differential scanning calorimetry (DSC) and phases identified by polarized light microscopy (PLM). Supramolecular hydrogen-bonded complexes formed from a 1:1 mixture of any two derivatives, bearing different alkoxy chains, of 4-alkoxyphenylazobenzoic acid and 4-(2-(pyridin-4-yl)diazenyl-(2-(or 3-)methylphenyl) 4-alkoxybenzoate. The investigated 1:1 mixture made by introducing a lateral methyl group by different spatial orientation angles into pyridine-based components. All new complexes were confirmed by Fourier-transform infrared spectroscopy (FTIR) and computational calculations used to study their stabilities. It is found that the prepared complexes are dimorphic, exhibiting smectic C and enhanced nematic phases. A comparison was made between the new series and previously investigated simpler complexes, revealed that the incorporation of the phenylazo group elongate the mesogenic part and hence broad nematic phases were obtained with high stability.

DFT Calculations and Mesophase Study of Coumarin Esters and Its Azoesters

Two groups of coumarin derivatives, 4-methyl-2-oxo-2H-chromen-7-yl 4-alkoxybenzoates (coumarin esters), In, and 4-methyl-2-oxo-2H-chromen-7-yl 4-(2-(4-alkoxyphenyl)diazenyl) benzoates (coumarin azoesters), IIn, were synthesized and investigated for their mesophase behavior and stability. Each group constitutes five series that differ from each other by length of the mesogenic part. Within each homologous series, the length of the terminal alkoxy group varies between 6, 8, 10, 12 and 16 carbons. Mesophase behavior was investigated by differential scanning calorimetry (DSC) and identified by polarized light microscopy (PLM). Density functional theory (DFT) calculations for coumarin derivatives were discussed. The results revealed that the incorporation of azo group incorporated in the mesogenic core decreases the energy differences, increases the dipole moments and stabilities of coumarin azoesters series more than coumarin esters.