First Exclusive Stereo- and Regioselective Preparation of 5-Arylimino-1,3,4-Selenadiazole Derivatives: Synthesis, NMR analysis, and Computational Studies

Isoselenocyanates are valuable coupling partners required for preparing key chemical intermediates and biologically active molecules in an accelerated and effective way. Likewise, (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides have been employed in numerous one-step heteroannulation reactions to assemble the structural core of several various kinds of heterocyclic compounds. Here, we describe the inverse electron demand 1,3-dipolar cycloaddition reaction of isoselenocyanates with a variety of substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides to generate, regioselectively and stereoselectively, a series of 5-arylimino-1,3,4-selenadiazole derivatives comprising a multitude of functional groups on both aryl rings. The synthetic method features gentle room-temperature conditions, wide substrate scope, and good to high reaction yields. The selenadiazoles were separated by gravity filtration in all instances and chemical structures were validated by multinuclear NMR spectroscopy and high accuracy mass spectral measurements. First conclusive molecular structure elucidation of the observed 5-arylimino-selenadiazole regioisomer was verified by single-crystal X-ray diffraction analysis. Crystal-structure measurement was successfully carried out on (Z)-1-(4-(4-iodophenyl)-5-(p-tolylimino)-4,5-dihydro-1,3,4-selenadiazol-2-yl)ethan-1-one and (Z)-1-(5-((4-methoxyphenyl)imino)-4-(4-(methylthio)phenyl)-4,5-dihydro-1,3,4-selenadiazol-2-yl)ethan-1-one. Likewise, the (Z)-geometry of the hydrazonoyl chloride reactant was proven by X-ray diffraction studies. As representative examples, crystal-structure determination was carried out on (Z)-2-oxo-N-phenylpropanehydrazonoyl chloride and (Z)-N-(3,5-bis(trifluoromethyl)phenyl)-2-oxopropanehydrazonoyl chloride. Density functional theory calculations at the B3LYP-D4/def2-TZVP level were conducted to support the noted experimental findings and suggested mechanism.

Synthesis of 4-Aryl-1,3,4-benzotriazepinones from Isatoic Anhydrides and Hydrazonyl Chlorides

An efficient synthesis of 4-aryl-1,3,4-benzotriazepinones from readily available isatoic anhydrides and hydrazonyl chlorides was developed. In this facile protocol, a series of functionalized 1,3,4-benzotriazepinones were conveniently obtained with broad substrate scope and excellent functional group tolerance.

First X-ray Crystal Structure Characterization, Computational Studies, and Improved Synthetic Route to the Bioactive 5-Arylimino-1,3,4-thiadiazole Derivatives

N-arylcyanothioformamides are useful coupling components for building key chemical intermediates and biologically active molecules in an expedited and efficient manner. Similarly, substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides have been utilized in numerous one-step heteroannulation reactions to assemble the structural core of several different types of heterocyclic compounds. Herein, we demonstrate the effectiveness of the reaction of N-arylcyanothioformamides with various substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides to produce, stereoselectively and regioselectively, a range of 5-arylimino-1,3,4-thiadiazole derivatives decorated with a multitude of functional groups on both aromatic rings. The synthetic methodology features mild room-temperature conditions, large substrate scope, wide array of functional groups on both reactants, and good to high reaction yields. The products were isolated by gravity filtration in all cases and structures were confirmed by multinuclear NMR spectroscopy and high accuracy mass spectral analysis. Proof of molecular structure of the isolated 5-arylimino-1,3,4-thiadiazole regioisomer was obtained for the first time by single-crystal X-ray diffraction analysis. Crystal-structure determination was carried out on (Z)-1-(5-((3-fluorophenyl)imino)-4-(4-iodophenyl)-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one and (Z)-1-(4-phenyl-5-(p-tolylimino)-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one. Similarly, the tautomeric structures of the N-arylcyanothioformamides and (Z)-geometries of the 2-oxo-N-phenylpropanehydrazonoyl chloride coupling partners were proven by X-ray diffraction studies. As representative examples, crystal-structure determination was carried out on (4-ethoxyphenyl)carbamothioyl cyanide and (Z)-N-(2,3-difluorophenyl)-2-oxopropanehydrazonoyl chloride. Density functional theory calculations at the B3LYP-D4/def2-TZVP level were carried out to rationalize the observed experimental findings.

Development of Novel Isatin-Tethered Quinolines as Anti-Tubercular Agents against Multi and Extensively Drug-Resistant Mycobacterium tuberculosis

We describe the design and synthesis of two isatin-tethered quinolines series (Q6a-h and Q8a-h), in connection with our research interest in developing novel isatin-bearing anti-tubercular candidates. In a previous study, a series of small molecules bearing a quinoline-3-carbohydrazone moiety was developed as anti-tubercular agents, and compound IV disclosed the highest potency with MIC value equal to 6.24 µg/mL. In the current work, we adopted the bioisosteric replacement approach to replace the 3,4,5-trimethoxy-benzylidene moiety in the lead compound IV with the isatin motif, a privileged scaffold in the TB drug discovery, to furnish the first series of target molecules Q6a-h. Thereafter, the isatin motif was N-substituted with either a methyl or benzyl group to furnish the second series Q8a-h. All of the designed quinoilne-isatin conjugates Q6a-h and Q8a-h were synthesized and then biologically assessed for anti-tubercular actions towards drug-susceptible, MDR, and XDR strains. Superiorly, the N-benzyl-bearing compound Q8b possessed the best activities against the examined M. tuberculosis strains with MICs equal 0.06, 0.24, and 1.95 µg/mL, respectively.

Thiophene-containing compounds with antimicrobial activity

Thiophene, as a member of the group of five-membered heterocycles containing one heteroatom, is one of the simplest heterocyclic systems. Many synthetic strategies allow the accurate positioning of various functionalities onto the thiophene ring. This review provides a comprehensive, systematic and detailed account of the developments in the field of antimicrobial compounds featuring at least one thiophene ring in their structure, over the last decade.

Sulfonamide-salicylaldehyde imines active against methicillin- and trimethoprim/sulfonamide-resistant Staphylococci

Background: Increasing resistance has resulted in an urgent need for new antimicrobial drugs. A systematic me-too approach was chosen to modify clinically used sulfonamides to obtain their imines. Methods & results: Twenty-five compounds were synthesized and evaluated for their antibacterial activity. The most active compounds were also investigated against methicillin- and trimethoprim/sulfamethoxazole (SMX)-resistant Gram-positive species. Staphylococci shared the highest susceptibility including resistant strains with minimum inhibitory concentrations from 3.91 μM (≥2.39 μg ml^-1). Crucially, the compounds inhibit MRSA and trimethoprim/SMX-resistant Staphylococci without any cross-resistance. Modification of parent sulfonamides turned a bacteriostatic effect into a bactericidal effect. Toxicity for HepG2 and hemolytic properties were also determined. Conclusions: The presence of a dihalogenated salicylidene moiety is required for optimal activity. Based on toxicity, promising derivatives for further investigation were identified.

Synthesis and Biological Activity of N-(arylsulfonyl) Valine Hydrazones and Assistance of NMR Spectroscopy for Definitive 3D Structure

Background:

Hydrazide-hydrazones constitute an important class of compounds for new drug development. In this study, a series of 39 new acylhydrazones (3-41), derived from (2S)-3-methyl- 2-[[(4-methylphenyl)sulfonyl]amino]butanoic acid hydrazide were synthesized with further aim to achieve biologically active acylhydrazones carrying an amino acid side chain.

Methods:

Compounds 3-41 were synthesized by microwave-assisted method. All synthesized compounds have been tested for their anti-HIV activity compound 21 was subjected to a new set of 2DNMR analysis for the characterization of the isomers in solution and determination of its 3D structure.

Results:

The IC50 values for compounds 2-40 were found between >125-10.90 µg/ml against HIV- 1(IIIB) and HIV-2(ROD) strains in MT-4 cells. Compounds 3, 6, 10, 12, 23, 24, 27, 32, and 37 with CC50 values between 10.90-14.50 µg/ml were selected to evaluate for their antileukemia activity. IC50 values for these mentioned compounds were found as >100μM on human chronic myelogenous leukemia, K562 cell line.

Conclusion:

Some compounds with IC50 values between 10.90-14.50 μg/ml will be of benefit in the development of novel leads.

Current development of 5-nitrofuran-2-yl derivatives as antitubercular agents

Pulmonary tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (MTB) and still remains one of the foremost fatal infectious diseases, infecting nearly a third of the worldwide population. The emergencies of multidrug-resistant and extensively drug-resistant tuberculosis (MDR and XDR-TB) prompt the efforts to deliver potent and novel anti-TB drugs. Research aimed at the development of new anti-TB drugs based on nitrofuran scaffold led to the identification of several candidates that were effective against actively growing as well as latent mycobacteria with unique modes of action. This review focuses on the recent advances in nitrofurans that could provide intriguing potential leads in the area of anti-TB drug discovery.

Novel 6-Phenylnicotinohydrazide Derivatives: Design, Synthesis and Biological Evaluation as a Novel Class of Antitubercular and Antimicrobial Agents

In our ongoing efforts to develop potent antitubercular agents based on the 6-phenylnicotinohydrazide, herein we report the design, synthesis and biological evaluation of three sets of 6-phenylnicotinohydrazide derivatives 8a-g, 12 and 16a, b. The designed compounds were synthesized and in vitro evaluated for their antitubercular activity. In addition, their antifungal and antibacterial activities were evaluated as well. The nicotinohydrazide class displayed different levels of antimicrobial activity and possessed a distinctive pattern of selectivity against the tested microorganisms. However, the 2,6-dichlorobenzylidene counterpart 8b emerged as the most active one in this study, with superior antimycobacterial activity (minimum inhibitory concentration (MIC)=3.90 µg/mL) and potent broad-spectrum antimicrobial activities with MIC range of 0.24-1.95 µg/mL. The structure-activity relationship for such nicotinohydrazides has been established. Further, the cytotoxicity of the most active antitubercular compounds 8b, d and g were tested against the normal breast cells WI-38; none of them displayed significant cytotoxic effect, thereby providing a good therapeutic index.

Synthesis and biological evaluation of 2-aminothiazole-thiazolidinone conjugates as potential antitubercular agents

AIM

Mycobacterium tuberculosis, which causes tuberculosis, continues to infect millions of the global population, resulting in 1.8 million deaths worldwide in 2015.

METHODOLOGY

Hybrids of 2-amino-4-methylthiazole bearing 5-acetyl/5-ethyl carboxylate functionality with 5-arylidene thiazolidinone moiety (6a-k and 9a-d) were synthesized and screened for antitubercular and antimicrobial activities.

RESULTS & DISCUSSION

5-ethyl carboxylate derivative 6k revealed half antitubercular activity (minimal inhibitory concentration = 1.56 μg/ml) than the acetyl analog 6c (minimal inhibitory concentration = 0.78 μg/ml), however, it exhibited more potent broad spectrum antibacterial and antifungal activities in addition to its excellent safety profile with high selectivity toward M. tuberculosis over normal human lung cells. Collectively, these data suggested that compound 6k can be considered as an ideal lead compound for further optimization.

Synthesis and Fluorescent Behaviour of 2-Aryl-4,5-dihydro-1H-1,2,4-triazoles

A series of new 4,5-dihydro-1H-1,2,4-triazoles was synthesized from amidrazones and acetylenedicarboxylic acid esters in the presence of pyridine in toluene. The synthesized compounds were characterized by ¹H, ¹³C NMR, FT-IR spectral analyses and XRD data. Optical studies revealed that most of the compounds reported here exhibited emission of blue or green-yellow light upon irradiation in acetone and showed Stokes shifts in the region of 70-96 nm and quantum yields of up to 45%. The interpretation of the experimental findings was supported by state-of-the-art quantum mechanical calculations.

Synthesis, Biological Evaluation and Molecular Docking of Certain Sulfones as Potential Nonazole Antifungal Agents

We reported herein the synthesis, antifungal activity, docking and in silico ADME prediction studies of four novel series of sulfones 6a–f, 8a–c, 10a–f and 12a–c. All the newly synthesized sulfones were tested against four strains of Candida (including fluconazole-resistant Candida), two strains of Aspergillus, two dermatophytic fungi (Trichophytons mentagrophyte and Microsporum canis) and Syncephalastrum sp. with fluconazole as a reference drug. In general, compounds 8a and 10b showed selective and potent anticandidal activity (MIC: 0.19–0.81 µM) relative to fluconazole (MIC = 1.00 µM). Furthermore, 10e and 12a elicited a remarkable and selective antifungal activity against Aspergillus sp. and the dermatophytic fungi (MIC: 0.16–0.79 µM) relative to fluconazole (MIC: 2–2.6 µM). Moreover, the docking results of the sulfones 6a, 8a, 10a and 10b at the active site of CYT P450 14α-sterol demethylase showed a comparable binding interaction (interaction Energy = −34.87 to −42.43 kcal/mol) with that of fluconazole (IE = −40.37 kcal/mol).