Design, synthesis, anti-mycobacterial activity, molecular docking and ADME analysis of spiroquinoxaline-1,2,4-oxadiazoles via [3 + 2] cycloaddition reaction under ultrasound irradiation

The development of anti-tuberculosis (anti-TB) drugs has become a challenging task in medicinal chemistry. This is because Mycobacterium tuberculosis (TB), the pathogen that causes tuberculosis, has an increasing number of drug-resistant strains, and existing medication therapies are not very effective. This resistance significantly demands new anti-TB drug profiles. Here, we present the design and synthesis of a number of hybrid compounds with previously known anti-mycobacterial moieties attached to quinoxaline, quinoline, tetrazole, and 1,2,4-oxadiazole scaffolds. A convenient ultrasound methodology was employed to attain spiroquinoxaline-1,2,4-oxadiazoles via [3 + 2] cycloaddition of quinoxaline Schiff bases and aryl nitrile oxides at room temperature. This approach avoids standard heating and column chromatography while producing high yields and shorter reaction times. The target compounds 3a-p were well-characterized, and their in vitro anti-mycobacterial activity (anti-TB) was evaluated. Among the screened compounds, 3i displayed promising activity against the Mycobacterium tuberculosis cell line H37Rv, with an MIC99 value of 0.78 µg/mL. However, three compounds (3f, 3h, and 3o) exhibited potent activity with MIC99 values of 6.25 µg/mL. To further understand the binding interactions, the synthesized compounds were docked against the tuberculosis protein 5OEQ using in silico molecular docking. Moreover, the most active compounds were additionally tested for their cytotoxicity against the RAW 264.7 cell line, and the cytotoxicity of compounds 3f, 3h, 3i, and 3o was 27.3, 28.9, 26.4, and 30.2 µg/mL, respectively. These results revealed that the compounds 3f, 3h, 3i, and 3o were less harmful to humans. Furthermore, the synthesized compounds were tested for ADME qualities, and the results suggest that this series is useful for producing innovative and potent anti-tubercular medicines in the future.

Design, Synthesis, Antifungal Evaluation, Structure-Activity Relationship (SAR) Study, and Molecular Docking of Novel Spirotryprostatin A Derivatives

Phytopathogenic fungi cause plant diseases and economic losses in agriculture. To efficiently control plant pathogen infections, a total of 19 spirotryprostatin A derivatives and 26 spirooxindole derivatives were designed, synthesized, and tested for their antifungal activity against ten plant pathogens. Additionally, the intermediates of spirooxindole derivatives were investigated, including proposing a mechanism for diastereoselectivity and performing amplification experiments. The bioassay results demonstrated that spirotryprostatin A derivatives possess good and broad-spectrum antifungal activities. Compound 4d exhibited excellent antifungal activity in vitro, equal to or higher than the positive control ketoconazole, against Helminthosporium maydis, Trichothecium roseum, Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium graminearum, Alternaria brassicae, Alternaria alternate, and Fusarium solan (MICs: 8-32 µg/mL). Compound 4k also displayed remarkable antifungal activity against eight other phytopathogenic fungi, including Fusarium oxysporium f. sp. niveum and Mycosphaerella melonis (MICs: 8-32 µg/mL). The preliminary structure-activity relationships (SARs) were further discussed. Moreover, molecular docking studies revealed that spirotryprostatin A derivatives anchored in the binding site of succinate dehydrogenase (SDH). Therefore, these compounds showed potential as natural compound-based chiral fungicides and hold promise as candidates for further enhancements in terms of structure and properties.

Chemo-/Regio-Selective Synthesis of Novel Functionalized Spiro[pyrrolidine-2,3'-oxindoles] under Microwave Irradiation and Their Anticancer Activity

A novel series of nitrostyrene-based spirooxindoles were synthesized via the reaction of substituted isatins 1a-b, a number of α-amino acids 2a-e and (E)-2-aryl-1-nitroethenes 3a-e in a chemo/regio-selective manner using [3+2] cycloaddition (Huisgen) reaction under microwave irradiation conditions. The structure elucidation of all the synthesized spirooxindoles were done using 1H and 13C NMR and HRMS spectral analysis. The single crystal X-ray crystallographic study of compound 4l was used to assign the stereochemical arrangements of the groups around the pyrrolidine ring in spiro[pyrrolidine-2,3'-oxindoles] skeleton. The in vitro anticancer activity of spiro[pyrrolidine-2,3'-oxindoles] analogs 4a-w against human lung (A549) and liver (HepG2) cancer cell lines along with immortalized normal lung (BEAS-2B) and liver (LO2) cell lines shows promising results. Out of the 23 synthesized spiro[pyrrolidine-2,3'-oxindoles], while five compounds (4c, 4f, 4m, 4q, 4t) (IC50 = 34.99-47.92 µM; SI = 0.96-2.43) displayed significant in vitro anticancer activity against human lung (A549) cancer cell lines, six compounds (4c, 4f, 4k, 4m, 4q, 4t) (IC50 = 41.56-86.53 µM; SI = 0.49-0.99) displayed promising in vitro anticancer activity against human liver (HepG2) cancer cell lines. In the case of lung (A549) cancer cell lines, these compounds were recognized to be more efficient and selective than standard reference artemisinin (IC50 = 100 µM) and chloroquine (IC50 = 100 µM; SI: 0.03). However, none of them were found to be active as compared to artesunic acid [IC50 = 9.85 µM; SI = 0.76 against lung (A549) cancer cell line and IC50 = 4.09 µM; SI = 2.01 against liver (HepG2) cancer cell line].

Synthesis and identification of new sacubitril derivatives as lead compounds for antibacterial, antifungal and antitubercular (TB) activities against dormant tuberculosis

We identified twenty-two new sacubitril derivatives (5a-v) as lead compounds for various biologically active targets. These compounds were synthesized by reacting an intermediate compound (2R,4S)-5-([1,1'-biphenyl]-4-yl)-4-(amino)-2-methylpentanoic acid ethyl ester hydrochloride with respective carboxylic acid (RCOOH). The molecular structures of all the newly synthesized compounds were determined by 1H and 13C NMR, ESI mass spectrometry, FTIR spectroscopy, and CHN analysis. Moreover, compound 5n was characterized by a single-crystal X-ray diffraction (SXRD) study to confirm the structure obtained from spectral data. All these compounds were screened for various biological functions such as antifungal, antibacterial, and anti-TB activities. Among these twenty-two compounds (5a-v), some exhibited good to moderate anti-bacterial properties. Similarly, some compounds showed moderate anti-TB and antifungal activities. In addition, the anti-TB activity of compound 5q was estimated against M. tuberculosis in a nutrient starvation model (NSM). Similarly, toxicity was examined against RAW 264.7 cells. These biological activity studies were also correlated with molecular docking studies.

Design and synthesis of novel quinazolinyl-bisspirooxindoles as potent anti-tubercular agents: an ultrasound-promoted methodology

The essential need for the potent anti-tubercular (anti-TB) agents with high selectivity and safety profile prompted us to synthesize a new series of quinazolinyl-bisspirooxindoles. The title compounds were synthesized by one-pot multicomponent [3 + 2] cycloaddition reaction under ultrasonication. Further, in vitro anti-TB activity was evaluated against Mycobacterium tuberculosis H37Rv. Among the screened compounds, two compounds (4q and 4x) showed potent activity with MIC value 1.56 µg/mL and four compounds exhibited significant activity (MIC = 3.125 µg/mL), and also cytotoxicity studies against RAW 264.7 cell lines reveal that most active compounds were less toxic to humans. In addition, in order to demonstrate the inhibitory properties, molecular docking studies were carried out and the results showed that the target compounds have good binding energy and better binding affinity within the active pocket, thus these compounds may consider to be as potent inhibitors toward selective targets.

Emerging impact of triazoles as anti-tubercular agent

Tuberculosis, a disease of poverty is a communicable infection with a reasonably high mortality rate worldwide. 10 Million new cases of TB were reported with approx 1.4 million deaths in the year 2019. Due to the growing number of drug-sensitive and drug-resistant tuberculosis cases, there is a vital need to develop new and effective candidates useful to combat this deadly disease. Despite tremendous efforts to identify a mechanism-based novel antitubercular agent, only a few have entered into clinical trials in the last six decades. In recent years, triazoles have been well explored as the most valuable scaffolds in drug discovery and development. Triazole framework possesses favorable properties like hydrogen bonding, moderate dipole moment, enhanced water solubility, and also the ability to bind effectively with biomolecular targets of M. tuberculosis and therefore this scaffold displayed excellent potency against TB. This review is an endeavor to summarize an up-to-date innovation of triazole-appended hybrids during the last 10 years having potential in vitro and in vivo antitubercular activity with structure activity relationship analysis. This review may help medicinal chemists to explore the triazole scaffolds for the rational design of potent drug candidates having better efficacy, improved selectivity and minimal toxicity so that these hybrid NCEs can effectively be explored as potential lead to fight against M. tuberculosis.

Design, synthesis and anticancer activity of novel pyrimidine and pyrimidine-thiadiazole hybrid glycosides

New 1,3,4-thiadiazole thioglycosides linked to substituted pyrimidines were synthesized via glycosylation of 1,3,4-thiadiazole thiol compounds. Also, novel 1,2,3-triazole derivatives linked to carbohydrate units were prepared using the standard click chemistry conditions employing the Cu(I)-catalyzed azide-alkyne cycloaddition of substituted-aryl-azides with a selection of alkyne-functionalized sugars. The chemical structures of the new derivatives were verified using various spectroscopic techniques, such as IR, ¹H NMR, ¹³C NMR and elemental analyses. The cytotoxic activities of the prepared compounds were investigated in vitro against human liver cancer (HepG-2) and human breast adenocarcinoma (MCF7) cell lines. In addition, the biological evaluation of the new compounds involved the investigation of their effects on a human normal retinal pigmented epithelial cell line (RPE1) using the MTT assay.

An overview of spirooxindole as a promising scaffold for novel drug discovery

Introduction: Spirooxindole, a unique and versatile scaffold, has been widely studied in some fields such as pharmaceutical chemistry and synthetic chemistry. Especially in the application of medicine, quite a few compounds featuring spirooxindole motif have displayed excellent and broad pharmacological activities. Many identified candidate molecules have been used in clinical trials, showing promising prospects.Areas covered: This article offers an overview of different applications and developments of spirooxindoles (including the related natural products and their derivatives) in the process of drug innovation, including such as in anticancer, antimicrobial, anti-inflammatory, analgesic, antioxidant, antimalarial, and antiviral activities. Furthermore, the crucial structure-activity relationships, molecular mechanisms, pharmacokinetic properties, and main synthetic methods of spirooxindoles-based derivatives are also reviewed.Expert opinion: Recent progress in the biological activity profiles of spirooxindole derivatives have demonstrated their significant position in present-day drug discovery. Furthermore, we believe that the multidirectional development of novel drugs containing this core scaffold will continue to be the research hotspot in medicinal chemistry in the future.

Design, Synthesis, and Antimicrobial Activities of 1,2,3-Triazole Glycoside Clickamers

Bacterial resistance remains a significant threat and a leading cause of death worldwide, despite massive attempts to control infections. In an effort to develop biologically active antibacterial and antifungal agents, six novel aryl-substituted-1,2,3-triazoles linked to carbohydrate units were synthesized through the Cu(I)-catalyzed azide-alkyne cycloaddition CuAAC of substituted-arylazides with a selection of alkyne-functionalized sugars. The chemical structures of the new derivatives were verified using different spectroscopic techniques. The novel clicked 1,2,3-triazoles were evaluated for in vitro antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, and the obtained results were compared with the activity of the reference antibiotic "Ampicillin". Likewise, in vitro antifungal activity of the new 1,2,3-triazoles was investigated against Candida albicans and Aspergillus niger using "Nystatin" as a reference drug. The results of the biological evaluation pointed out that Staphylococcus aureus was more susceptible to all of the tested compounds than other examined microbes. In addition, some tested compounds exhibited promising antifungal activity.