Stereoselective Unsymmetrical 1,1-Diborylation of Alkynes with a Neutral sp2 -sp3 Diboron Reagent

The incorporation of two distinct boryl groups at the same carbon center in organic molecules has attracted growing research interest due to its potential for facilitating controlled, precise synthesis through stepwise dual carbon-boron bond transformations. Here we report a method to access unsymmetrical 1,1-diborylalkene (UDBA) stereoselectively via the reaction of readily available alkynes with a neutral sp2 -sp3 diboron reagent (NHC)BH2 -Bpin (NHC=N-heterocyclic carbene). Attributing to the chemically easily distinguishable nature of the sp2 and sp3 boryl moieties, controllable stepwise derivatization of the resultant UDBAs is realized. This process leads to various multifunctionalized olefins and organoborons, such as acylboranes, which are difficult to prepare by other methods.

Tetrahydrobenzo[h]quinoline derivatives as a novel chemotype for dual antileishmanial-antimalarial activity graced with antitubercular activity: Design, synthesis and biological evaluation

Derivatives with tetrahydrobenzo[h]quinoline chemotype were synthesized via one-pot reactions and evaluated for their antileishmanial, antimalarial and antitubercular activities. Based on a structure-guided approach, they were designed to possess antileishmanial activity through antifolate mechanism, via targeting Leishmania major pteridine reductase 1 (Lm-PTR1). The in vitro antipromastigote and antiamastigote activity are promising for all candidates and superior to the reference miltefosine, in a low or sub micromolar range of activity. Their antifolate mechanism was confirmed via the ability of folic and folinic acids to reverse the antileishmanial activity of these compounds, comparably to Lm-PTR1 inhibitor trimethoprim. Molecular dynamics simulations confirmed a stable and high potential binding of the most active candidates against leishmanial PTR1. For the antimalarial activity, most of the compounds exhibited promising antiplasmodial effect against P. berghei with suppression percentage of up to 97.78%. The most active compounds were further screened in vitro against the chloroquine resistant strain P. falciparum, (RKL9) and showed IC50 value range of 0.0198-0.096 μM, compared to IC50 value of 0.19420 μM for chloroquine sulphate. Molecular docking of the most active compounds against the wild-type and quadruple mutant pf DHFR-TS structures rationalized the in vitro antimalarial activity. Some candidates showed good antitubercular activity against sensitive Mycobacterium tuberculosis in a low micromolar range of MIC, compared to 0.875 μM of isoniazid. The top active ones were further tested against a multidrug-resistant strain (MDR) and extensively drug-resistant strain (XDR) of Mycobacterium tuberculosis. Interestingly, the in vitro cytotoxicity test of the best candidates displayed high selectivity indices emphasizing their safety on mammalian cells. Generally, this work introduces a fruitful matrix for new dual acting antileishmanial-antimalarial chemotype graced with antitubercular activity. This would help in tackling drug-resistance issues in treating some Neglected Tropical Diseases.

Diaryl ether derivative inhibits GPX4 expression levels to induce ferroptosis in thyroid cancer cells

Papillary thyroid carcinoma contributes to about 80% of the total thyroid cancer cases. BRAFV600E is a frequently occurring mutation in PTCs. Although several BRAF inhibitors are available, many thyroid cancer patients acquire resistance to BRAF inhibitors. Therefore, new targets and drugs need to be identified as therapies. Ferroptosis is a recently discovered type of cell death, and inhibiting glutathione peroxidase 4 (GPX4) using small molecules was found to trigger ferroptosis. But it is unknown whether inhibiting GPX4 renders thyroid cancer cells susceptible to ferroptosis. To identify novel GPX4 inhibitors, we focused on our previously reported cohort of diaryl ether and dibenzoxepine molecules. In this study, we asked whether diaryl ether and dibenzoxepine derivatives trigger ferroptosis in thyroid cancer cells. To answer this question, we screened diaryl ether and dibenzoxepine derivatives in cell-based assays and performed mechanism of action studies. We found that a diaryl ether derivative, 16 decreased thyroid cell proliferation and triggered ferroptosis by inhibiting GPX4 expression levels. Molecular modeling and dynamics simulations showed that 16 binds to the active site of GPX4. Upon deciphering the mode of 16-induced ferroptosis, we found that 16 treatments decrease mitochondrial polarization and reduce mitochondrial respiration similar to a ferroptosis inducer, RSL3. We conclude that the diaryl ether derivative, 16 inhibits GPX4 expression levels to induce ferroptosis in thyroid cancer cells. Based on our observations, we suggest that 16 can be lead-optimized and developed as a ferroptosis-inducing agent to treat thyroid cancers.

Medicinal chemistry perspectives of 1,2,3,4-tetrahydroisoquinoline analogs - biological activities and SAR studies

Isoquinoline alkaloids are a large group of natural products in which 1,2,3,4-tetrahydroisoquinolines (THIQ) form an important class. THIQ based natural and synthetic compounds exert diverse biological activities against various infective pathogens and neurodegenerative disorders. Due to these reasons, the THIQ heterocyclic scaffold has garnered a lot of attention in the scientific community which has resulted in the development of novel THIQ analogs with potent biological activity. The present review provides a much-needed update on the biological potential of THIQ analogs, their structural-activity relationship (SAR), and their mechanism of action. In addition, a note on commonly used synthetic strategies for constructing the core scaffold has also been discussed.

Synthesis of new selective cytotoxic ricinine analogues against oral squamous cell carcinoma

Sixteen new analogues were synthesized from ricinine and tested alongside with seven known analogues for their cytotoxic activity against oral cancer (SAS cells) and normal epithelial cells (L132 cells). In contrast to 5-FU, the synthesized ricinine analogues did not show toxicity to normal cells. However, some of them inhibited the proliferation of oral cancer cells at 25 µM as evident from the MTT assay results. Ricinine analogue (19) was shown to be the most active derivative (69.22% inhibition). Potential targets involved in the oral cancer inhibitory activity of compound 19 were investigated using in-silico studies and western blot analysis. PTP1B was predicted to be a target for ricinine using reverse docking approach. This prediction was confirmed by western blot analysis that revealed the downregulation of PTP1B protein by compound 19. Moreover, it showed downregulation of COX-2 which is also extensively expressed in oral cancer.

Synthesis and biological evaluation of (1,2,4)triazole[4,3-a]pyridine derivatives as potential therapeutic agents for concanavalin A-induced hepatitis

A series of (1,2,4)triazole[4,3-a]pyridine (TZP) derivatives have been designed and synthesized. Compound 8d was identified as having the most potent inhibitory activity on NO release in response to lipopolysaccharide (LPS) stimulation and inhibition of the migration induced by MCP-1 protein on RAW264.7 macrophages. Based on the screening data, an immunofluorescence assay and a real-time qPCR assay were conducted, indicating that compound 8d suppressed NF-κB p65 translocation and expression of inflammatory genes by concanavalin A (Con A)-induced RAW264.7 macrophages. More importantly, 8d also exhibited potent efficacy, alleviating Con A-induced hepatitis by downregulating the levels of plasma alanine transaminase (ALT), aspartate transaminase (AST) and inflammatory infiltration in a mouse autoimmune hepatitis (AIH) model. In addition, the flow cytometry (FCM) data showed that compound 8d inhibited the accumulation of MDSCs in the liver of Con A-induced mice. These findings raise the possibility that compound 8d might serve as a potential agent for the treatment of AIH.

Potentials of Diphenyl Ether Scaffold as a Therapeutic Agent: A Review

Diphenyl ethers (DPE) and its analogs have exhibited excellent potential for therapeutic and industrial applications. Since the 19th century, intensive research is perpetuating on the synthetic routes and biological properties of DPEs. Few well-known DPEs are Nimesulide, Fenclofenac, Triclosan, Sorafenib, MK-4965, and MK-1439 which have shown the potential of this moiety as a lead scaffold for different pharmacological properties. In this review, we recapitulate the diverse synthetic route of DPE moiety inclusive of merits and demerits over the classical synthetic route and how this moiety sparked an interest in researchers to discern the SAR (Structure Activity Relationship) for the development of diversified biological properties of DPEs such as antimicrobial, antifungal, antiinflammatory & antiviral activities.

Design, synthesis and anti-HIV-1 RT evaluation of 2-(benzyl(4-chlorophenyl)amino)-1-(piperazin-1-yl)ethanone derivatives

In this study, using molecular hybridization approach, fourteen novel 2-(benzyl(4-chlorophenyl)amino)-1-(piperazin-1-yl)ethanone derivatives (7a-n) were designed as inhibitor of HIV-1 RT. The binding affinity of the designed compounds with HIV-1 RT as well as their drug-likeness behavior was predicted using in-silico studies. All the designed compounds were synthesized, characterized and in-vitro evaluated for HIV-1 RT inhibitory activity, in which tested compounds displayed significant to weak potency against the selected target. Moreover, best active compounds of the series, 7k and 7m inhibited the activity of RT with IC₅₀ values 14.18 and 12.26μM respectively. Structure Activity Relationship (SAR) studies were also performed in order to predict the influence of substitution pattern on the RT inhibitory potency. Anti-HIV-1 and cytotoxicity studies of best five RT inhibitor (7a, 7d, 7k, 7L and 7m) revealed that, except compound 7d other compounds retained significant anti-HIV-1 potency with good safety index. Best scoring pose of compound 7m was analysed in order to predict its putative binding mode with wild HIV-1 RT.

1,6-Bis[(benzyloxy)methyl]uracil derivatives-Novel antivirals with activity against HIV-1 and influenza H1N1 virus

A series of 1,6-bis[(benzyloxy)methyl]uracil derivatives combining structural features of both diphenyl ether and pyridone types of NNRTIs were synthesized. Target compounds were found to inhibit HIV-1 reverse transcriptase at micro- and submicromolar levels of concentrations and exhibited anti-HIV-1 activity in MT-4 cell culture, demonstrating resistance profile similar to first generation NNRTIs. The synthesized compounds also showed profound activity against influenza virus (H1N1) in MDCK cell culture without detectable cytotoxicity. The lead compound of this assay appeared to exceed rimantadine, amantadine, ribavirin and oseltamivir carboxylate in activity. The mechanism of action of 1,6-bis[(benzyloxy)methyl]uracils against influenza virus is currently under investigation.

A facile one-pot multi-component synthesis of novel adamantine substituted imidazo[1,2-a]pyridine derivatives: identification and structure–activity relationship study of their anti-HIV-1 activity

A series of adamantine substituted imidazo[1,2-a]pyridine derivatives were developed through a one-pot multi-component Groebke–Blackburn–Bienaymé reaction, among them several compounds were identified to be the potent inhibitors against HIV-1 cells.

De-novo design, synthesis and evaluation of novel 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives as HIV-1 reverse transcriptase inhibitors

Background

Acquired Immune Deficiency Syndrome (AIDS) is the advanced stage of infection caused by Human Immunodeficiency Virus (HIV). HIV/AIDS had a great impact on society, both as an illness and as a source of discrimination. Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) are structurally diverse group of compounds which binds to Reverse Transcriptase (RT) enzyme of HIV. Like other anti-HIV drugs, long-term clinical effectiveness of approved NNRTIs has been hampered due to the rapid development of drug resistance. So, there is an urgent need to discover the NNRTIs, which can be effective against the drug sensitive as well as drug resistant strains of HIV-1 RT.

Results

Two series of novel thirty, 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline analogues (5a-o) and (8a-o) were designed and synthesized as inhibitor of HIV-1 reverse transcriptase. All the synthesized compounds were characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, mass spectroscopy and evaluated for in-vitro RT inhibitory activity. Among the tested compounds, eighteen compounds exhibited more than 50 % inhibition at tested 100 μM concentration, in which two compounds 8h and 8l showed promising inhibition (74.82 and 72.58 %) respectively. The preliminary structure–activity relationship (SAR) of the test compounds and docking studies of the two significantly active compounds 8h and 8l were performed to examine their putative binding with HIV-RT. Predicted physiochemical parameters of the synthesized compounds were within the acceptable range of drugable properties.

Conclusion

The results obtained from this investigation revealed that, the synthesized compounds (5a-o) and (8a-o) showed moderate to promising HIV-1 RT inhibition activity. The overall SAR studies can help in identification of further lead as well as in designing of newer potential inhibitor of HIV-1 RT.

Graphical Abstract

HIV-1 NNRTIs: structural diversity, pharmacophore similarity, and implications for drug design

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) nowadays represent very potent and most promising anti-AIDS agents that specifically target the HIV-1 reverse transcriptase (RT). However, the effectiveness of NNRTI drugs can be hampered by rapid emergence of drug-resistant viruses and severe side effects upon long-term use. Therefore, there is an urgent need to develop novel, highly potent NNRTIs with broad spectrum antiviral activity and improved pharmacokinetic properties, and more efficient strategies that facilitate and shorten the drug discovery process would be extremely beneficial. Fortunately, the structural diversity of NNRTIs provided a wide space for novel lead discovery, and the pharmacophore similarity of NNRTIs gave valuable hints for lead discovery and optimization. More importantly, with the continued efforts in the development of computational tools and increased crystallographic information on RT/NNRTI complexes, structure-based approaches using a combination of traditional medicinal chemistry, structural biology, and computational chemistry are being used increasingly in the design of NNRTIs. First, this review covers two decades of research and development for various NNRTI families based on their chemical scaffolds, and then describes the structural similarity of NNRTIs. We have attempted to assemble a comprehensive overview of the general approaches in NNRTI lead discovery and optimization reported in the literature during the last decade. The successful applications of medicinal chemistry strategies, crystallography, and computational tools for designing novel NNRTIs are highlighted. Future directions for research are also outlined.