Bioactive 1,2,3-Triazoles: An Account on their Synthesis, Structural Diversity and Biological Applications

The triazole heterocycle is a privileged scaffold in medicinal chemistry, since its structure is present in a large number of biologically active molecules, including several drugs currently in the market. Due to their vast applications, a wide variety of methods are described for their preparation, such as the 1,3-dipolar cycloaddition and processes involving diazo compounds and diazo transfer reactions. Considering the significant number of contributions from our research group to this chemistry in recent decades, in this account we discuss both the development of new methods for the synthesis of 1,2,3-triazoles and the preparation of new triazole-functionalized biologically active molecules using classical approaches.

Drug repurposing for the treatment of COVID-19: Pharmacological aspects and synthetic approaches

In December 2019, a new variant of SARS-CoV emerged, the so-called acute severe respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus causes the new coronavirus disease (COVID-19) and has been plaguing the world owing to its unprecedented spread efficiency, which has resulted in a huge death toll. In this sense, the repositioning of approved drugs is the fastest way to an effective response to a pandemic outbreak of this scale. Considering these facts, in this review we provide a comprehensive and critical discussion on the chemical aspects surrounding the drugs currently being studied as candidates for COVID-19 therapy. We intend to provide the general chemical community with an overview on the synthetic/biosynthetic pathways related to such molecules, as well as their mechanisms of action against the evaluated viruses and some insights on the pharmacological interactions involved in each case. Overall, the review aims to present the chemical aspects of the main bioactive molecules being considered to be repositioned for effective treatment of COVID-19 in all phases, from the mildest to the most severe.

4-Oxoquinoline Derivatives as Antivirals: A Ten Years Overview

4-Oxoquinoline derivatives constitute an important family of biologically important substances, associated with different bioactivities, which can be synthesized by different synthetic methods, allowing the design and preparation of libraries of substances with specific structural variations capable of modulating their pharmacological action. Over the last years, these substances have been extensively explored by the scientific community in efforts to develop new biologically active agents, with greater efficiency for the treatment of a variety of diseases. Viral infections have been one of the targets of these studies, although to a lesser extent than other diseases such as cancer and bacterial infections. Nevertheless, the literature provides examples that corroborate with the fact that these substances may act on different pharmacological targets in different viral pathogens. This review provides a compilation of some of the major studies published in recent years showing the discovery and/or development of new antiviral oxoquinoline agents, highlighting, whenever possible, their mechanisms of action.

Study on the regioselectivity of the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide

4-Oxoquinolines are a class of organic substances of great importance in medicinal chemistry, due to their biological and synthetic versatility. N-1-Alkylated-4-oxoquinoline derivatives have been associated with different pharmacological activities such as antibacterial and antiviral. The presence of a carboxamide unit connected to carbon C-3 of the 4-oxoquinoline core has been associated with various biological activities. Experimentally, the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide occurs at the nitrogen of the oxoquinoline group, in a regiosselective way. In this work, we employed DFT methods to investigate the regiosselective ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide, evaluating its acid/base behavior and possible reaction paths.

Synthesis of new porphyrin/4-quinolone conjugates and evaluation of their efficiency in the photoinactivation of Staphylococcus aureus

The synthesis of new porphyrin/4-quinolone conjugates and their evaluation as potential photosensitizers in the photoinactivation of Staphylococcus aureus is described.

Synthesis, cytotoxicity and mechanistic evaluation of 4-oxoquinoline-3-carboxamide derivatives: finding new potential anticancer drugs

As part of a continuing search for new potential anticancer candidates, we describe the synthesis, cytotoxicity and mechanistic evaluation of a series of 4-oxoquinoline-3-carboxamide derivatives as novel anticancer agents. The inhibitory activity of compounds 10–18 was determined against three cancer cell lines using the MTT colorimetric assay. The screening revealed that derivatives 16b and 17b exhibited significant cytotoxic activity against the gastric cancer cell line but was not active against a normal cell line, in contrast to doxorubicin, a standard chemotherapeutic drug in clinical use. Interestingly, no hemolytical activity was observed when the toxicity of 16b and 17b was tested against blood cells. The in silico and in vitro mechanistic evaluation indicated the potential of 16b as a lead for the development of novel anticancer agents against gastric cancer cells.

Antivenom effects of 1,2,3-triazoles against Bothrops jararaca and Lachesis muta snakes

Snake venoms are complex mixtures of proteins of both enzymes and nonenzymes, which are responsible for producing several biological effects. Human envenomation by snake bites particularly those of the viperid family induces a complex pathophysiological picture characterized by spectacular changes in hemostasis and frequently hemorrhage is also seen. The present work reports the ability of six of a series of 1,2,3-triazole derivatives to inhibit some pharmacological effects caused by the venoms of Bothrops jararaca and Lachesis muta. In vitro assays showed that these compounds were impaired in a concentration-dependent manner, the fibrinogen or plasma clotting, hemolysis, and proteolysis produced by both venoms. Moreover, these compounds inhibited biological effects in vivo as well. Mice treated with these compounds were fully protected from hemorrhagic lesions caused by such venoms. But, only the B. jararaca edema-inducing activity was neutralized by the triazoles. So the inhibitory effect of triazoles derivatives against some in vitro and in vivo biological assays of snake venoms points to promising aspects that may indicate them as molecular models to improve the production of effective antivenom or to complement antivenom neutralization, especially the local pathological effects, which are partially neutralized by antivenoms.

Complete and unambiguous assignments of 1H and 13C chemical shifts of new arylamino derivatives of ortho-naphthofuranquinones

Six new nor-beta-lapachones have been synthesized from reaction of 3-bromo-nor-beta-lapachone with arylamines. These derivatives have potent anticancer properties against several cell lines. Here, we report complete unambiguous assignments of (1)H and (13)C chemical shifts of the new compounds. The assignments were made using a combination of one- and two-dimensional NMR techniques ((1)H, (13)C, (1)H-(1)H COSY, (1)H-(13)C HSQC, and (1)H-(13)C HMBC).

Synthesis and anti-Trypanosoma cruzi activity of derivatives from nor-lapachones and lapachones

New naphthoquinone derivatives were synthesized and assayed against bloodstream trypomastigote forms of Trypanosoma cruzi, the etiological agent of Chagas' disease. The compounds were rationalized based on hybrid drugs and appear as important compounds against this parasite. From nor-lapachol were prepared five substituted ortho-naphthofuranquinones, a non-substituted para-naphthofuranquinone, a new oxyrane and an azide and from alpha-lapachone a new non-substituted para-naphthofuranquinone. Other five substituted ortho-naphthofuranquinones recently designed as cytotoxic, were also evaluated. The most active compounds were the ortho naphthofuranquinones 3-(4-methoxyphenylamino)-2,3-dihydro-2,2-dimethylnaphtho[1,2-b]furan-4,5-dione and 3-(3-nitrophenylamino)-2,3-dihydro-2,2-dimethylnaphtho[1,2-b]furan-4,5-dione with trypanocidal activity higher than that of benznidazole, the standard drug. The compounds were rationalized based on hybrid drugs and appear as important compounds against T. cruzi. The trypanocidal activity of these substances endowed with redox properties representing a good starting point for a medicinal chemistry program aiming the chemotherapy of Chagas' disease.

Synthesis and potent antitumor activity of new arylamino derivatives of nor-β-lapachone and nor-α-lapachone

Several arylamino derivatives of nor-beta-lapachone were synthesized in moderate to high yields and found to show very potent cytotoxicity against six neoplastic cancer cells: SF-295 (central nervous system), HCT-8 (colon), MDAMB-435 (breast), HL-60 (leukaemia), PC-3 (prostate), and B-16 (murine melanoma), with IC(50) below 1 microg/mL. Their cytotoxicities were compared to doxorubicin and with their synthetic precursors, beta-lapachone and nor-beta-lapachone. The activity against a normal murine fibroblast L-929 showed that some of the compounds were selective against cancer cells. The absence of hemolytic activity (EC(50)>200 microg/mL), performed with erythrocyte suspensions, suggests that the cytotoxicity of the compounds was not related to membrane damage of mouse erythrocytes. For comparison purposes, one isomeric compound based on nor-alpha-lapachone was also synthesized and showed lower activity than the related ortho-derivative. The modified arylamino quinones appear as interesting new lead compounds in anti-cancer drug development.

Naphthoquinoidal [1,2,3]-triazole, a new structural moiety active against Trypanosoma cruzi

[1,2,3]-Triazole derivatives of nor-beta-lapachone were synthesized and assayed against the infective bloodstream trypomastigote form of Trypanosoma cruzi, the etiological agent of Chagas disease. All the derivatives were more active than the original quinones, with IC(50)/1 day values in the range of 17 to 359 microM, the apolar phenyl substituted triazole 6 being the most active compound. These triazole derivatives of nor-beta-lapachone emerge as interesting new lead compounds in drug development for Chagas disease.

Synthesis and anti-HSV-1 activity of quinolonic acyclovir analogues

Several 1-[(2-hydroxy-ethoxy)methyl]-3-carbethoxy-4(1H)quinolones (2a-l) and l-[(2-hydroxy-ethoxy)methyl]-4(1H)quinolone-3-carboxylic acids (3a-j and 3l) were synthesized and 2a-j, 2l and 3a-j, 3l were evaluated against herpes simplex virus type 1 (HSV-1), employing a one-pot reaction: silylation of the desired quinolone (BSTFA 1% TMCS) followed by equimolar amount addition of 1,3-dioxolane, chlorotrimethylsilane and KI, at room temperature. The acyclonucleosides 2a-l were obtained in 40-77% yields. The esters 2a-j and 2l were subsequently converted into the corresponding hydroxyacids 3 in 40-70% yields. Attempts of hydrolysis of 2k produced only a mixture of degradation products. Antiviral activity of 2 and 3 on HSV-1 virus infection was assessed by the virus yield assay. Except for compounds 2i and 3e, the acyclonucleosides were found to reduce the virus yield by 70-99% at the concentration of 50 microM, being the acids, in general, more effective inhibitors than their corresponding esters. Compounds 3j and 2d exhibited antiviral activity against HSV-1 virus with EC50 of 0.7+/-0.04 and 0.8+/-0.09 microM, respectively. Both compounds were not toxic towards the Vero cell line.

Structure–activity relationships of novel inhibitors of glyceraldehyde-3-phosphate dehydrogenase

3D QSAR studies were performed on a library of 120 GAPDH inhibitors, including a series of coumarins, flavonoids, and nucleosides. The VolSurf method was successfully used to calculate surface descriptors for protein-ligand affinity and binding site of the enzyme. PCA/PLS analyses have permitted the evaluation of the structural features crucial for potency, selectivity, and favorable pharmacokinetic properties, and are important for the design of new ligands.

Antiplatelet properties of novel N-substituted-phenyl-1,2,3-triazole-4-acylhydrazone derivatives

This paper describes the design, synthesis and pharmacological evaluation of new N-acylhydrazone (NAH) compounds, belonging to the N-substituted-phenyl-1,2,3-triazole-4-acylhydrazone class (2a-p). Classical heteroaromatic ring bioisosterism strategies were applied to the previously reported N-phenylpyrazolyl-4-acylhydrazone derivative 1, elected as lead-compound due to its important anti-aggregating profile on arachidonic acid induced platelet aggregation (IC(50)=24+/-0.5 micro M), from which emerge this new series 2. These new compounds 2a-p were readily synthesized, characterized and tested on platelet aggregation assays induced by collagen (5 micro g/mL), ADP (5 micro M) and arachidonic acid (100 micro M) in rabbit citrated platelet-rich plasma. Compounds 2b, 2d, and 2h were found to be the most potent, exhibiting a significant antiplatelet activity on arachidonic acid- and collagen-induced platelet aggregation. In addition, these new antiplatelet agents are free of gastric ulcerogenic effect and presented discrete anti-inflammatory and analgesic properties. The N-para-chlorophenyltriazolyl-4-acylhydrazone compound 2h produced the highest inhibitory effect on collagen (IC(50)=21.6+/-0.4 micro M) and arachidonic acid-induced platelet aggregation (IC(50)=2.2+/-0.06 micro M), suggesting that the nature of the substituent on the phenyl ring of the N-heteroaromatic system of NAH moiety may be an important structural requirement for the improvement of antiplatelet activity, in comparison with lead-series 1.

Synthesis and antiviral evaluation of isatin ribonucleosides

A series of novel substituted isatin ribonucleosides 3b-3f were synthesized in good yields by a TMSOTf catalysed coupling reaction between the silylated nitrogenated base (1b-1f) and 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose (2). Isatin nucleoside 3a previously reported was also prepared using this method giving high yield. From the compounds tested, ribonucleoside 3f proved to be the most active one when assayed for antiviral activitiy on HSV-1 infected cells, leading to 66% of inhibition of virus yield. All the isatin derivatives tested did not inhibit HIV-1 Reverse Transcriptase (RT) activity.