Medicinal Chemistry - Volume 16, Issue 1, 2020

Background: Thiazole is a good nucleus owing to its various pharmaceutical applications. Thiazole containing compounds (thiazoles) have shown various biological activities like antioxidant, analgesic, antibacterial, anticancer, antiallergic, antihypertensive, antiinflammatory, antimalarial, antifungal and antipsychotic. The scaffold is present in more than 18 FDA approved drugs and also in more than 70 experimental drugs. Only a few reviews are available in the literature despite its great medicinal importance. During the course of time, this scaffold has been studied extensively for its antiviral activities and provided compounds with activity in the nM range. However, no focused review is available on the compilation of antiviral activities shown by this scaffold. Objective: In the present review, we have made an effort to compile antiviral literature of thiazoles reported from the year 2011 to till date. Methods: We searched the SciFinder database (excluding patent literature) with keywords like “antiviral”, “anti-HIV” and “virus”. Further filters were applied for the year of publication and keywords thiazole, reviews etc. to find relevant literature reported on the antiviral activities of thiazoles. Results: Nearly, 50 research articles were selected to compile and review the antiviral literature of thiazoles reported from the year 2011 to till date. Compounds 8, 25, 40, 62, 72, 73, 91, 112, 113, 131, 137, 175, 198, 200, 201 and 213 were reported in the literature with potent antiviral activity against CVB, SARS, RSV, HCV, HRV, VZV, TMV, FMDV, DENV, YFV, influenza virus, Junin virus, HIV-1, HSV, VV and EBV, respectively. Conclusion: There is further scope for the synthesis and evaluation of novel thiazole compounds by taking the most active compounds as lead structures. In conclusion, this review provides an overview of antiviral activities of thiazole compounds reported from the year 2011 to till date.

More than 10 million people around the world are afflicted by Neglected Tropical Diseases, such as Chagas Disease, Human African Trypanosomiasis, and Leishmania. These diseases mostly occur in undeveloped countries that suffer from a lack of economic incentive, research, and policy for new compound development. Sulfonamide moieties are effective scaffolds present in several compounds that are determinants to treat various diseases, principally neglected tropical diseases. This review article examines the contribution of these scaffolds in medicinal chemistry in the last five years, focusing on three trypanosomatid parasites: Trypanosoma cruzi, Trypanosoma brucei, and Leishmania ssp. We also present perspectives for their use in drug designs in an effort to contribute to new drug development. In addition, we consider the physicochemical parameters, whose molecules all presented according to Lipinski's rule. The correlation between the selective index and LogP was evaluated, showing that sulfonamide derivatives can act differently against each trypanosomatid parasite. Moreover, the approaches of novel drugs and technologies are very important for the eventual drug discovery against trypanosomatid diseases.

Background: Leishmaniasis is a neglected disease that does not have adequate treatment. It affects around 12 million people around the world and is classified as a neglected disease by the World Health Organization. In this context, strategies to obtain new, more active and less toxic drugs should be stimulated. Sources of natural products combined with synthetic and chemoinformatic methodologies are strategies used to obtain molecules that are most likely to be effective against a specific disease. Computer-Aided Drug Design has become an indispensable tool in the pharmaceutical industry and academia in recent years and has been employed during various stages of the drug design process. Objectives: Perform structure- and ligand-based approaches, synthesize and characterize some compounds with materials available in our laboratories to verify the method’s efficiency. Methods: We created a database with 33 cyclic imides and evaluated their potential anti- Leishmanial activity (L. amazonensis and L. donovani) through ligand- and structure-based virtual screening. A diverse set selected from ChEMBL databanks of 818 structures (L. donovani) and 722 structures (L. amazonensis), with tested anti-Leishmanial activity against promastigotes forms, were classified according to pIC50 values to generate and validate a Random Forest model that shows higher statistical indices values. The structures of four different L. donovani enzymes were downloaded from the Protein Data Bank and the imides’ structures were submitted to molecular docking. So, with available materials and technical feasibility of our laboratories, we have synthesized and characterized seven compounds through cyclization reactions between isosafrole and maleic anhydride followed by treatment with different amines to obtain new cyclic imides to evaluate their anti-Leishmanial activity. Results: In silico study allowed us to suggest that the cyclic imides 516, 25, 31, 24, 32, 2, 3, 22 can be tested as potential multitarget molecules for leishmanial treatment, presenting activity probability against four strategic enzymes (Topoisomerase I, N-myristoyltransferase, cyclophilin and Oacetylserine sulfhydrylase). The compounds synthesized and tested presented pIC50 values less than 4.7 for Leishmania amazonensis. Conclusion: After combined approach evaluation, we have synthesized and characterized seven cyclic imides by IR, 1H NMR, 13C-APT NMR, COSY, HETCOR and HMBC. The compounds tested against promastigote forms of L. amazonensis presented pIC50 values less than 4.7, showing that our method was efficient in predicting true negative molecules.

Background: EGFR is a clinically approved drug target in cancer. The first generation tyrosine kinase inhibitors targeting L858R mutated EGFR are routinely used to treat non-small cell lung cancer (NSCLC). However, the presence of a secondary mutation (T790M) tenders these inhibitors ineffective and thus results in the relapse of the disease. Objective: New reversible inhibitors are required, which act against T790M/L858R (TMLR) double mutants and overcome resistance. Method: In the present study, various Fragment based QSAR (G-QSAR) models along with interaction terms have been studied for amino-pyrimidine derivatives having biological activity against TMLR mutant enzyme. Results: The G-QSAR models developed using partial least squares regression via stepwise forward- backward variable selection technique showed the best results. The model showed a high correlation coefficient (r² = 0.86), cross-validation coefficient (q² = 0.81) and predicted correlation (predicted r² = 0.62), which indicated that the model is robust and predictive. Based on the model, it was revealed that at R1 position increasing saturated carbon (number of –CH atom connected with 3 single bonds i.e. SsssCHcount) and retention index (chi3) is desired for the enhancement of bioactivity. Additionally, at the R2 position, increasing lipophilic character (slogp) and at site R3, the polarizability of compound need to be increased for better inhibitory activity. We further studied the contribution of interactions among significant descriptors in enhancing the activity of the compounds. It revealed that the presence of Sum((R1-SsssCHcount, R2-slogp) and Mult(R1-chi3, R3-polarizabilityAHC) are the most significantly influencing descriptors. We further compared the variation in the most and least active compounds which established that retention of the above properties is essential for imparting significant inhibitory activity to these molecules. Conclusion: The study provides site specific information wherein chemical group variation influences the inhibitory potency of TMLR amino-pyrimidine inhibitors, which can be used for designing new molecules with the desired activity.

Background: A convenient approach to modulation of the inflammation has an influence on the production of inflammatory mediators – icosanoids, generated in arachidonic acid (AA) metabolism. The common therapeutic activity of non-steroidal anti-inflammatory drugs (NSAID), such as aspirin, includes inhibition of two crucial enzymes of AA metabolism - cyclooxygenase- 1 and -2 (COX-1/2), with certain risk for gastrointestinal and renal intolerance. Ever since the enrolment of COX-2, particularly overabundance of its main products prostaglandin E2 (PGE2) and thromboxane A2 (TXA2) in numerous pathological processes was recognized, it became a significant therapeutic target. Objective: The aim of this study was to examine the effects of synthesized organo-fluorine compounds on PGE2 and TXA2 production in the inflammation process. Methods: Trifluoromethyl compounds were synthesized from N-benzyl trifluoromethyl aldimine, commercially available 2-methyl or 2-phenyl α-bromo esters (β-lactams trans-1 and trans-2 and trifluoromethyl β-amino ester, respectively) and methyl 2-isocyanoacetate (2-imidazoline trans-4). The reactions proceeded with high geometric selectivity, furnishing the desired products in good yields. The influence of newly synthesized compounds on PGE2 and TXA2 production in human leukemic U937 macrophages on both enzyme activity and gene expression levels was observed. Results: Among the tested trifluoromethyl compounds, methyl trans-1-benzyl-5-(trifluoromethyl)- 4,5-dihydro-1H-imidazole-4-carboxylate (trans-4) can be distinguished as the most powerful antiinflammatory agent, probably due to its trifluoromethyl-imidazoline moiety. Conclusion: Some further structural modifications in tested compounds and particularly in the synthesis of different trifluoromethyl imidazolines could contribute to the development of new COX-2 inhibitors and potent anti-inflammatory agents.

Background: Norcantharimides are known as norcantharidine derivatives and contain an isoindole skeleton structure. Isoindole derivatives have positive effect on inflammatory pathologies including cancers. Objective: Considering this information, firstly, isoindole derivatives containing different functional groups 4-13 have been synthesized from 2-alkyl/aryl-3a, 4,7,7a-tetrahydro-1H-isoindole-1, 3(2H)-dione. Methods: For the synthesis of all compounds, 2-alkyl/aryl-3a, 4,7,7a-tetrahydro-1H-isoindole- 1,3(2H)-dione was used as the starting compound. The syntheses were based on two main reactions: Ene-reaction of singlet oxygen and epoxidation. Secondly, their anticancer activities were evaluated against HeLa, C6 and A549 cancer cell lines by the BrdU assay. Results: Anticancer activities of synthesized compounds (4-13) and 5-FU (5-Florouracil) against HeLa, C6 and A549 cells were investigated at four concentrations (100, 50, 25 and 5 μM). IC50 values of compounds 4-13 were calculated for all cancer cell lines. The investigated compounds showed anticancer activity against the cancer cell lines depending on doses. Compound 7 containing azide and silyl ether exhibited higher inhibitory activity than the other compounds and 5-FU against A549 cancer cell lines (IC50 =19.41± 0.01 μM). Compounds 9 and 11 were determined to exhibit cell-selective activity against HeLa cancer cell lines. Compound 11 had higher activity than the positive control at 100 μM concentrations against C6 cancer cell lines. Conclusion: According to the results observed, isoindole derivatives 7, 9, and 11 might be good potential anticancer agents for the treatment of cervical and glioma cancer due to their antiproliferative properties, having less cytotoxic effects on healthy cells. In addition, compound 7 could be used in in vivo studies of all three-cancer cell lines (C6, HeLa, and A549).

Background: In order to discover new agents for chemotherapy with improved properties compared to the existing agents and bearing in mind the fact that some Pd complexes possess better antitumor activity and exhibit less kidney toxicity compared to cisplatin, a series of novel square-planar palladium(II) complexes [Pd (L)2] (3a-f) with O,O bidentate ligands [L = ethyl 2- hydroxy-alkyl(aryl)-4-oxo-2-butenoate] were synthesized. Methods: All complexes were characterized by spectral (UV-Vis, IR, NMR, ESI-MS) and X-ray analysis and examined for their cytotoxic effect on human cancer cell lines HeLa and MDA-MB 231 and normal fibroblasts (MRC-5). Fluorescence spectroscopic method was used for investigations of the interactions between CT-DNA or bovine serum albumin (BSA) and complex 3c. Viscosity measurements and molecular docking study were performed to confirm the mode of interactions between DNA and BSA and complex 3c. Results: Complexes that showed the best results, 3c, 3d, and 3e, were placed under further investigations. Selected complexes induced apoptosis and cell cycle arrest in HeLa and MDA-MB 231 cells. Low concentrations of 3c and 3e showed strong to moderate synergism with low concentrations of cisplatin. The interaction of 3d with cisplatin was antagonistic in all used concentrations, but low IC50 value indicates its usefulness as a single cytotoxic agent. It was also noted that the change of viscosity is more pronounced in DNA solution after addition of complex 3c. Conclusion: Obtained results indicate that the novel palladium(II) complexes have the potential to become candidates for treatment in anticancer therapy.

Background: New drugs and strategies to treat tuberculosis (TB) are urgently needed. In this context, thiourea derivatives have a wide range of biological activities, including anti-TB. This fact can be illustrated with the structure of isoxyl, an old anti-TB drug, which has a thiourea as a pharmacophore group. Objective: The aim of this study is to describe the synthesis and the antimycobacterial activity of fifty-nine benzoylthioureas derivatives. Methods: Benzoylthiourea derivatives have been synthesized and evaluated for their activity against Mycobacterium tuberculosis using the MABA assay. After that, a structure-activity relationship study of this series of compounds has been performed. Results and Discussion: Nineteen compounds exhibited antimycobacterial activity between 423.1 and 9.6 μM. In general, we observed that the presence of bromine, chlorine and t-Bu group at the para-position in benzene ring plays an important role in the antitubercular activity of Series A. These substituents were fixed at this position in benzene ring and other groups such as Cl, Br, NO2 and OMe were introduced in the benzoyl ring, leading to the derivatives of Series B. In general, Series B was less cytotoxic than Series A, which indicates that the presence of a substituent at benzoyl ring contributes to an improvement in both antimycobacterial activity and toxicity profiles. Conclusion: Compound 4c could be considered a good prototype to be submitted to further structural modifications in the search for new anti-TB drugs, since it is 1.8 times more active than the first line anti-TB drug ethambutol and 0.65 times less active than isoxyl.

Objective: Due to the incidence of resistance, a series of sulfonamide-derived 1,2,4- triazoles were synthesized and evaluated. Method: The novel sulfonamide-derived 1,2,4-triazoles were prepared starting from commercial acetaniline and chlorosulfonic acid by sulfonylation, aminolysis, N-alkylation and so on. The antimicrobial activity of the synthesized compounds were evaluated in vitro by two-fold serial dilution technique. Results: In vitro antimicrobial evaluation found that 2-chlorobenzyl sulfonamide 1,2,4-triazole 7c exhibited excellent antibacterial activities against MRSA, B. subtilis, B. typhi and E. coli with MIC values of 0.02−0.16 μmol/mL, which were comparable or even better than Chloromycin. The preliminary mechanism suggested that compound 7c could effectively bind with DNA, and also it could bind with human microsomal heme through hydrogen bonds in molecular docking. Computational chemical studies were performed on compound 7c to understand the structural features that are essential for activity. Additionally, compound 7c could generate a small amount of reactive oxygen species (ROS). Conclusion: Compound 7c could serve as a potential clinical antimicrobial candidate.

Background: Topiroxostat is an excellent xanthine oxidase (XO) inhibitor, possessing a specific 3,5-diaryl-1,2,4-triazole framework. Objective: The present work was aimed to investigate the preliminary structure-activity relationship (SAR) of 2-cyanopyridine-4-yl-like fragments of topiroxostat analogues. Methods: A series of 5-benzyl-3-pyridyl-1H-1,2,4-triazole derivatives (1a-j and 2a-j) were designed and synthesized by replacement of the 2-cyanopyridine-4-yl moiety with substituted benzyl groups. XO inhibitory activity in vitro was evaluated. Furthermore, molecular modeling simulations were performed to predict the possible interactions between the synthesized compounds and XO binding pocket. Results: The SARs analysis demonstrated that 3,5-diaryl-1,2,4-triazole framework is not essential; in spite of its lower potency, 5-benzyl-3-pyridyl-1H-1,2,4-triazole is an acceptable scaffold for XO inhibitory activity to some extent. A 3′-nitro and a 4′-sec-butoxy group link to the benzyl moiety will be welcome. Furthermore, the most promising compound, 1h, was identified with an IC50 value of 0.16 μM, and the basis of XO inhibition by 1h was rationalized through the aid of molecular modelling studies. Conclusion: Compound 1h could be a lead compound for further investigation and the present work may provide some insight into the search for more structurally diverse XO inhibitors with topiroxostat as a prototype.

Background: It is assumed that the unfavorable selective toxicity of an antifungal drug Amphotericin B (AmB) can be improved upon chemical modification of the antibiotic molecule. Objective: The aim of this study was verification of the hypothesis that introduction of bulky substituents at the amino sugar moiety of the antibiotic may result in diminishment of mammalian in vitro toxicity of thus prepared AmB derivatives. Methods: Twenty-eight derivatives of AmB were obtained upon chemical modification of the amino group of mycosamine residue. This set comprised 10 N-succinimidyl-, 4 N-benzyl-, 5 Nthioureidyl- and 9 N-aminoacyl derivatives. Parameters characterizing biological in vitro activity of novel compounds were determined. Results: All the novel compounds demonstrated lower than AmB antifungal in vitro activity but most of them exhibited negligible cytotoxicity against human erythrocytes and three mammalian cell lines. In consequence, the selective toxicity of majority of novel antifungals, reflected by the selective toxicity index (STI = EH50/IC50) was improved in comparison with that of AmB, especially in the case of 5 compounds. The novel AmB derivatives with the highest STI, induced substantial potassium efflux from Candida albicans cells at concentrations slightly lower than IC50s but did not trigger potassium release from human erythrocytes at concentrations lower than 100 μg/mL. Conclusion: Some of the novel AmB derivatives can be considered promising antifungal drug candidates.