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anti-HIV Agents: Design and Discovery of New Potent RT Inhibitors
Abstract
This paper reports our work in the field of nonnucleoside RT inhibitors (NNRTIs). On the basis of extensive studies on 1H,3H-thiazolo[3,4-a]benzimidazole derivatives (TBZs) followed by structure-activity relationship (SAR) considerations and molecular modeling, the design and synthesis of a series of 2,3-diaryl-1,3-thiazolidin-4-ones have been performed. Some derivatives proved to be highly effective in inhibiting human immunodeficiency virus type-1 (HIV-1) replication at nanomolar concentrations with minimal toxicity, acting as reverse transcriptase (RT) inhibitors. Computational studies were used in order to probe the binding of our ligands to HIV-1-RT.
... Giving due consideration to the aforesaid, our group and others have explored 2,3-diaryl-1,3-thiazolidin-4-ones for new anti-HIV-1 agents (12)(13)(14)(15)(16)(17)(18)(19). In these explorations, attempts were made to alter the lipophilicity, steric and electronic properties of the compounds to suit to the viral enzyme. ...
... Furthermore, the quantitative structure-activity relationship (QSAR) and docking studies of these analogues suggested the importance of compound's overall hydrophobicity and the presence of hetero atoms on the 2-and 3-aryl moieties of the scaffold for the activity (20). These findings (12)(13)(14)(15)(16)(17)(18)(19)(20) suggested that modification of C-2 and N-3 substitutions of thiazolidin-4-one have scope for further exploration. ...
... Our attempts to separate them were not successful. The compounds were characterized by their spectral analysis through IR, ESI-MS, 1 H-NMR, 13 C-NMR and HRMS. ...
In a focused exploration, thiazolidin-4-ones with different C-2 and N-3 substituent groups were synthesized and evaluated as non-nucleoside reverse transcriptase inhibitors against HIV-1. This has led to new active compounds sporting heteroaryls at both C-2 and N-3 positions prompting to view them in the backdrop of nevirapine. In order to assign the molecular attributes for the activity, the compounds are investigated by docking them into non-nucleoside inhibitor binding pocket of HIV-1 reverse transcriptase (RT). The most active compounds of this series (7d and 7f) shared spatial features with nevirapine with added molecular flexibility. Furthermore, in molecular dynamics simulations carried out for up to 10ns, the compounds 7d and 7f showed consistency in their interactions with non-nucleoside inhibitor binding pocket of HIV-1 RT and suggested Tyr319 and Val106 as potential residues for H-bond interaction with these molecules. These results open new avenues for the exploration of 2,3-diheteroaryl thiazolidin-4-ones for prevention of HIV-1. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
... Investigation of antiviral activity of 4-thiazolidinone derivatives has been carried out mainly in two directions: search for anti HIV agents and search for agents used in hepatitis C treatment. Tested compounds are small molecule inhibitors of validated targets such as HCV NS3 and 5 proteases [39,382], HIV RT [383] etc. Recently, rhodanine derivatives, namely 2-aryl-5-(4-oxo-3phenethyl-2-thioxothiazolidinylidenemethyl)-furans 155 (Scheme 79) were reported to exhibit anti-HIV-1 activity [384] ...
The presented review is an attempt to summarize a huge volume of data on 5-ene-4-thiazolidinones being a widely studied class of small molecules used in modern organic and medicinal chemistry. The manuscript covers approaches to the synthesis of 5-ene-4-thiazolidinone derivatives: modification of the C5 position of the basic core; synthesis of the target compounds in the one-pot or multistage reactions or transformation of other related heterocycles. The most prominent pharmacological profiles of 5-ene derivatives of different 4-thiazolidinone subtypes belonging to hit-, lead-compounds, drug-candidates and drugs as well as the most studied targets have been discussed. Currently target compounds (especially 5-en-rhodanines) are assigned as frequent hitters or pan-assay interference compounds (PAINS) within high-throughput screening campaigns. Nevertheless, the crucial impact of the presence/nature of C5 substituent (namely 5-ene) on the pharmacological effects of 5-ene-4-thiazolidinones was confirmed by the numerous listed findings from the original articles. The main directions for active 5-ene-4-thiazolidinones optimization have been shown: i) complication of the fragment in the C5 position; ii) introduction of the substituents in the N3 position (especially fragments with carboxylic group or its derivatives); iii) annealing in complex heterocyclic systems; iv) combination with other pharmacologically attractive fragments within hybrid pharmacophore approach. Moreover, the utilization of 5-ene-4-thiazolidinones in the synthesis of complex compounds with potent pharmacological application is described. The chemical transformations cover mainly the reactions which involve the exocyclic double bond in C5 position of the main core and correspond to the abovementioned direction of the 5-ene-4-thiazolidinone modification.
... Due to its high efficacy against herpes simplex virus (HSV) and varicella-zoster virus, ACV has been the leading treatment for these pathologies until now (Field, Hodge, 2013). The action mechanism is based on competition with endogenous nucleosides for viral DNA incorporation, which disable DNA chain elongation and, therefore prevent viral replication (Barreca et al., 2003;Lupi, Silva, Pereira, 2000). ...
The evaluation of drug permeation/penetration of semisolid formulations into animal skin can be useful to supplement the pharmaceutical equivalence. This paper describes the in vitro assessment of acyclovir (ACV) into porcine skin from commercial formulations with etermination of drug concentration in different layers of cutaneous tissue to correlate with effective antiviral concentration in order to improve the equivalence decision. Studies were conducted using Franz cells and porcine skin. Selected pharmaceutical creams containing ACV had identical (reference and generic) and different (similar) excipients. A software program was employed for the simulation of antiviral effectiveness in the skin. Regarding ACV skin penetration, the first batch of the generic product showed a significant difference from reference and similar products, while in the second batch all products demonstrated equivalent drug penetration in the skin. Simulation studies suggest that formulations analysed exhibit a pharmacological effect even when in contact with Herpes simplex strains of high IC50 (inhibitory concentration required to reduce viral replication by 50%). According to results, it can be assumed that the in vitro cutaneous permeation/penetration study does not supply sensitivity information regarding small alterations of ACV semisolid formulations due to the variability inherent to the method, although it can be relevant to pharmaceutical equivalence studies in the development of semisolid products. © 2016, Faculdade de Ciencias Farmaceuticas (Biblioteca). All rights reserved.
... [19] 2, 3-disubstituted analogs of Thiazolidinone have proved to be predominantly effective non-nucleoside HIV reverse-transcriptase inhibitors. [20] It was observed that reaction with cyclizing reagents like α-halocarbonyl compounds such as, ClCH 2 COCl, BrCH 2 COCl, BrCH 2 COOEt, and ClCH 2 COCH 2 COOEt in boiling ethanol, with fused sodium acetate, have better biological profiles and a better yield. [21,22] The thiazolidin-4one ring system also occurs in nature as asactithiazic acid, ((-)2-(5-carboxypentyl)thiazolidin-4-one), which is isolated from the Streptomyces strains. ...
Aim: It was aimed to synthesise some novel thiazolidinone derivatives and assess them for antidiabetic activity. Material and Methods: A series of substituted 5-ethylidene-2-(phenylimino) thiazolidin-4-ones were prepared by using phenylthiourea (I) as a starting material. Phenylthiourea on reaction with ethylchloroacetate, in the presence of ethanol and fused sodium acetate, gave 2-(phenylimino) thiazolidin-4-one (II), and 2-(phenylimino) thiazolidin-4-one on further reaction with substituted benzaldehyde gave substituted 5-ethylidene-2- (phenylimino) thiazolidin-4-one (III - XVIII). The synthesized compounds were authenticated on the basis of elemental analysis, IR, 1H NMR, and Mass spectral analysis and some of the compounds were selected on the basis of a literature review, to evaluate them for their antidiabetic activity. Results and Conclusion: All The tested compounds 5-(4-fluorobenzylidene)-2-(phenylimino) thiazolidin-4-on (VII) and 5-(4-Methylbenzylidene)-2-(phenylimino)thiazolidin-4- one (X), 5-(2, 4-dinitrobenzylidene)-2-(phenylamino) thiazolidin-4-one (XVII) were found to be ineffective in lowering the blood glucose level.
... These compounds are also known to target cyclooxygenase (COX) enzymes making thiazolidinone compounds excellent candidates to develop as anti-tumor and anti-inflammatory agents [25,26]. Further, thiazolidone compounds have been shown to inhibit the HIV-1 reverse transcriptase [28][29][30]. Because these compounds showed antiviral activity, we originally investigated thiazolidinone compounds for the ability to inhibit the HCV NS5B polymerase. ...
... For examples, the benzimidazole core structure is found in a variety of commercial drugs such as Atacand, Nexium, Micardis, Protonix, and Vermox ( Figure 1). Recent medicinal chemistry applications of benzimidazole analogs include antibacterial and antifungal agents [1][2][3], anthelmintic agents [4], HIV-1-induced cytopathic inhibitor [5], anti-inflammatory and antiulcer agents [6], cytotoxic and antitumor agents [7,8], DNA binding agents [9], enzyme and OPEN ACCESS receptor agonists or antagonists [10]. Other applications of benzimidazoles include their use as organic ligands [11,12], fluorescent whitening agent dyes [13] and functional materials [14,15]. ...
A straightforward method has been developed for the synthesis of the benzimidazole ring system through a carbon-nitrogen cross-coupling reaction. In the presence of 2.0 equiv. of K(2)CO(3) in water at 100 °C for 30 h, the intramolecular cyclization of N-(2-iodoaryl)benzamidine provides benzimidazole derivatives in moderate to high yields. Remarkably, the procedure occurs exclusively in water and doesn’t require the use of any additional reagent/catalyst, rendering the methodology highly valuable from both environmental and economical points of view.
... So, the plausible pharmacophoric elements for TBZ were: the fused benzene ring, the 2',6'-dihalosubstituted phenyl ring at C-1 and the nitrogen atom of the thiazole nucleus (Fig. 2). It was also evidenced by the extensive structural modifications on TBZ derivatives [15][16][17][18][19][20][21][22][23] (Fig. 3) that specific requirements existed in respect of the determining factors for an optimal anti-HIV potency. ...
Derived from the structure of 1H,3H-thiazolo[3,4-a]benzimidazoles (TBZs), 2,3-diaryl-1,3-thiazolidin-4-one derivatives became a novel class of HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). Under the guidance of continuous structure-activity relationship (SAR) analysis and molecular modeling, various structural modifications were carried out on nearly all the positions of the thiazolidin-4-one nucleus. Some of the derivatives proved to be highly effective against HIV-1 replication at 10-40 nanomolar concentration ranges with minimal cytotoxicities. In this article, the whole development of 2,3-diaryl-1,3-thiazolidin-4-one series from the discoveries to recent advances, their panoramic SAR studies and binding modes based on molecular modeling were reviewed, and also some enlightenments for further investigation were presented.
... Recently, there has been considerable interest in the chemistry and pharmacology of the thiazolidin-4-one containing scaffolds. These compounds display a broad spectrum of biological activities, such as antimycobacterial [7][8][9][10], antifungal [11][12][13], antiviral [14][15][16][17][18], anticancer [13], and anticonvulsant [19] activities. ...
A series of new 2-aryl-4-thiazolidinones (3 and 4) was synthesized from 2-hydroxy-2,2-diphenyl-N'-[(substituted phenyl)methylene]acetohydrazides (2) and mercaptoacetic acid or 2-mercaptopropionic acid. The antimycobacterial activity of these compounds was determined and several leads with 95-99% inhibition at 6.25 microg/mL test concentration were identified. In addition, antitumor activities were measured against several tumor cell lines, and significant growth inhibition was observed for compound 4p. Taken together, 2-aryl-4-thiazolidinones were shown to be promising scaffolds for both antimycobacterial and tumor-targeting compounds.
... The discovery and characterization of new anti-HIV agents with novel structures or mechanism(s) of action and low toxicity to the host remain priority (Barreca et al., 2003). Specific inhibitors of several steps of the viral replicative cycle, including viral attachment and entry, reverse transcription, provirus DNA integration and RNA packaging, have been subjected to preclinical investigation or have already entered clinical trials. ...
The antiviral effect of the CH(2)Cl(2)/MeOH-soluble fraction from the alga Dictyota menstrualis on HIV-1 replication was evaluated in vitro. The antiretroviral activity was attributed to two diterpenes: (6R)-6-hydroxydichotoma-3,14-diene-1,17-dial, named Da-1, and (6R)-6-acetoxi-dichotoma-3,14-diene-1,17-dial, named AcDa-1. Da-1 or AcDa-1 were added to the culture medium of HIV-1-infected PM-1 cells at different times post-infection or during virus adsorption/penetration. The results indicated that the compounds affected an early step of the virus replicative cycle. Virus binding and entry into the host cells were evaluated in the presence of each diterpene, but no inhibitory effect was observed. To evaluate provirus DNA synthesis/integration into the host genome, the viral protease coding sequence was amplified from total cellular DNA. Proviral DNA was not detected in infected cells incubated with the diterpenes. To investigate the effect of the diterpenes on the reverse transcription of the viral genomic RNA, the recombinant HIV-1 reverse transcriptase (RT) was assayed in vitro in the presence of each diterpene. Da-1 and AcDa-1 inhibited the RNA-dependent DNA-polymerase activity of HIV-1 RT in a dose-dependent manner. Taken together, our results demonstrate that both diterpenes inhibit HIV-1 RT and consequently virus replication.
... The discovery and characterization of new anti-HIV agents with novel structures or mechanism(s) of action and low toxicity to the host remain priority (Barreca et al., 2003). Specific inhibitors of several steps of the viral replicative cycle, including viral attachment and entry, reverse transcription, provirus DNA integration and RNA packaging, have been subjected to preclinical investigation or have already entered clinical trials. ...
It has been recently demonstrated that HIV-1 reverse transcriptase is the target of two diterpenes, (6R)-6-hydroxydichotoma-3,14-diene-1,17-dial (compound 1) and (6R)-6-acetoxydichotoma-3,14-diene-1,17-dial (compound 2), that inhibit HIV-1 replication in vitro. In this work, the effects of both diterpenes on the kinetic properties of the recombinant HIV-1 reverse transcriptase (RT) enzyme were evaluated. RNA-dependent DNA-polymerase (RDDP) activity assays demonstrated that both diterpenes behave as non-competitive inhibitors with respect to dTTP and uncompetitive inhibitors with respect to poly(rA)·oligo(dT) template primers. The K i values obtained for compounds 1 and 2 were 10 and 35 μM, respectively. Neither of these diterpenes affected the DNA-dependent DNA-polymerase (DDDP) activity of the HIV-1 RT. The RDDP activities of AMV-RT and MMLV-RT enzymes were also inhibited by compounds 1 and 2. In contrast to the HIV-1 enzyme, the DDDP activities of AMV-RT and MMLV-RT enzymes were significantly reduced by compound 1. Taken together, our results demonstrate that compound 1 is a more effective inhibitor of the viral reverse transcriptases from HIV-1, AMV and MMLV than compound 2. The kinetic behavior analyses of the HIV-1 RT demonstrate that both diterpenes have similar mechanisms of inhibition of RDDP activity.
Abbreviations
Compound 1:(6R)-6-hydroxydichotoma-3,14-diene-1,17-dial
Compound 2:(6R)-6-acetoxydichotoma-3,14-diene-1,17-dial
HIV-1 RT:human immunodeficiency virus type-1 reversetranscriptase
AMV:avian myeloblastosis virus
MMLV:Moloney murine leukemia virus
... Four unsaturated diterpene dialdehydes: dictyodial (10) and 4β-hydroxydictyodial (11), previously isolated from D. dichotoma [19], and (6R)-6-hydroxydichotoma-3,14-diene-1,17-dial (17) and its acetate derivative (6R)-6-acetoxydichotoma-3,14-diene-1,17-dial (18), isolated from D. menstrualis [20] showed inhibitory effects against HIV-RT (reverse transcriptase enzyme) activity. The discovery and characterization of new anti-HIV agents and new sources with either novel structures or mechanism(s) of action and low toxicity to the host remain a priority [21]. The dichotomane diterpenes 17-18 ( Figure 2) inhibited virus replication with EC 50 values of 40 µM (12 µg/mL) and 70 µM (24 µg/mL), respectively. ...
The crude extract of the Brazilian brown alga Dictyota crenulata was analyzed by NMR spectroscopy and HRGC-MS techniques. Seven diterpenes were identified: pachydictyol A, dictyodial, 4beta-hydroxydictyodial A, 4beta-acetoxydictyodial A, isopachydictyol A, dictyol C and dictyotadiol. Xeniane diterpenes have previously been found in D. crenulata from the Pacific Ocean. The results characterize D. crenulata as a species that provides prenylated guaiane (group I) and xeniane diterpenes (group III), thus making it a new source of potential antiviral products.
A series of five -CH3, -NO2, -OCH3 and -Cl substituted 2-hydroxy-2,2-bis(4-phenyl)-N'-[(1E)-(3/4- phenyl)methylene]acetohydrazide (1a-1e) was synthesized by the reaction of 2-hydroxy-2,2-diphenylacetohydrazide with substituted aromatic aldehydes to give intermediate Schiff bases. Structures of the synthesized compounds were characterized using NMR (1D; ¹H, ¹³C/APT and 2D ¹H-¹H COSY, and NOESY), FT-IR, UV, LC-MS/MS spectral data and elemental analysis. The geometry of compounds 1a-1e were determined to be "E" by NOESY. All the tested compounds showed cytotoxic activity on MCF-7 and PC-3 cell line at highest experimental concentration (100 μM). Compounds 1b (18.24 ± 7.62 μM) and 1e (7.62 ± 1.85 μM) have strong anti-proliferative activity on MCF-7 cell line, while compound 1b (45.81 ± 1.10 μM) has the strongest activity on PC-3 cell line.
Twenty novel 2-thioxo-1, 3-thiazolidin-4-one derivatives (5a-5t) were synthesized and evaluated for their antitubercular activity. The structure of the compounds was confirmed by IR, NMR and Mass Spectroscopy methods. In addition, single-crystal X-ray diffraction was performed for compound 5a. All the synthesized compounds were screened for their in-vitro antimycobacterial activity against MTB (H37RV, ATCC No: 27294) by Alamar Blue assay method. Compounds 5r, 5k, 5t displayed most potent in-vitro activity with MICs of 0.05, 0.1, 0.2 μg/ml concentrations respectively which are comparatively potent than the standards. Molecular docking and dynamics simulations were performed to find out the plausible mechanism of the titled compounds.
We have synthesized some novel fluorine containing 5-arylidene derivatives bearing different pharmacophores and heterocyclic systems like quinazolinone along with 4-thiazolidinone, which may act as potential antimicrobial agents. They have been synthesized by the Knoevenagel condensation of N-(2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)-4-(4-oxo-2-p-tolylquinazolin-3(4H)-yl)benzamide with aromatic aldehydes to form N-(5-(aryl)-2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)-4-(4-oxo-2-p-tolylquinazolin-3(4H)-yl)benzamides (6a-t). The products were characterized by IR, H-1, C-13 and F-19 NMR and mass spectral techniques. The synthesized compounds were evaluated for their in vitro antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and fungi (Candida albicans, Aspergillus niger, and Aspergillus clavatus) using serial broth dilution method. Compounds 6b, 6d, 61, 6j, 6k, 6n and 6s were the most noteworthy derivatives identified in the present study because of their remarkable in vitro antimicrobial potency.
This study presents the synthesis, spectral analysis, and antimicrobial evaluation of a new series of 1,3-thiazolidin-4-one derivatives. New compounds were prepared by the reaction of N-substituted carboxylic acid hydrazide derivatives with thioglycolic acid. The structures of the obtained compounds were confirmed by means of 1H NMR and 13C NMR. All the synthesized compounds were screened for their in vitro antibacterial and antifungal activities using the broth microdilution method against a panel of reference strains of 20 microorganisms, including 10 strains of Gram-positive bacteria, 7 strains of Gram-negative bacteria, and fungi belonging to 3 yeasts of Candida spp. Our results indicate that some of the investigated compounds showed good to mild bioactivity, with bacteriostatic or fungistatic effect against reference strains of Gram-positive bacteria, mainly M. luteus and yeast belonging to Candida spp., especially C. albicans.
In continuation of our efforts to develop new derivatives as hepatitis C virus (HCV) NS5B inhibitors, we synthesized novel 5-arylidene-4-thiazolidinones. The novel compounds 29-42, together with their synthetic precursors 22-28, were tested for HCV NS5B inhibitory activity; 12 of these compounds displayed IC50 values between 25.3 and 54.1 µM. Compound 33, an arylidene derivative, was found to be the most active compound in this series with an IC50 value of 25.3 µM. Molecular docking studies were performed on the thumb pocket-II of NS5B to postulate the binding mode for these compounds.
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
As a part of our ongoing research in the development of new antimicrobials, herein, we report the synthesis of ten compounds which combine three bioactive moieties: thiazole, adamantane and 4-thiazolidinone. Evaluation of their antibacterial activity revealed that the newly synthesized compounds exhibited remarkable growth inhibition of a wide spectrum of Gram-positive bacteria, Gram-negative bacteria and fungi. The majority of the compounds displayed greater antibacterial activity than the reference drugs (ampicillin and streptomycin), while the antifungal activity was significantly higher than that of the reference drugs bifonazole and ketoconazole. Additionally, the title compounds were screened for HIV-1 reverse transcriptase inhibitory activity, showing no significant activity. Moreover, docking studies were performed in order to explore possible binding modes at the MurB protein of S. aureus.
This study presents the synthesis, dissociation constants, and pharmacological properties of Schiff base hydrazones. The derivatives were synthesized by the condensation reaction of carboxylic acid hydrazides containing 1,2,4-triazole system with various aldehydes. The new derivatives of 1,3-thiazolidin-4-one were prepared by the cyclization reaction of Schiff base hydrazones with the mercaptoacetic acid in the presence of 1,4-dioxane. The structure of all obtained compounds was confirmed by means of 1H NMR and 13C NMR spectra. The dissociation constants were determined using spectrophotometric method. The effects of four synthesized Schiff base hydrazones 6, 7, 11, and 12 on the central nervous system of mice in behavioral tests were examined.
The reverse transcriptase enzyme has been identified as an attractive target to inhibit the HIV-1 proliferations. Studies about the structure activity relationship on a dataset of thiazolidin-4-ones were performed using the topomer-CoMFA. The obtained topomer-CoMFA model with steric and electrostatic field parameters based on two (labelled R1 and R2) fragments gave a statistically robust model (R
2 = 0.938; Q
2 = 0.719). The predictability of the developed model was assessed on a test set data with r
pred
2
= 0.798. The results of topomer-CoMFA suggested that at R1 position, the large bulky groups at C-2 position with less electronegativity and small bulky groups with large electronegativity at C-6 position are favourable for bioactivity. The topomer-CoMFA results for electrostatic contour maps at R2 position, electron releasing groups at C-4, C-5 and C-6 position along with electronegative atoms at N1 and N3 of pyrimidine, N1 of pyridine or O1 of furan moiety, whereas steric contour maps favour the substitution of small bulky groups at the same position. Finally, the applicability domain of the model was defined on external dataset of thiazolidin-4-ones and the results further supported the reliability and robustness of topomer-CoMFA model, which could be further used for prediction of potential new thiazolidin-4-one analogues.
Six new 1,4-disubstituted thiosemicarbazides were synthesized and their obtaining reactions were optimized in a 2 3 factorial experiment. The structural features of the analyzed compounds were established by spectral means. The tuberculostatic activity against Mycobacterium Tuberculosis has been tested for different concentrations of the studied thiosemicarbazides in DMSO + phosphate buffer in volumetric ratios 1:4. The highest tuberculostatic activity has been registered for compound IV.
Curr HIV Res. 2008 May;6(3):209-17.
The compound 6-chloro-1,4-dihydro-4-oxo-1-(beta-D-ribofuranosyl) quinoline-3-carboxylic acid inhibits HIV-1 replication by targeting the enzyme reverse transcriptase.
Souza TM, Cirne-Santos CC, Rodrigues DQ, Abreu CM, Tanuri A, Ferreira VF, Marques IP, de Souza MC, Fontes CF, Frugulhetti IC, Bou-Habib DC.
Author information
Abstract
We describe in this paper that the chloroxoquinolinic ribonucleoside 6-chloro-1,4-dihydro-4-oxo-1-(beta-D-ribofuranosyl)-quinoline-3-carboxylic acid (compound A) inhibits the HIV-1 replication in human primary cells. We initially observed that compound A inhibited HIV-1 infection in peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner, resulting in an EC(50) of 1.5 +/- 0.5 microM and in a selective index of 1134. Likewise, compound A blocked HIV-1(BA-L) replication in macrophages in a dose-dependent manner, with an EC(50) equal to 4.98 +/- 0.9 microM. The replication of HIV-1 isolates from subtypes C and F was also inhibited by compound A with the same efficiency. Compound A inhibited an early event of the HIV-1 replicative cycle, since it prevented viral DNA synthesis in PBMCs exposed to HIV-1. Kinetic assays demonstrated that compound A inhibits the HIV-1 enzyme reverse transcriptase (RT) in dose-dependent manner, with a K(I) equal to 0.5 +/- 0.04 microM. Using a panel of HIV-1 isolates harboring NNRTI resistance mutations, we found a low degree of cross-resistance between compound A and clinical available NNRTIs. In addition, compound A exhibited additive effects with the RT inhibitors AZT and nevirapine, and synergized with the protease inhibitor atazanavir. Our results encourage continuous studies about the kinetic impact of compound A towards different catalytic forms of RT enzyme, and suggest that our nucleoside represents a promising molecule for future antiretroviral drug design.
(Chemical Equation Presented) Reaction of diacyl thiocarbohydrazides with dimethyl but-2-ynedioate in refluxing ethanol led to 4-oxa-thiazolidine-5- ylidene-acetates in good yields. Reaction of the newly prepared N-(2-(propan-2-ylidene) hydrazine-carbonothioyl)arylhydrazides with dimethyl but-2-ynedioate gave the corresponding (Z)-methyl-2-arylhydrazide-4-oxo-3- (propan-2-ylideneamino)thiazolidine-5-ylidene)-acetates. The mechanism is discussed. Antitumor and antioxidant activities have been also investigated.
One pot synthesis of 2-(substitutedphenyl)-3-[5-(substitutedphenyl)-1,3,4-thiadiazol-2-yl]thiazolidin-4-one was developed by the reaction of 1,3,4-thiadiazole, substituted benzaldehyde and mercaptoacetic acid. These compounds were identified by IR, 1HNMR, elemental analyses and 2-(4-methoxyphenyl)-3-[5-(3-methylphenyl)-1,3,4-thiadiazol-2-yl]thiazolidin-4-one was confirmed by single-crystal X-ray diffraction.
This chapter illustrates the syntheses and reactions of five-membered heterocyclic ring systems containing nitrogen and sulfur. The importance of these pi-rich heterocycles in medicinal chemistry and natural products is also discussed. The chemistry of isothiazoles, reaction of thiazoles with alkylidenecyclopropanes, methods for the synthesis of thiazoles, and use of ebselen, a glutathione peroxidase mimic is also illustrated. The thiazole ring system is found in a variety of medicinally important compounds and many examples have been reported. This chapter also discusses the most widely reported use of the thiazole ring system for the synthesis of non-thiazole containing molecules. Several reports on the isolation and structure determination of various macrocyclic peptides containing the thiazole ring system are also discussed.
A series of 2-aryl-3-(4,5,6-trimethylpyrimidin-2-yl) thiazolidin-4-ones (1a–1c) and their derivatives bearing a lipophilic substituent, like acetoxy group (3a–3c), propionyloxy group (4a–4c), methyl (5d and 5e) at C-5 on thiazolidin-4-one ring were designed, synthesized and evaluated for their HIV-RT inhibitory activity. Using selfcatalyzed
Pummerer reaction, compounds 3a–3c and 4a–4c were obtained in good yield (63.1%–75.2%). Preliminary anti-HIV-RT test of these derivatives indicated that compounds 1a–1c, 4b (propionyloxy group at C-5) showed moderate HIV-RT inhibitory activity and compounds 5d and 5e with methyl at C-5 showed a weak HIVRT inhibitory activity. Structure activity relationship analysis suggested that the substituted
groups on C-5 would be unfavorable to anti-HIV-RT activity and that the steric effect might play a critical role in the anti-HIV
RT activity.
Keywords5-subsituted thiazolidin-4-ones–Pummerer reaction–anti-HIV-RT activity–SARs
2-aryl-3-(naphthalene-1 or 2-yl)-1, 3-thiazolidin-4-ones 4 and 5 were synthesized in 41%–67% yield by using microwave-assisted one-pot protocol. The structures of the new compounds 4l, 4m, 5c, 5e, 5g, 5h, and 5j–5m were confirmed by IR, NMR, MS, and elemental analysis. The antimicrobial activities of the compounds against Pseudomonas syringae pv. lachrymans (Smith et Bryan) Young, Dye & Wilkie, Botrytis cinerea Pers., and Sphaerotheca fusca Blum. were examined. Some of the compounds showed good antifungical activity against Sphaerotheca fusca Blum.
Cytoprotection and cytotoxicity data of anti-HIV 2,3-diaryl-1,3-thiazolidin-4-ones were subjected to QSAR study using Fujita-Ban type analysis and a mixed approach based on Hansch and Fujita-Ban analyses. Apart from appropriate indicator and integer variables encoding different group contributions, different physicochemical variables like hydrophobicity (pi) and steric (molar refractivity) parameters of aryl ring substituents of the compounds were used as predictor variables. Furthermore, Wang-Ford charges of the common atoms of the compounds calculated from molecular electrostatic potential surface of AMI optimized geometries of the compounds and various topological parameters were used as additional descriptors. The variables for the multiple regression analyses were selected based on principal component factor analysis, and generated equations were statistically validated using leave-one-out technique and predicting the activity data of test set compounds. The statistical qualities of the equations for cytoprotection data (explained variance ranging 64.5-80.3%, leave-one-out predicted variance ranging 4.4.3-59.4%) are better than those for cytotoxicity data (explained variance ranging 59.7-60.6%, leave-one-out predicted variance ranging 52.4-54.4%). The analysis explores the structural and physicochemical requirements of the compounds for cytoprotection and cytotoxicity.
Inhibitory activity of 2-(2,6-disubstituted phenyl)-3-(substituted pyrimidin-2-yl)-thiazolidin-4-ones the Human Immunodeficiency Virus-1 Reverse Transcriptase (HIV-1 RT) have been analyzed using Combinatorial Protocol in Multiple Linear Regression (CP-MLR) with several electronic and molecular surface area features of the compounds obtained from Molecular Operating Environment (MOE) software. The study has indicated the role of different charged molecular surface areas in modeling the inhibitory activity of the compounds. The derived models collectively suggested that the compounds should be compact without bulky substitutions on its peripheries for better HIV-1 RT inhibitory activity. It also emphasized the necessity of hydrophobicity and compact structural features for their activity. The scope of the descriptors identified for these analogues have been verified by extending the dataset with different 2-(disubstituted phenyl)-3-(substituted pyridin-2-yl)-thiazolidin-4-ones. The joint analysis of extended dataset highlighted the information content of identified descriptors in modeling the HIV-1 RT inhibitory activity of the compounds.
The asymmetric unit of the title compound, C(20)H(15)N(3)O, contains two independent mol-ecules, each of which is disordered over two sets of sites corresponding to a rotation of approximately 180° of the dihydro-benzimidazoquinazoline moiety, with refined site occupancies of 0.7479 (13) and 0.2521 (12) for both mol-ecules. The pyrimidine rings are in sofa conformations. In one mol-ecule, the hy-droxy-substituted benzene ring forms dihedral angles of 83.9 (3) and 82.4 (4)° for the major and minor components, respectively, with the mean plane of the benzimidazole ring system. The corres-ponding dihedral angles in the other mol-ecule are 88.31 (14) and 85.8 (6)°. In the crystal, mol-ecules are linked via inter-molecular O-H⋯N and N-H.·O hydrogen bonds into chains along [100].
In the title compound, C(16)H(14)BrN(3)O(2)S, the atoms of the 1,3-thia-zolidine group, except for the N and the C atoms attached to the bromo-benzene ring, are disordered over two sets of sites with occupancies of 0.605 (13) and 0.395 (13). The benzene and pyridine rings make a dihedral angle of 86.2 (2)°. In the crystal, mol-ecules are linked by inter-molecular N-H⋯N and C-H⋯O hydrogen bonds, forming a three-dimensional network. Furthermore, there is a π-π stacking inter-action [centroid-centroid distance = 3.758 (2) Å] between the pyridine and benzene rings.
The title compound, C(16)H(14)ClN(3)O(2)S, crystallizes with two mol-ecules in the asymmetric unit. In the 1,3-thia-zolidine rings, the carbonyl O atoms, the S atoms, the methyl groups and the ring carbon attached to the methyl groups are disordered with occupancy ratios of 0.509 (7):0.491 (7) in one mol-ecule and 0.464 (14):0.536 (14) in the other. The crystal structure is stabilized by inter-molecular N-H⋯N, C-H⋯O hydrogen bonds and C-H⋯Cl inter-actions. In addition, there is a π-π stacking inter-action [centroid-centroid distance = 3.794 (3) Å] between the benzene and pyridine rings.
Without any catalyst, 2,3-disubstituted-1,3-thiazolidin-4-one derivatives were synthesized efficiently via the three-component reaction of aldehyde, amine and mercaptoacetic acid in [bmim][PF(6)]. The whole procedure is simple and straightforward and no aqueous work-up is needed. By employing this protocol, a series of novel pyrimidine nucleoside-thiazolidin-4-one hybrids were prepared and their preliminary antiparasitic activities were also studied and reported.
A novel series of 1,4-bis(6-(substituted phenyl)-[1,2,4]-triazolo[3,4-b]-1,3,4-thiadiazoles (5a-b) and 4-bis(substituted phenyl)-4-thiazolidinone derivatives (7a-c) have been synthesized from terephthalic dihydrazide (1) through multistep reaction sequence. 1,4-Bis(5-aryl-1,3,4-oxadiazole-2yl) benzene derivatives (2a-f) and bis-substituted terephthalohydrazide (6a-e) were also synthesized from terephthalic dihydrazide by cyclization with various aromatic acids and aldehydes. Terephthalic dihydrazide (1) was obtained from poly(ethylene terephthalate) waste from reaction with hydrazine hydrate in good yield (86%). All the synthesized compounds were screened for their antibacterial activities against various bacteria and fungi strains. Several of these compounds showed potential antibacterial activity.
This review article presents the fourth part (part D) in the series of stories on antiviral drug discovery. The stories told in part D focus on: (i) the cyclotriazadisulfonamide compounds; (ii) the {5-[(4-bromophenylmethyl]-2-phenyl-5H-imidazo[4,5-c]pyridine} compounds; (iii) (1H,3H-thiazolo[3,4-a]benzimidazole) derivatives; (iv) T-705 (6-fluoro-3-hydroxy-2-pyrazinecarboxamide) and (v) its structurally closely related analogue pyrazine 2-carboxamide (pyrazinamide); (vi) new strategies for the treatment of hemorrhagic fever virus infections, including, as the most imminent, (vii) dengue fever, (viii) the veterinary use of acyclic nucleoside phosphonates; (ix) the potential (off-label) use of cidofovir in the treatment of papillomatosis, particularly RRP (recurrent respiratory papillomatosis); and (x) finally, the prophylactic use of tenofovir to prevent HIV infections.
A series of novel thiazolidin-4-ones bearing a hydrophobic substituent at 5-position on the 4,6-dimethyl-pyrimidine ring at N-3 (5c-i and 6c-i) were designed on the prediction of QSAR studies, synthesized in good yields of 60.1-85.3% by microwave-assisted one-pot protocol with the combination of using dicyclohexylcarbonimide (DCC) as the promotor, and evaluated as HIV-1 reverse transcriptases inhibitors. The results of in vitro HIV-1 RT kit assay showed that some of the new compounds, such as 5c, 6c, 5d, 6d, 5g, 5h and 6i, could effectively inhibit RT activity. Among them, compounds 5c and 6c where ethyl group existed at 5-position on N-3 pyrimidine ring were the best ones with the IC(50) value of 0.26 microM and 0.23 microM, respectively. Structure-activity relationship analysis of these analogues suggested that the overall hydrophobicity and steric factor were important to the anti-HIV RT activity. The mechanism of the intramolecular cycloamidation promoted by DCC was also investigated with the key uncyclized intermediate 13.
Some novel 2-aryl-3-[5-deoxy-1,2-O-isopropylidene-alpha-D-xylofuranose-5-C-yl] thiazolidin-4-ones were synthesized by the three-component condensation of an amino sugar 1, an aromatic aldehyde 2, and mercaptoacetic acid 3 in the presence of DCC and DMAP at room temperature. Two diastereoisomers 4 and 5 were afforded as the main products in totally isolated yields of 25.4-70%. The reaction was carried out with almost no observed stereoselectivity except in the case of 2c, which showed a moderate stereoselectivity. The structures of the new compounds were determined by NMR spectroscopy and mass spectrometry (MS), and the configuration of the newly generated chiral carbon (C-2) in the thiazolidin-4-one ring was tentatively assigned based on the X-ray crystallographic structure of 5d and the comparison of their corresponding NMR signals. The antitumor (human cervical cancer cells) activity and the inhibition against the glycosidases (alpha-glucosidase, beta-glucosidase, alpha-amylase) have been evaluated for the new compounds, some of which exhibited antitumor activity.
Two novel series of 4-thiazolidinone derivatives, namely 2',4'-difluoro-4-hydroxybiphenyl-3-carboxylic acid [2-(5-nitro-2-furyl/substituted phenyl)-4-thiazolidinone-3-yl]amides (5a-g) and 2-(2',4'-difluoro-4-hydroxybiphenyl-3-carbonylhydrazono)-3-alkyl/aryl-4-thiazolidinones (6a-e) together with 5-(2',4'-difluoro-4-hydroxybiphenyl-5-yl)-2-cyclohexylamino-1,3,4-oxadiazole (7a) have been synthesized as title compounds. 1-(2',4'-Difluoro-4-hydroxybiphenyl-3-carbonyl)-4-alkyl/arylthiosemicarbazides (4a-g) were also obtained and used as intermediate to give the title compounds. All synthesized compounds were screened for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv, antiviral and antimicrobial activities against various virus, bacteria and fungi strains.
We describe in this paper that the chloroxoquinolinic ribonucleoside 6-chloro-1,4-dihydro-4-oxo-1-(beta-D-ribofuranosyl)-quinoline-3-carboxylic acid (compound A) inhibits the HIV-1 replication in human primary cells. We initially observed that compound A inhibited HIV-1 infection in peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner, resulting in an EC(50) of 1.5 +/- 0.5 microM and in a selective index of 1134. Likewise, compound A blocked HIV-1(BA-L) replication in macrophages in a dose-dependent manner, with an EC(50) equal to 4.98 +/- 0.9 microM. The replication of HIV-1 isolates from subtypes C and F was also inhibited by compound A with the same efficiency. Compound A inhibited an early event of the HIV-1 replicative cycle, since it prevented viral DNA synthesis in PBMCs exposed to HIV-1. Kinetic assays demonstrated that compound A inhibits the HIV-1 enzyme reverse transcriptase (RT) in dose-dependent manner, with a K(I) equal to 0.5 +/- 0.04 microM. Using a panel of HIV-1 isolates harboring NNRTI resistance mutations, we found a low degree of cross-resistance between compound A and clinical available NNRTIs. In addition, compound A exhibited additive effects with the RT inhibitors AZT and nevirapine, and synergized with the protease inhibitor atazanavir. Our results encourage continuous studies about the kinetic impact of compound A towards different catalytic forms of RT enzyme, and suggest that our nucleoside represents a promising molecule for future antiretroviral drug design.
The structural features, including the absolute configuration, of the enantiomers of 1-(2',6'-difluorophenyl)-1H,3H-thiazolo[3,4-a]benzimidazole (TBZ; NSC 625487), the lead compound of a new class of human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTIs), are described. Diffractometric analysis revealed that TBZ, like other NNRTIs, assumes a butterfly-like conformation in which the phenyl ring at C1 is in an orthogonal orientation relative to the thiazolobenzimidazole system, and the 2',6'-fluorine atoms form two intramolecular hydrogen bonds with H1 and one of the methylene protons at C3, respectively. The stereochemistry in solution, as confirmed by lanthanide shift reagent-assisted H-1 NMR, paralleled the situation present in the solid state. The in the vitro anti-HIV activity of the two enantiomers was also evaluated and the results obtained showed that the R-(+) is more active than the S-(-) isomer in inhibiting HIV-1 replication. Resistance and cross-resistance to other NNRTIs as well as inhibitory effects on HIV-1 reverse transcriptase activity are also reported.
A series of novel 1-aryl-3-methyl-1H,3H-thiazolo[3,4-a]benzimidazoles, TBZ analogues, were synthesized and investigated as anti-human immunodeficiency virus (HIV) agents in order to study the effects of structural modifications on antiviral activity and cytotoxicity. They were proved to inhibit significantly HIV-1 replication in vitro without showing inhibitory activity on HIV-2 or simian immunodeficiency virus. Their potency was influenced by the presence of suitable substituents in the phenyl ring at C-1 as well as by their stereochemical characteristics. In fact, the most active compound of the series was the trans-1-(2,6-difluorophenyl)-3-methyl-1H,3H-thiazolo[3,4- a]benzimidazole, in which the butterfly-like conformation is stabilized by two intramolecular hydrogen bonds between the fluorine atoms and H-1 and H-3. This was made possible by the trans arrangement of C-1 and C-3 substituents, as shown by X-ray and NMR analysis.
Using a known human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitor (NNRTI), 1-(2,6-difluorophenyl)-1H,3H-thiazolo[3,4-a]benzimidazole (TBZ NSC 625487) as the lead structure for drug design, a series of novel 1H,3H-thiazolo[3,4-a]benzimidazole derivatives substituted on the benzene-fused ring was prepared. Their in vitro anti-HIV-1 activity, as well as their inhibitory effects on the viral reverse transcriptase, were evaluated. The structure-activity relationships for these compounds are described and the results suggest that the apolar binding pocket of RT, into which the NNRTIs must fit, can accommodate only groups with a limited size and shape.
Since the Human Immunodeficiency Virus Type 1 (HIV-1) was identified as the etiologic agent of the Acquired Immune Deficiency Syndrome (AIDS), the HIV-1 reverse transcriptase (RT) has been the subject of intensive study. The reverse transcription entails the transition of the single-stranded viral RNA into double-stranded proviral DNA, which is then integrated into the host chromosome. Therefore, the HIV-1 reverse transcriptase plays a pivotal role in the life cycle of the virus and is consequently an interesting target for anti-HIV drug therapy. In the first section, we describe the complex process of reverse transcription and the different activities involved in this process. We then highlight the structure-function relationship of the HIV-1 reverse transcriptase, which is of great importance for a better understanding of resistance development, a major problem in anti-AIDS therapies. Finally, we summarize the mechanisms of HIV resistance toward various RT inhibitors and the implications thereof for the current anti-HIV drug therapies.
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A series of 1H,3H-naphtho[2',3':4,5]imidazo[1,2-c]thiazoles, TBZ analogues, was prepared in order to explore the influence on anti-HIV activity of the spatial requirements of the hydrophobic moiety fused to imidazothiazole system. In spite of a butterfly-like conformation evidenced by X-ray analysis of compound 4g, the results of in vitro screening suggest that the replacement of the benzene fused ring by the naphthyl moiety negatively influences the activity of analogous thiazolobenzimidazole derivatives, some of which are potent non-nucleoside HIV-1 RT inhibitors.
A series of 1-aryl-1H,3H-thiazolo[3,4-a]benzimidazoles were synthesized by one-pot reaction from o-phenylenediamine, 2-mercaptoacetic acid and a variety of aromatic aldehydes. All compounds obtained were evaluated for antiviral activity against human immunodeficiency virus (HIV). Compounds 4g, 4i, 4j, 4l and 4q exhibit reproducible in vitro anti-HIV activity.
A series of 1-aryl-1H,3H-thiazolo[3,4-a]benzimidazoles was synthesized starting from o-phenylenediamine, disubstituted aromatic aldehydes and 2-mercaptoacetic acid. Their antiviral activity against human immunodeficiency virus (HIV) was explored: the 1-(2',6'-dichlorophenyl) (4c), 1-(2',6'-difluorophenyl) (4i), 1-(2'-chloro,6'-fluorophenyl) (4K) and 1-(2'-chloro,5'-nitrophenyl) (4m) derivatives significantly inhibit in vitro the viral cytopathic effect in HIV-infected CEM cells. Compound 4i was selected by NCI's Review Committee for initial preclinical development studies.
The interaction of a probe group with a protein of known structure is computed at sample positions throughout and around the macromolecule, giving an array of energy values. The probes include water, the methyl group, amine nitrogen, carboxy oxygen, and hydroxyl. Contour surfaces at appropriate energy levels are calculated for each probe and displayed by computer graphics together with the protein structure. Contours at negative energy levels delineate contours also enable other regions of attraction between probe and protein and are found at known ligand binding clefts in particular. The contours also enable other regions of attraction to be identified and facilitate the interpretation of protein-ligand energetics. They may, therefore, be of value for drug design.
The development of new nonnucleoside inhibitors of human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) active against the drug-induced mutations in RT continues to be a very important goal of AIDS research. We used a known inhibitor of HIV-1 RT, 1-(2,6-difluorophenyl)-1H,3H-thiazolo[3,4-alpha]benzimidazole (TZB), as the lead structure for drug design with the objective of making more potent inhibitors against both wild-type (WT) and variant RTs. A series of structurally related 1,2-substituted benzimidazoles was synthesized and evaluated for their ability to inhibit in vitro polymerization by HIV-1 WT RT. A structure-activity study was carried out for the series of compounds to determine the optimum groups for substitution of the benzimidazole ring at the N1 and C2 positions. The best inhibitor, 1-(2,6-difluorobenzyl)-2-(2,6-difluorophenyl)-4-methylbenzimida zole (35), has an IC50 = 200 nM against HIV-1 WT RT in an in vitro enzyme assay. Cytoprotection assays utilizing HIV-infected MT-4 cells revealed that 35 had strong antiviral activity (EC50 = 440 nM) against wild-type virus while retaining broad activity against many clinically observed HIV-1 strains resistant to nonnucleoside inhibitors. Overall, the activity of 35 against wild-type and resistant strains with amino acid substitution in RT is 4-fold or greater than that of TZB and is comparable to that of other nonnucleoside inhibitors currently undergoing clinical trials, most of which do not have the capacity to inhibit the variant forms of the enzyme.
Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are promising drugs for the treatment of HIV when used in combination with other anti-HIV drugs such as nucleoside reverse transcriptase (RT) inhibitors and protease inhibitors. The first generation of NNRTIs have, however, suffered from the rapid development of resistance. This review discusses the properties of the FDA-approved NNRTI drugs and focuses on the recent efforts being made to produce second generation inhibitors that circumvent this resistance problem.
A set of TIBO derivatives endowed with reverse transcriptase (RT) inhibitory activity were analyzed by comparative molecular field analysis (CoMFA). Besides conventional steric and electrostatic fields, molecular lipophilicity potential (MLP) was also used as a third field in CoMFA. An informative and statistically significant model (q2 = 0.70, r2 = 0.90, s = 0.46) was obtained by taking into account the three field types together. The key molecular determinants governing the RT inhibition by TIBO congeners were detected at the 3-D level by a careful analysis of the CoMFA isocontour maps. To challenge the predictive ability of the CoMFA model, an external set of thiazolobenzimidazole (TBZ) derivatives were examined. Good predictions, suggesting a similar binding mode for TIBO and TBZ derivatives, emerged. Flexible docking experiments on TBZ, TIBO and other NNIs confirmed common binding characteristics, as found out also by CoMFA, and moreover a good correlation between calculated binding energies and inhibitory potency was found.
Virtually all the compounds that are currently used, or under advanced clinical trial, for the treatment of HIV infections, belong to one of the following classes: (i) nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), (ii) non-nucleoside reverse transcriptase inhibitors (NNRTIs) and (iii) protease inhibitors (PIs). In addition to the reverse transcriptase and protease step, various other events in the HIV replicative cycle are potential targets for chemotherapeutic intervention: (i) viral adsorption, through binding to the viral envelope glycoprotein gp120 (polysulphates, polysulphonates, polyoxometalates, zintevir, negatively charged albumins); (ii) viral entry, through blockade of the viral coreceptors CXCR4 and CCR5 [bicyclams (AMD3100), polyphemusins (T22), TAK-779]; (iii) virus-cell fusion, through binding to the viral glycoprotein gp41 [T-20 (DP-178), siamycins, betulinic acid derivatives]; (iv) viral assembly and disassembly, through NCp7 zinc finger-targeted agents [2,2'-dithiobisbenzamides (DIBAs), azadicarbonamide (ADA)]; (v) proviral DNA integration, through integrase inhibitors such as L-chicoric acid; (vi) viral mRNA transcription, through inhibitors of the transcription (transactivation) process (peptoid CGP64222, fluoroquinolone K-12, Streptomyces product EM2487). Also, in recent years new NRTIs, NNRTIs and PIs have been developed that possess, respectively, improved metabolic characteristics (i.e. phosphoramidate and cyclosaligenyl pronucleotides of d4T), or increased activity against NNRTI-resistant HIV strains, or, in the case of PIs, a different, non-peptidic scaffold. Given the multitude of molecular targets with which anti-HIV agents can interact, one should be cautious in extrapolating from cell-free enzymatic assays to the mode of action of these agents in intact cells. A number of compounds (i.e. zintevir and L-chicoric acid, on the one hand; and CGP64222 on the other hand) have recently been found to interact with virus-cell binding and viral entry in contrast to their proposed modes of action targeted at the integrase and transactivation process, respectively.
Efavirenz is a second-generation non-nucleoside inhibitor of HIV-1 reverse transcriptase (RT) that has recently been approved for use against HIV-1 infection. Compared with first-generation drugs such as nevirapine, efavirenz shows greater resilience to drug resistance mutations within HIV-1 RT. In order to understand the basis for this resilience at the molecular level and to help the design of further-improved anti-AIDS drugs, we have determined crystal structures of efavirenz and nevirapine with wild-type RT and the clinically important K103N mutant.
The relatively compact efavirenz molecule binds, as expected, within the non-nucleoside inhibitor binding pocket of RT. There are significant rearrangements of the drug binding site within the mutant RT compared with the wild-type enzyme. These changes, which lead to the repositioning of the inhibitor, are not seen in the interaction with the first-generation drug nevirapine.
The repositioning of efavirenz within the drug binding pocket of the mutant RT, together with conformational rearrangements in the protein, could represent a general mechanism whereby certain second-generation non-nucleoside inhibitors are able to reduce the effect of drug-resistance mutations on binding potency.
Design, synthesis and anti-HIV activity of a series of 2,3-diaryl-1,3-thiazolidin-4-ones are reported. Some derivatives proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentrations thereby acting as non-nucleoside HIV-1 RT inhibitors (NNRTIs). SAR studies evidenced that the nature of the substituents at the 2 and 3 positions of the thiazolidinone nucleus largely influenced the in vitro anti-HIV activity of this new class of potent antiviral agents.
The synthesis of 1,2-substituted benzimidazoles is reported. These novel derivatives share chemical similarities with 1-aryl-1H,3H-thiazolo[3,4-a]benzimidazoles, a class of HIV-1 NNRTIs studied widely. All compounds prepared were tested in MT-4 cells to explore their potential anti-HIV activity and were found to be less potent than 1-(2,6-difluorophenyl)-1H,3H-thiazolo[3,4-a]benzimidazole (TBZ).
New 1H,3H-oxazolo[3,4-albenzimidazoles (OBZs) were synthesized as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTI) to extend the structure-activity relationships observed for an early series of related 1H,3H-thiazolo[3,4-a]benzimidazole derivatives (TBZs). The new compounds showed inhibitory activity against the replication of various HIV-1 strains, including NNRTI-resistant strains. Testing of a representative OBZ derivative in an HPLC assay on biological fluids, indicated that the sulphur substitution appreciably improved the metabolic stability of the TBZ compound. In addition, molecular modelling studies demonstrated that OBZs, TBZs and other NNRTIs have similar structural properties, that is a butterfly-like conformation, which is a key structural requirement for reverse transcriptase inhibition.
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