Anti-HIV agents: design and discovery of new potent RT inhibitors

In-vitro antiviral screening of some thiopyranothiazoles

Thiopyranothiazoles represent a promising class of drug-like molecules with broad pharmacological profiles. Some novel derivatives of isothiochromeno[4a,4-d]thiazole and chromeno[4',3':4,5]thiopyrano[2,3-d]thiazole were synthesized and screened against diverse viruses: coronavirus SARS, Influenza Viruses of type A and type B, Adeno- and Rhinovirus, Dengue Fever Virus, Respiratory Syncytial Virus, Rift Valley Fever Virus, Tacaribe Virus, Venezuelan Equine Encephalitis Virus, as well as Vaccinia and Human Cytomegalovirus. The antiviral activity assays revealed highly active isothiochromeno[4a,4-d]thiazole bearing phenazone fragment towards Influenza Virus type A (H1N1) with the selectivity index (SI) within 150. 5,8-Dihydro-2H-[1,3]thiazolo [5',4':5,6]thiopyrano [2,3-d][1,3]thiazol-2,6(3H)-diones showed moderate antiviral activity against influenza viruses and SARS-CoV. The obtained data indicate thiopyranothiazoles as promising class of fused 4-thiazolidinone derivatives possessing antiviral effects.

Machine intelligence-guided selection of optimized inhibitor for human immunodeficiency virus (HIV) from natural products

The human immunodeficiency virus (HIV) connects to the cluster of differentiation (CD4) and any of the entry co-receptors (CCR5 and CXCR4); followed by unloading the viral genome, reverse transcriptase, and integrase enzymes within the host cell. The co-receptors facilitate the entry of virus and vital enzymes, leading to replication and pre-maturation of viral particles within the host. The protease enzyme transforms the immature viral vesicles into the mature virion. The pivotal role of co-receptors and enzymes in homeostasis and growth makes the crucial target for anti-HIV drug discovery, and the availability of X-ray crystal structures is an asset. Here, we used the machine intelligence-driven framework (A-HIOT) to identify and optimize target-based potential hit molecules for five significant protein targets from the ZINC15 database (natural products dataset). Following validation with dynamic motion behavior analysis and molecular dynamics simulation, the optimized hits were evaluated using in silico ADMET filtration. Furthermore, three molecules were screened, optimized, and validated: ZINC00005328058 for CCR5 and protease, ZINC000254014855 for CXCR4 and integrase, and ZINC000000538471 for reverse transcriptase. In clinical trials, the ZINC000254014855 and ZINC000254014855 were passed in primary screens for vif-HIV-1, and we reported the specific receptor as well as interactions. As a result, the validated molecules may be investigated further in experimental studies targeting specific receptors in order to design and synergize an anti-HIV regimen.

Synthesis, in-Vitro Cytotoxicity and Antimicrobial Evaluations of Some Novel Thiazole Based Heterocycles

Condensation of rhodanine (1) with pyrazol-3(2H)-one derivatives (2a-f) gave 5-substituted-2-thioxo-1,3-thiazolidin-4-one derivatives (3a-f). Reaction of compound (1) with 2-arylmethylidene-malononitrile (4a-d) yielded the unexpected derivatives (5a-d). The latter compounds were subjected to cyclization reactions with malononitrile under different basic conditions, hydroxylamine hydrochloride and/or thiourea to furnish the fused thiazole derivatives (6a-d) and (8-10a-d). Coupling of (1) with diazotized aromatic amines (11a-c) in pyridine afforded the arylhydrazones (12a-c). Fusion of latter compounds with malononitrile afforded the thiazolopyridazine derivatives (13a-c). The structures of the newly synthesized compounds were elucidated via spectral data and elemental analyses. The in-vitro cytotoxic activity of compounds (3a-f) against the cell line MCF-7 was evaluated. Also, the synthesized products were investigated for their antibacterial and antifungal activities against six standard organisms including the G⁺ bacteria, Staphylococcus aureus and Bacillus subtilis, G^- bacteria, Escherichia coli and Proteus vulgaris in addition to fungi, Candida albicans and Aspergillus flavus.

Uses of 2-(Thiophene-2-carbonylcarbamothioylthio)acetic Acid as a Good Synthon for Construction of Some New Thiazole and Annulated Thiazole Derivatives

The reaction of thiophene-2-carbonyl isothiocyanate 2 with thioglycolic acid gave 2-(thiophene-2-carbonylcarbamothioylthio)acetic acid 3. Compound 3 was subjected to some selected reactions with sulphuric acid as well as benzaldehyde, piperonal and isatin under different reaction conditions. The products obtained were new derivatives of thiazole and annulated thiazole derivatives bearing thiophene moiety in some cases. The structures of the new synthesized compounds were confirmed on the basis of their microanalytical and spectral properties. Some compounds were tested for their antimicrobial activity against six selected microorganisms using the standard antibacterial Gentamycin and antifungal Ketoconazole as references.

5-Ene-4-thiazolidinones - An efficient tool in medicinal chemistry

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.

The enantioselective construction of chiral spirooxindole-based 4-thiazolidinone via asymmetric catalytic formal [3+2] annulation using a bifunctional catalyst

A facile and efficient method based on the asymmetric [3+2] annulation of 1,4-dithiane-2,5-diol to ketimines for the construction of chiral spirooxindole-based 4-thiazolidinone was reported.

Synthesis, biological evaluation and molecular modeling studies of new 2,3-diheteroaryl thiazolidin-4-ones as NNRTIs

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. 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 10 ns, 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.

4-Thiazolidinone derivatives as potent antimicrobial agents: microwave-assisted synthesis, biological evaluation and docking studies

A series of ten thiazolidin-4-one derivatives was synthesized and evaluated for their antibacterial, antifungal and HIV-1 reverse transcriptase (RT) inhibitory activity.

2-Heteroarylimino-5-arylidene-4-thiazolidinones as a new class of non-nucleoside inhibitors of HCV NS5B polymerase

Hepatitis C virus (HCV) NS5B polymerase is an important and attractive target for the development of anti-HCV drugs. Here we report on the design, synthesis and evaluation of twenty-four novel allosteric inhibitors bearing the 4-thiazolidinone scaffold as inhibitors of HCV NS5B polymerase. Eleven compounds tested were found to inhibit HCV NS5B with IC₅₀ values ranging between 19.8 and 64.9 μM. Compound 24 was the most active of this series with an IC₅₀ of 5.6 μM. A number of these derivatives further exhibited strong inhibition against HCV 1b and 2a genotypes in cell based antiviral assays. Molecular docking analysis predicted that the thiazolidinone derivatives bind to the NS5B thumb pocket-II (TP-II). Our results suggest that further optimization of the thiazolidinone scaffold may be possible to yield new derivatives with improved enzyme- and cell-based activity.

Aqueous synthesis of 1-H-2-substituted benzimidazoles via transition-metal-free intramolecular amination of aryl iodides

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 K₂CO₃ 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.

2-(5,6-Dihydro-benzimidazo[1,2-c]quinazolin-6-yl)phenol

The asymmetric unit of the title compound, C₂₀H₁₅N₃O, contains two independent mol­ecules, each of which is disordered over two sets of sites corresponding to a rotation of approximately 180° of the dihydro­benzimidazoquinazoline moiety, with refined site occupancies of 0.7479 (13) and 0.2521 (12) for both mol­ecules. The pyrimidine rings are in sofa conformations. In one mol­ecule, the hy­droxy-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 corres­ponding dihedral angles in the other mol­ecule are 88.31 (14) and 85.8 (6)°. In the crystal, mol­ecules are linked via inter­molecular O—H⋯N and N—H.·O hydrogen bonds into chains along [100].

N-[2-(4-Bromo-phen-yl)-5-methyl-4-oxo-1,3-thia-zolidin-3-yl]pyridine-3-carboxamide

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.

N-[2-(4-Chloro-phen-yl)-5-methyl-4-oxo-1,3-thia-zolidin-3-yl]pyridine-3-carboxamide

The title compound, C₁₆H₁₄ClN₃O₂S, crystallizes with two mol­ecules in the asymmetric unit. In the 1,3-thia­zolidine 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 mol­ecule and 0.464 (14):0.536 (14) in the other. The crystal structure is stabilized by inter­molecular N—H⋯N, C—H⋯O hydrogen bonds and C—H⋯Cl inter­actions. In addition, there is a π–π stacking inter­action [centroid–centroid distance = 3.794 (3) Å] between the benzene and pyridine rings.

Yet another ten stories on antiviral drug discovery (part D): paradigms, paradoxes, and paraductions

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.

One pot synthesis of 1,3,4-thiadiazole thiazolidinone derivatives

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, 1H NMR, 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.

Ionic liquid mediated and promoted eco-friendly preparation of thiazolidinone and pyrimidine nucleoside-thiazolidinone hybrids and their antiparasitic activities

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.

Synthesis and biological activity of novel thiazolidin-4-ones with a carbohydrate moiety

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.

Diterpenes from the Brown Alga Dictyota crenulata

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.

Synthesis and biological activity of 4-thiazolidinones, thiosemicarbazides derived from diflunisal hydrazide

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.