Synthesis of alkenyldiarylmethanes (ADAMs) containing benzo[d]isoxazole and oxazolidin-2-one rings, a new series of potent non-nucleoside HIV-1 reverse transcriptase inhibitors

Newly synthesized sulfonamide derivatives explored for DNA binding, enzyme inhibitory, and cytotoxicity activities: a mixed computational and experimental analyses

The current research work reports the synthesis of three 4-((3-arylthiazolo[3,4-d]isoxazol-5-yl)amino)benzene sulfonamide derivatives with a thaizaole(3,4-d)isoxazole-based fused ring heterocyclic system. The synthesized and characterized derivatives, namely, 4-(3-(2-hydroxy-3-methoxyphenyl)thiazolo[3,4-d]soxazole-5-ylamino)benzenesulfonamide (YM-1), 4-(3-(4-chlorophenyl)isoxazolo[3,4-d]thiazol-5-ylamino)benzenesulfonamide (YM-2), and 4-(3-(3-hydroxyphenyl)isoxazolo[3,4-d]thiazol-5-ylamino)benzenesulfonamide (YM-3) were further explored for their binding interactions with DNA and enzymes (urease and carbonic anhydrase). Cytotoxicity of these derivatives for both healthy (HEK-293) and cancerous (MG-U87) cells was determined by MTT analysis. Both experimental (UV-visible, fluorescence, cyclic voltammetry, and viscometry) and theoretical (molecular docking) profiles suggested that these derivatives are good DNA binders. All the derivatives interacted with DNA via mixed intercalative and groove binding interactions. However, the evaluated DNA binding parameters (K b, ΔG, and n) were comparatively greater for YM-1. Docking data (K b and ΔG) for binding of these derivatives with enzymes also supported that YM-1 was a comparatively better inhibitor for carbonic anhydrase. However, experimentally evaluated IC50 (1.90 ± 0.02 μM) and % inhibition (57.93%) were found to be greater for YM-2 against urease enzyme. All the derivatives show dose-dependent cytotoxicity (70-90%) against MG-U87 cancer cells. Conversely, only one concentration of YM-1 (120 μM) showed less toxicity (50.28% with IC50 of 1.154 ± 0.317 μM) than that of the positive control (52.22%) for healthy cells. Overall findings suggested sulfonamide derivative YM-1 is a better candidate for DNA binding, enzyme inhibition as well as anticancer activity.

Synthesis and biological profile of benzoxazolone derivatives

The benzoxazolone nucleus is an ideal scaffold for drug design, owing to its discrete physicochemical profile, bioisosteric preference over pharmacokinetically weaker moieties, weakly acidic behavior, presence of both lipophilic and hydrophilic fragments on a single framework, and a wider choice of chemical modification on the benzene and oxazolone rings. These properties apparently influence the interactions of benzoxazolone-based derivatives with their respective biological targets. Hence, the benzoxazolone ring is implicated in the synthesis and development of pharmaceuticals with a diverse biological profile ranging from anticancer, analgesics, insecticides, anti-inflammatory, and neuroprotective agents. This has further led to the commercialization of several benzoxazolone-based molecules and a few others under clinical trials. Nevertheless, the SAR exploration of benzoxazolone derivatives for the identification of potential "hits" followed by the screening of "leads" provides a plethora of opportunities for further exploration of the pharmacological profile of the benzoxazolone nucleus. In this review, we aim to present the biological profile of different derivatives based on the benzoxazolone framework.

Crystal structure of (R)-5-[(R)-3-(4-chloro-phen-yl)-5-methyl-4,5-di-hydro-isoxazol-5-yl]-2-methyl-cyclo-hex-2-enone

The title compound, C17H18ClNO2, was prepared and isolated as a pure diastereoisomer, using column chromatography followed by a succession of fractional crystallizations. Its exact structure was fully identified via 1H NMR and confirmed by X-ray diffraction. It is built up from a central five-membered di-hydro-isoxazole ring to which a p-chloro-phenyl group and a cyclo-hex-2-enone ring are attached in the 3 and 5 positions. The cyclo-hex-2-one and isoxazoline rings each exhibit an envelope conformation. The crystal packing features C-H⋯O, C-H⋯N and C-H⋯π inter-actions, which generate a three-dimensional network.

The synthetic and therapeutic expedition of isoxazole and its analogs

Isoxazole, constituting an important family of five-membered heterocycles with one oxygen atom and one nitrogen atom at adjacent positions is of immense importance because of its wide spectrum of biological activities and therapeutic potential. It is, therefore, of prime importance that the development of new synthetic strategies and designing of new isoxazole derivatives should be based on the most recent knowledge emerging from the latest research. This review is an endeavor to highlight the progress in the chemistry and biological activity of isoxazole derivatives which could provide a low-height flying bird's eye view of isoxazole derivatives to the medicinal chemists for the development of clinically viable drugs using this information.

Benzisoxazole: a privileged scaffold for medicinal chemistry

The benzisoxazole analogs represent one of the privileged structures in medicinal chemistry and there has been an increasing number of studies on benzisoxazole-containing compounds. The unique benzisoxazole scaffold also exhibits an impressive potential as antimicrobial, anticancer, anti-inflammatory, anti-glycation agents and so on. This review examines the state of the art in medicinal chemistry as it relates to the comprehensive and general summary of the different benzisoxazole analogs, their use as starting building blocks of multifarious architectures on scales sufficient to drive human drug trials. The number of reports describing benzisoxazole-containing highly active compounds leads to the expectation that this scaffold will further emerge as a potential candidate in the field of drug discovery.

Isoxazole ring as a useful scaffold in a search for new therapeutic agents

Due to its relatively easy synthesis, isoxazole ring has been as an object of interest for chemists and pharmacologists from research groups all over the world. Its chemical modifications include both connection of isoxazole with other aromatic, heteroaromatic or non aromatic rings and substitution with different alkyl groups. Thanks to their usually low cytotoxicity, isoxazole derivatives are still popular scaffolds for the development of new agents with variable biological activities, such as antimicrobial, antiviral, anticancer, anti-inflammatory, immunomodulatory, anticonvulsant or anti-diabetic properties. This review discusses the chemical structure of recently developed isoxazole derivatives with regards to their activity and potential therapeutic use.

Seeking potent anti-tubercular agents: Design, synthesis, anti-tubercular activity and docking study of various ((triazoles/indole)-piperazin-1-yl/1,4-diazepan-1-yl)benzo[d]isoxazole derivatives

A series of thirty eight novel 3-(4-((substituted-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl/1,4-diazepan-1-yl)benzo[d]isoxazole and 1-(4-(benzo[d]isoxazol-3-yl)piperazin-1-yl/1,4-diazepan-1-yl)-2-(1H-indol-3-yl)substituted-1-one analogues were synthesised, characterised using various analytical techniques and evaluated for in vitro anti-tubercular activity against Mycobacterium tuberculosis H37Rv strain and two 'wild' strains Spec. 210 and Spec. 192. The titled compounds exhibited minimum inhibitory concentration (MIC) ranging from 6.16 to >200μM. Among the tested compounds, 7i, 7y and 7z exhibited moderate activity (MIC=24.03-29.19μM) and 7j exhibited very good anti-tubercular activity (MIC=6.16μM). Furthermore, 7i, 7j, 7y and 7z were found to be non-toxic against mouse macrophage cell lines when screened for toxicity. All the synthesised compounds were docked to pantothenate synthetase enzyme site to know deferent binding interactions with the receptor.

Design, synthesis and antimycobacterial activity of various 3-(4-(substitutedsulfonyl)piperazin-1-yl)benzo[d]isoxazole derivatives

In this communication, we synthesized a series of twenty four novel 3-(4-(substitutedsulfonyl)piperazin-1-yl)benzo[d]isoxazole analogues, characterized using various spectroscopic techniques and evaluated for their in vitro anti-tubercular activity against Mycobacterium tuberculosis (MTB) H37Rv strain. The titled compounds exhibited Minimum inhibitory concentration (MIC) between 3.125 and >50 μg/mL. Among the tested compounds, 5c, 6a, 6j and 6p exhibited moderate activity (MIC = 12.5 μg/mL), while 5a and 6i exhibited good activity (MIC = 6.25 μg/mL) and 6b (MIC = 3.125 μg/mL) exhibited very good anti-tubercular activity. In addition, the analogues 5a, 5c, 6a, 6b, 6i, 6j and 6p were subjected to toxicity studies against mouse macrophage (RAW 264.7) cell lines to analyse the selectivity profile of the newly synthesized compounds and selectivity index of the most active compound was found to be >130 indicating suitability of the compound for further drug development. Structure of 6b was further substantiated through single crystal XRD.

Synthesis and biological evaluation of some novel urea and thiourea derivatives of isoxazolo[4,5-d]pyridazine and structurally related thiazolo[4,5-d]pyridazine as antimicrobial agents

This study reports the synthesis of some novel isoxazolo[4,5-d]pyridazines and structurally related thiazolo[4,5-d]pyridazines, and their biological evaluation as antimicrobial agents. The proposed compounds were designed to contain pharmacophores such as urea, thiourea, sulfonylurea (thiourea) and some derived functionalities that are believed to contribute to the anticipated biological activities. The results revealed that 25 compounds displayed broad spectrum of antibacterial activity, with greater inhibitory effect on the growth of the tested Gram positive strains compared to Gram negative ones. Moreover, 14 compounds were able to produce appreciable growth inhibitory activity against Candida albicans fungus when compared to Clotrimazole. Most of the tested isoxazolo[4,5-d]pyridazines displayed better antimicrobial profile than their corresponding thiazolo[4,5-d]pyridazine congeners. Four compounds namely, p-(3,7-dimethyl-4-oxo-4H-isoxazolo [4,5-d]pyridazine-5-yl)benzenesulfonylthioureas (11c-d), 3-substituted-2-[p-(3,7-dimethyl-4-oxo-4H-isoxazolo[4,5-d]pyridazine-5-yl)-benzene-sufonylimino]-4-oxothiazolidines (13d) and p-(2,7-dimethyl-4-oxo-4H-thiazolo[4,5-d]pyridazin-5-yl)benzenesulfonylthiourea (24c) were found to be most active antimicrobial members in present study.

5-(3-Methyl-phen-yl)-3-phenyl-1,2-oxazole

In the title compound, C₁₆H₁₃NO, the isoxazole ring makes dihedral angles of 16.64 (7)° with 3-methyl­phenzyl ring and 17.60 (7)° with the unsubstituted phenyl ring.

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

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

The next ten stories on antiviral drug discovery (part E): advents, advances, and adventures

This review article presents the fifth part (part E) in the series of stories on antiviral drug discovery. The ten stories belonging to this fifth part are dealing with (i) aurintricarboxylic acid; (ii) alkenyldiarylmethanes; (iii) human immunodeficiency virus (HIV) integrase inhibitors; (iv) lens epithelium‐derived growth factor as a potential target for HIV proviral DNA integration; (v) the status presens of neuraminidase inhibitors NAIs in the control of influenza virus infections; (vi) the status presens on respiratory syncytial virus inhibitors; (vii) tricyclic (1,N‐2‐ethenoguanine)‐based acyclovir and ganciclovir derivatives; (viii) glycopeptide antibiotics as antivirals targeted at viral entry; (ix) the potential (off‐label) use of cidofovir in the treatment of polyoma (JC and BK) virus infections; and (x) finally, thymidine phosphorylase as a target for both antiviral and anticancer agents. © 2009 Wiley Periodicals, Inc. Med Res Rev, 31, No. 1, 118–160, 2010

1-(3-p-Tolyl-isoxazol-5-yl)cyclo-hexa-nol

The title compound, C₁₆H₁₉NO₂, contains two mol­ecules in the asymmetric unit. Each mol­ecule is composed of three inter­connected rings, two essentially planar rings, viz. the isoxazole and the methyl­benzyl aromatic ring [maximum deviations of 0.0027 (13) and 0.0031 (19) Å from the isoxazole and methylbenzyl ring planes, respectively, in the first molecule, 0.0018 (12) and 0.019 (2) Å in the second molecule], and one cyclo­hexa­nol ring having a chair conformation. Although the two mol­ecules have similar bond distances and angles, they differ in the orientation of the cyclo­hexa­nol ring with respect to the tolyl­isoxazole unit. In the first mol­ecule, the dihedral angle between the isoxazole and methyl­benzyl rings is 22.03 (8)° and between the isoxazole and cyclo­hexa­nol rings is 30.15 (8)°. The corresponding values in the second mol­ecule are 6.13 (10) and 88.44 (8)°, respectively. In the crystal, the molecules are linked by O—H⋯O and O—H⋯N hydrogen bonds, building up a zigzag chain parallel to the a axis.