Five-membered Heterocyclic Ring Research Articles

Crystal structure of a three-coordinate lithium complex with monodentate phenyloxazoline and hexamethyldisilylamide ligands

The reaction of lithium hexamethyldisilylamide, [Li{N(Si(CH3)3)2}] (LiHMDS), with 4,4-dimethyl-2-phenyl-2-oxazoline (Phox, C11H13NO) in hexane produced colourless crystals of bis(4,4-dimethyl-2-phenyl-2-oxazoline-κN)(hexamethyldisilylamido-κN)lithium, [Li(C6H18NSi2)(C11H13NO)2] or [Li{N(Si(CH3)3)2}(Phox)2] in high yield (89%). Despite the 1:1 proportion of the starting materials in the reaction mixture, the product formed with a 1:2 amide:oxazoline ratio. In the unit cell of the C2/c space group, the neutral molecules lie on twofold rotation axes coinciding with the Li—N(amide) bonds. The lithium(I) centre adopts a trigonal–planar coordination geometry with three nitrogen donor atoms, one from the HMDS anion and two from the oxazolines. All ligands are monodentate. In the phenyloxazoline units, the dihedral angle defined by the five-membered heterocyclic rings is 35.81 (5)°, while the phenyl substituents are approximately face-to-face, separated by 3.908 (5) Å. In the amide, the methyl groups assume a nearly eclipsed arrangement to minimize steric repulsion with the analogous substituents on the oxazoline rings. The non-covalent interactions in the solid-state structure of [Li{N(Si(CH3)3)2}(Phox)2] were assessed by Hirshfeld surface analysis and fingerprint plots. This new compound is attractive for catalysis due to its unique structural features.

Rational Design of Fluorophores Using MO Theory: Our Journey from BODIPYs to BOIMPYs

This short review demonstrates how MO-theoretical considerations can support the tailor-made design of new dye scaffolds, specifically the recently introduced BOIMPY class of fluorophores. Starting with historical and structural foundations, the influence of canonical streptocyanines on the electronic features of diarylmethanes and rhodamines is examined and the BODIPY scaffold is introduced as the primary structural inspiration for our work. The attachment of five-membered ring heterocycles at the meso position of the BODIPY core enables a relaxation into a co-planar and twofold chelating triarylmethane system. After introduction of two electron-withdrawing BF2 units efficient rigidity is achieved since hindered rotation prevents non-radiative dissipation of energy via vibrational relaxation. Hence, a lowered LUMO level allows the combination of a large red shift with high quantum efficiencies. The synthetic approach to these systems is straightforward and analogous to BODIPY syntheses starting from benzimidazole or tetrazole carbaldehydes. Cyclic voltammetric measurements prove that BOIMPYs are able to easily accept two electrons and might act as efficient photoredox catalysts.

[Fe(NCMe)6](BF4)2 is a bifunctional catalyst for styrene aziridination by nitrene transfer and heterocycle expansion by subsequent dipolar insertion

The solvated iron(II) salt [Fe(NCMe)6](BF4)2 (Me = methyl) is shown to be a bifunctional catalyst with respect to aziridination of styrene. The salt serves as an active catalyst for nitrene transfer from PhINTs to styrene to form 2-phenyl-N-tosylaziridine (Ph = phenyl; Ts = tosyl, –S{O}2–p-C6H4Me). The iron(II) salt also acts as a Lewis acid in non-coordinating CH2Cl2 solution, to catalyze heterolytic CN bond cleavage of the aziridine and insertion of dipolarophiles. The 1,3-zwitterionic intermediate is presumably supported by interaction of the metal dication with the anion, and by resonance stabilization of the carbocation. Nucleophilic dipolarophiles then insert to give a five-membered heterocyclic ring. The result is a two-step cycloaddition, formally [2 + 1 + 2], that is typically regiospecific, but not stereospecific. This reaction mechanism was confirmed by conducting a series of one-step, [3 + 2] additions of unsaturated molecules into pre-formed 2-phenyl-N-tosylaziridine, also catalyzed by [Fe(NCMe)6](BF4)2. Relevant substrates include styrenes, carbonyl compounds and alkynes. These yield five-membered heterocylic rings, including pyrrolidines, oxazolidines and dihydropyrroles, respectively. The reaction scope appears limited only by the barrier to formation of the dipolar intermediate, and by the nucleophilicity of the captured dipolarophile. The bifunctionality of an inexpensive, earth-abundant and non-toxic catalyst suggests a general strategy for one-pot construction of heterocyclic rings, as demonstrated specifically for pyrrolidine ring formation.

Continuous isomerisation of 2,5-dimethylfuran to 2,4-dimethylfuran over Ga-silicate.

2,4-dimethylfuran has a rare disubstitution pattern in the five-membered heterocyclic furan ring that is highly interesting chemically but challenging to access synthetically. We present a heterogeneously catalysed route to synthesise 2,4-dimethylfuran from commonly available 2,5-dimethylfuran using a zeolite packed-bed flow reactor. As supported by DFT calculations, the reaction occurs inside the zeolite channels, where the acid sites catalyse proton transfer followed by migration of a methyl group. The zeotype Ga-silicate (MFI type) appears superior to an aluminium-containing ZSM-5 by demonstrating higher selectivities and slower catalyst deactivation. This work provides new opportunities for the continuous valorisation of bio-feedstock molecules in the perspective of the emerging biorefinery era.

Glutathione Peroxidase-like Antioxidant Activity of 1,3-Benzoselenazoles: Synthesis and In Silico Molecular Docking Studies as Pancreatic Lipase Inhibitors.

The synthesis of 1,3-benzoselenazoles was achieved by the reaction of corresponding bis[3-amino-N-(p-tolyl)benzamide-2-yl] diselenide, bis[3-amino-N-(4-methoxyphenyl)benzamide-2-yl] diselenide, and bis[3-amino-N-(4-(dimethylamino)phenyl) benzamide-2-yl] diselenide with aryl aldehydes. The 1,3-benzoselenazoles continued to exist as planar molecules due to the presence of secondary Se···O interactions as revealed by the single-crystal X-ray analysis. The presence of secondary Se···O interactions in 1,3-benzoselenazoles was confirmed using natural bond orbital (NBO) and atoms in molecules (AIM) calculations. Nucleus-independent chemical shift (NICS) values suggested the presence of aromatic character in a five-membered benzoselenazole heterocyclic ring. The glutathione peroxidase (GPx)-like antioxidant activity of all 1,3-benzoselenazoles was assessed using a thiophenol assay, exhibiting greater antioxidant activity than Ph2Se2 used as a reference. The most active catalyst carrying a strong electron-donating group (-NMe2) at the ortho-position to the benzoselenazole ring was further investigated at different concentrations of thiophenol, H2O2, and 1,3-benzoselenazoles as catalyst for determining their catalytic parameters. Moreover, the potential applications of all 1,3-benzoselenazoles against pancreatic lipase (PL) have been identified using in silico interactions between the active sites of the 1LPB protein as evaluated using a molecular docking study.

Green synthesis, antibacterial and antifungal evaluation of new thiazolidine-2,4-dione derivatives: molecular dynamic simulation, POM study and identification of antitumor pharmacophore sites

In this study, a series of thiazolidine-2,4-dione derivatives 3a–i were synthesized and evaluated for antibacterial activity against Gram-positive and Gram-negative strains of Bacillus licheniformis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Newly prepared thiazolidine (TZD) derivatives were further screened separately for in vitro antifungal activity against cultures of fungal species, namely, Aspergillus niger, Alternaria brassicicola, Chaetomium murorum, Fusarium oxysporum, Lycopodium sp. and Penicillium notatum. The electron-donating substituents (–OH and –OCH3) and electron-withdrawing substituents (–Cl and –NO2) on the attached arylidene moieties of five-membered heterocyclic ring enhanced the broad spectrum of antimicrobial and antifungal activities. The molecular docking study has revealed that compound 3h strongly interacts with the catalytic residues of the active site of the β-carbonic anhydrase (P. aeruginosa) and has the best docking score. In silico pharmacokinetics studies showed the drug-likeness and non-toxic nature of the synthesized compounds, which indicates the combined antibacterial, antiviral and antitumor pharmacophore sites of the targeted drug. This work demonstrates that potential TZD derivatives bind to different types of bacterial and fungal pathogens for circumventing their activities and opens avenues for the development of newer drug candidates that can target bacterial and fungal pathogens. Communicated by Ramaswamy H. Sarma

1,3-thiazole Derivatives: A Scaffold with Considerable Potential in the Treatment of Neurodegenerative Diseases.

1,3-thiazoles, which contain nitrogen and a sulfur atom is an unsaturated five-membered heterocyclic ring, have achieved a unique significant place in drug design and development because of their versatile structure and a variety of pharmacological activities, viz. anticancer, antiviral, antimicrobial, anticonvulsant, antioxidant, antidiabetic, etc. They have inspired researchers to design novel thiazole with different biological activities. The presence of the thiazole moiety has resulted in a large number of clinically useful drugs with a wide range of activities, such as Ritonavir (antiviral), Sulfathiazole (antimicrobial antibiotic), Abafungin, Ravuconazole (antifungal), Meloxicam (NSAID), etc., that further verify this statement. The prevalence of neurodegenerative diseases like Alzheimer's, Parkinson's, and Huntington's is increasing at a rapid pace but existing treatments mainly provide symptomatic relief and are associated with undesired effects. Consequently, designing novel compounds with more effectiveness and reduced toxicity are required. 1,3-thiazole derivatives have emerged as excellent candidate in this regard and have an important role for the treatment of neurodegenerative diseases. In the current review, we have gathered all the appropriate literature which demonstrate the remarkable role of 1,3-thiazole and its derivatives in these diseases that may help design new compounds with more desired characteristics. The literature was assessed through worldwide scientific databases like GOOGLE, SCOPUS, and PUBMED using different keywords, and only relevant information published in English was evaluated.

Evaluation of genotoxicity of (4-fluorophenyl) thiazolidin-4-one in CHO-K1 cells

4-thiazolidinones are five-membered heterocyclic ring compounds with diverse pharmacological impacts. In a previous study, we reported a series of newly synthesized derivatives of 4-thiazolidinones with different functional groups, which exhibited anticancer activity against ovarian (SKOV3) and cervical (HeLa) cancer cell lines. Among these derivatives, (4-fluorophenyl) thiazolidin-4-one (4-TH) demonstrated potent cytotoxic activity against SKOV3, with an IC50 value of 12.3 μM. However, it was also found to be extremely toxic to normal cells (CHO-K1) with an IC50 of 7.5 μM. Before considering its use in cancer research, it is crucial to gain a comprehensive understanding of its potential genotoxic effects on normal cells. In this study, we aimed to assess the in vitro cytogenetic toxicity of 4-TH using normal Chinese hamster ovary cells (CHO-K1). Referring to the IC50 of 4-TH, we selected three sub-lethal concentrations (2, 5, and 7.5 μM) and treated CHO-K1 cells for 24 h (one cell cycle duration) to estimate its dose-dependent induction of chromosome aberrations, and examine the effect of 4-TH on cell division, micronucleus induction potential and cell cycle arrest properties following standard protocols. The results showed that 4-TH was highly toxic to normal cells, as all three sublethal concentrations caused a statistically significant increase in the number of chromosomal aberrations (P < 0.001), formation of micronuclei (P < 0.01), and changes in the rate of cell division (mitotic index) (P < 0.05) compared to control. In addition, there was a significant increase in the number of cells in the G1 phase, indicating that all concentrations of 4-TH tested induced apoptosis. The evaluation of the cytotoxic, clastogenic, and aneugenic properties of 4-TH, a potent cytotoxic agent, will undoubtedly provide critical information for determining its safety and potential as an anticancer drug.

Attosecond charge migration in heterocyclic five-membered rings

Attosecond charge migration in heterocyclic five-membered rings

Theoretical Investigation of the E/Z Photoisomerization Pathway in 1-(2-Pyrrolyl)-2-(2-thienyl)ethylene.

Molecular-level understanding of photochemistry in simple vinylene-linked systems such as ethylene and stilbene has been a major area of research. However, the effect of replacing the two benzene rings by five-membered heterocyclic rings, thiophene and pyrrole, is yet to be reported. In the present theoretical study, our aim is to illustrate photoinduced processes in a vinylene-linked thiophene-pyrrole system. Computational studies are carried out at the RI-MP2/RI-ADC(2)/cc-pVTZ level to explore different isomerization pathways. Minimum-energy conical intersection (MECI) structures are categorized into two types: closed-ring and twisted-pyramidalized structures. Relaxation through the former MECIs is accessible only from the cis isomers. However, the latter MECIs are inaccessible due to high energy barriers along the linear interpolation in internal coordinate paths.

Pregnenolone sulfate analogues differentially modulate GABAA receptor closed/desensitised states.

GABAA receptors are regulated by numerous classes of allosteric modulators. However, regulation of receptor macroscopic desensitisation remains largely unexplored and may offer new therapeutic opportunities. Here, we report the emerging potential for modulating desensitisation with analogues of the endogenous inhibitory neurosteroid, pregnenolone sulfate. New pregnenolone sulfate analogues were synthesised incorporating various heterocyclic substitutions located at the C-21 position on ring D. The pharmacological profiles of these compounds were assessed using electrophysiology and recombinant GABAA receptors together with mutagenesis, molecular dynamics simulations, structural modelling and kinetic simulations. All seven analogues retained a negative allosteric modulatory capability whilst exhibiting diverse potencies. Interestingly, we observed differential effects on GABA current decay by compounds incorporating either a six- (compound 5) or five-membered heterocyclic ring (compound 6) on C-21, which was independent of their potencies as inhibitors. We propose that differences in molecular charges, and the targeted binding of analogues to specific states of the GABAA receptor, are the most likely cause of the distinctive functional profiles. Our findings reveal that heterocyclic addition to inhibitory neurosteroids not only affected their potency and macroscopic efficacy but also affected innate receptor mechanisms that underlie desensitisation. Acute modulation of macroscopic desensitisation will determine the degree and duration of GABA inhibition, which are vital for the integration of neural circuit activity. Discovery of this form of modulation could present an opportunity for next-generation GABAA receptor drug design and development.

A Review on Synthetic Strategies for Useful Oxadiazole Derivatives in Psychological Disorders

Abstract: Oxadiazole is a five-membered aromatic heterocyclic ring having two nitrogen and one oxygen atom. Various isomeric forms have been reported for oxadiazole, such as 1,3,4-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, etc. Currently, a considerable population worldwide is facing several mental problems due to a competitive lifestyle. The present status of available medicines do not promise complete cure without any adverse effects. Therefore, these disorders are continuously challenging the researchers to come up with new molecules with superior efficacy and minimum side effects. All the isomeric forms of oxadiazole have numerous potential in treating various mental problems such as Parkinsonism, Alzheimer’s, schizophrenia, and epileptic disorders. In this review article, we summarize several recently reported synthetic strategies for preparing different oxadiazole and its derivatives which were found effective in psychological disorders. The researchers will be able to obtain the necessary information (synthesis strategies) through this article for their future research on new molecules containing the oxadiazole moiety. Furthermore, this review article will help the researchers in the fight against mental disorders and highlights possible molecules for the treatment of mentally challenged people.

Theoretical Investigation of Electron Impact Scattering on Imidazole.

This study presents the results of electron scattering calculations on a biologically important molecule, imidazole, using the UK molecular R-matrix method. The R-matrix calculations are performed using SE, SEP, and CC models, and the resonance detected in the present SEP model is found to be in better agreement with available experimental data than previous theoretical data. The study also reports an inelastic scattering cross section, which comprises dissociative electron attachment (DEA), excitation, and ionization cross section, for the first time. The total scattering cross sections are also reported for the first time. We confirm the presence of the two well-known π* shape resonances predicted earlier experimentally. Due to the scarcity of total scattering cross section (TCS) data for imidazole, we have compared the TCS of imidazole with its isoelectronic target isoxazole and drawn important conclusions. A comparison among the resonances of imidazole with those of isoxazole helps us to conclude that electron attachment to π* molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds. The comprehensive electron scattering studies presented in this work are expected to provide a deeper understanding of electron-induced biochemical processes and fill gaps in the available data. Furthermore, this study is anticipated to inspire further investigations on imidazole and other five-membered heterocyclic ring molecules, which have significant applications in medicine.

Five-Membered Heterocyclic Sulfonamides as Carbonic Anhydrase Inhibitors

The development of heterocyclic derivatives has progressed considerably over the past decades, and many new carbonic anhydrase inhibitors (CAIs) fall into this field. In particular, five-membered heterocyclic sulfonamides have been generally shown to be more effective inhibitors compared to six-membered rings ones. Despite the importance of oxygen and nitrogen five-membered heterocyclic aromatic rings in medicinal chemistry, the installation of sulfonamide moiety on such heterocycles has not received much attention. On the other hand, 1,3,4-thiadiazole/thiadiazoline ring-bearing sulfonamides are the scaffolds which have been widely used in a variety of pharmaceutically important CAIs such as acetazolamide, metazolamide and their many derivatives obtained by using the tail approach. Here, we reviewed the field focusing on the diverse biological activities of these CAIs, such as antiglaucoma, antiepileptic, antitumor and antiinfective properties. This review highlights developments involving five-membered heterocyclic sulfonamides over the last years, with a focus on their pharmacological/clinical applications.

Review on Chemistry of Oxazole derivatives: Current to Future Therapeutic Prospective

ABSTRACT Oxazole and its derivatives play a very essential role in the area of medicinal chemistry. Oxazole nucleus is heterocyclic five-membered ring that seemed to be investigated in the advancement of novel compounds which shows favorable biological activities. In the modern medicinal chemistry scaffold of oxazole has been intermittently satisfied as a functional lead molecule. Prominently, enormous oxazole candidates or drugs are developed for the treatment of disease which increases its developmental values as medicinal agents. The five-membered aromatic ring of oxazole has atoms of nitrogen and oxygen. Through diverse non-covalent bonds, these rings quickly engage physiologically with many enzymes and receptors, resulting in a variety of biological actions. This review presents a logical attempt toward the researches and advancement of chemistry and oxazole derivatives’ biological action. The important information presented in this manuscript will work as impetus for new views in the pursuit for rational design of more biologically active and minimum toxic derivatives of oxazoles as medicinal agents.

In silico molecular docking against C-KIT Tyrosine Kinase and ADME studies of 3-Ethyl-2-(2,3,4-trifluoro-phenylimino)-thiazolidin-4-one derivatives

Thiazolidin-4-one derivatives have been hailed as “wonder nucleus” due to their profound biological activities. A number of derivatives with variable functional groups attached to the five-membered heterocyclic ring which have been synthesized and further subjected to molecular docking studies, against C-KIT Tyrosine kinase target protein (1T46). The interactions, binding and affinity variations due to differences in functional groups have been studied using ChemDraw Ultra 7.0, RCSB – Protein Data Bank, BIOVIA Discovery Studio Visualizer 2021, MGL AutoDock Tools, AutoDock Vina and Vina Split software. The docking studies showed good interaction of the synthesized molecules with the 1T46 target protein. The ADME studies of these molecules have also been studied to identify which of the synthesized molecules have the potential to cross the Human Intestinal lining (HIA), as well as the BBB barrier. Out of the 18 molecules studied, 12 of them showed good potential to be absorbed by the intestine out of which only one molecule was able to show potential to cross the BBB barrier. There were 4 molecules that could not cross both the barrier. These studies could reveal which functionalities present attached to the thiazolidin-4-one could assist in human intestinal absorption and the crossing of the BBB barrier.

An Overview of 1,2,3-triazole-Containing Hybrids and Their Potential Anticholinesterase Activities.

Acetylcholine (ACh) neurotransmitter of the cholinergic system in the brain is involved in learning, memory, stress responses, and cognitive functioning. It is hydrolyzed into choline and acetic acid by two key cholinesterase enzymes, viz., acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). A loss or degeneration of cholinergic neurons that leads to a reduction in ACh levels is considered a significant contributing factor in the development of neurodegenerative diseases (NDs) such as Alzheimer's disease (AD). Numerous studies have shown that cholinesterase inhibitors can raise the level of ACh and, therefore, enhance people's quality of life, and, at the very least, it can temporarily lessen the symptoms of NDs. 1,2,3-triazole, a five-membered heterocyclic ring, is a privileged moiety, that is, a central scaffold, and is capable of interacting with a variety of receptors and enzymes to exhibit a broad range of important biological activities. Recently, it has been clubbed with other pharmacophoric fragments/molecules in hope of obtaining potent and selective AChE and/or BuChE inhibitors. The present updated review succinctly summarizes the different synthetic strategies used to synthesize the 1,2,3-triazole moiety. It also highlights the anticholinesterase potential of various 1,2,3-triazole di/trihybrids reported in the past seven years (2015-2022), including a rationale for hybridization and with an emphasis on their structural features for the development and optimization of cholinesterase inhibitors to treat NDs.

Intermolecular Interactions of Edaravone in Aqueous Solutions of Ethaline and Glyceline Inferred from Experiments and Quantum Chemistry Computations.

Edaravone, acting as a cerebral protective agent, is administered to treat acute brain infarction. Its poor solubility is addressed here by means of optimizing the composition of the aqueous choline chloride (ChCl)-based eutectic solvents prepared with ethylene glycol (EG) or glycerol (GL) in the three different designed solvents compositions. The slurry method was used for spectroscopic solubility determination in temperatures between 298.15 K and 313.15 K. Measurements confirmed that ethaline (ETA = ChCl:EG = 1:2) and glyceline (GLE = ChCl:GL = 1:2) are very effective solvents for edaravone. The solubility at 298.15 K in the optimal compositions was found to be equal xE = 0.158 (cE = 302.96 mg/mL) and xE = 0.105 (cE = 191.06 mg/mL) for glyceline and ethaline, respectively. In addition, it was documented that wetting of neat eutectic mixtures increases edaravone solubility which is a fortunate circumstance not only from the perspective of a solubility advantage but also addresses high hygroscopicity of eutectic mixtures. The aqueous mixture with 0.6 mole fraction of the optimal composition yielded solubility values at 298.15 K equal to xE = 0.193 (cE = 459.69 mg/mL) and xE = 0.145 (cE = 344.22 mg/mL) for glyceline and ethaline, respectively. Since GLE is a pharmaceutically acceptable solvent, it is possible to consider this as a potential new liquid form of this drug with a tunable dosage. In fact, the recommended amount of edaravone administered to patients can be easily achieved using the studied systems. The observed high solubility is interpreted in terms of intermolecular interactions computed using the Conductor-like Screening Model for Real Solvents (COSMO-RS) approach and corrected for accounting of electron correlation, zero-point vibrational energy and basis set superposition errors. Extensive conformational search allowed for identifying the most probable contacts, the thermodynamic and geometric features of which were collected and discussed. It was documented that edaravone can form stable dimers stabilized via stacking interactions between five-membered heterocyclic rings. In addition, edaravone can act as a hydrogen bond acceptor with all components of the studied systems with the highest affinities to ion pairs of ETA and GLE. Finally, the linear regression model was formulated, which can accurately estimate edaravone solubility utilizing molecular descriptors obtained from COSMO-RS computations. This enables the screening of new eutectic solvents for finding greener replacers of designed solvents. The theoretical analysis of tautomeric equilibria confirmed that keto-isomer edaravone is predominant in the bulk liquid phase of all considered deep eutectic solvents (DES).

Synthesis, Biological Activity and Applications of 1,2,5-Oxadiazol: A Brief Review

Oxadiazoles are heterocyclic compounds that belong azole class which contain two nitrogen atoms and one oxygen, forming a five-membered heterocyclic ring. Four isomers of oxadiazoles are described in the literature. Among these, 1,2,4-oxadiazole, 1,2,5-oxadiazole, and 1,3,4-oxadiazole have several applications biological. Compounds of this type have been used in the treatment of various diseases in both humans and animals.Among the immense class of heterocycle compounds with important biological activities already identified, the 1,2,5-oxadiazoles have stood out for the wide variety of applications in medicinal chemistry, in material, and agricultural chemistry. In this work, the main synthesis methods and advances for obtaining 1,2,5-oxadiazoles and their derivatives reported in the literature over the years are reviewed, as well as the applications of these compounds in several branches of chemistry and their biological activities discovered until the moment.

Anticancer Potential of Compounds Bearing Thiazolidin-4-one Scaffold: Comprehensive Review

Thiazolidin-4-ones is a versatile and privileged nucleus comprising of a five five-membered heterocyclic ring system possessing sulphur heteroatom and a cyclic amide bond. Extensive research and review studies mainly published in the last decade explored the diverse types of biological activities of this nucleus with potential therapeutic applications. Various silent features like drug likeness behaviour, suitability for diversity-oriented synthesis, and its sensitivity toward the redox tumour m