Synthesis and SAR of 2-arylbenzoxazoles, benzothiazoles and benzimidazoles as inhibitors of lysophosphatidic acid acyltransferase-β

Direct Synthesis of Benzothiazoles and Benzoxazoles from Carboxylic Acids Utilizing (o-CF3PhO)3P as a Coupling Reagent

A general and efficient method for the direct synthesis of benzothiazoles and benzoxazoles from carboxylic acids with 2-aminobenzenethiols or 2-aminophenols using (o-CF3PhO)3P as a simple coupling reagent has been developed. Diverse benzothiazoles and benzoxazoles were synthesized in moderate to excellent yields. And the gram-scale preparation of benzothiazole and benzoxazole also proceeded smoothly under the mild conditions. Moreover, a plausible reaction mechanism was discussed, with (o-CF3PhO)3P and its hydrolysis product (o-CF3PhO)2P(O)H contributing to the formation of the target products as an amide synthesis coupling agent and a cyclization reaction promoter, respectively.

Benzothiazole derivatives in the design of antitumor agents

Benzothiazoles are a class of heterocycles with multiple applications as anticancer, antibiotic, antiviral, and anti-inflammatory agents. Benzothiazole is a privileged scaffold in drug discovery programs for modulating a variety of biological functions. This review focuses on the design and synthesis of new benzothiazole derivatives targeting hypoxic tumors. Cancer is a major health problem, being among the leading causes of death. Tumor-hypoxic areas promote proliferation, malignancy, and resistance to drug treatment, leading to the dysregulation of key signaling pathways that involve drug targets such as vascular endothelial growth factor, epidermal growth factor receptor, hepatocyte growth factor receptor, dual-specificity protein kinase, cyclin-dependent protein kinases, casein kinase 2, Rho-related coil formation protein kinase, tunica interna endothelial cell kinase, cyclooxygenase-2, adenosine kinase, lysophosphatidic acid acyltransferases, stearoyl-CoA desaturase, peroxisome proliferator-activated receptors, thioredoxin, heat shock proteins, and carbonic anhydrase IX/XII. In turn, they regulate angiogenesis, proliferation, differentiation, and cell survival, controlling the cell cycle, inflammation, the immune system, and metabolic alterations. A wide diversity of benzothiazoles were reported over the last years to interfere with various proteins involved in tumorigenesis and, more specifically, in hypoxic tumors. Many hypoxic targets are overexpressed as a result of the hypoxia-inducible factor activation cascade and may not be present in normal tissues, providing a potential strategy for selectively targeting hypoxic cancers.

Phospholipid Acyltransferases: Characterization and Involvement of the Enzymes in Metabolic and Cancer Diseases

This review delves into the enzymatic processes governing the initial stages of glycerophospholipid (phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine) and triacylglycerol synthesis. The key enzymes under scrutiny include GPAT and AGPAT. Additionally, as most AGPATs exhibit LPLAT activity, enzymes participating in the Lands cycle with similar functions are also covered. The review begins by discussing the properties of these enzymes, emphasizing their specificity in enzymatic reactions, notably the incorporation of polyunsaturated fatty acids (PUFAs) such as arachidonic acid and docosahexaenoic acid (DHA) into phospholipids. The paper sheds light on the intricate involvement of these enzymes in various diseases, including obesity, insulin resistance, and cancer. To underscore the relevance of these enzymes in cancer processes, a bioinformatics analysis was conducted. The expression levels of the described enzymes were correlated with the overall survival of patients across 33 different types of cancer using the GEPIA portal. This review further explores the potential therapeutic implications of inhibiting these enzymes in the treatment of metabolic diseases and cancer. By elucidating the intricate enzymatic pathways involved in lipid synthesis and their impact on various pathological conditions, this paper contributes to a comprehensive understanding of these processes and their potential as therapeutic targets.

Efficient and Eco-Friendly Perspectives for C-H Arylation of Benzothiazole Utilizing Pd Nanoparticle-Decorated Chitosan

In this contribution, an eco-friendly, sustainable, and efficient palladium nanoparticle-decorated chitosan (Pd@Chitosan) catalyst was synthesized by a simple impregnation method. The synthesized material was utilized as a heterogeneous catalyst for the C-H arylation of benzothiazole under ultrasonic irradiation. The Pd@Chitosan catalyst efficiently catalyzed the conversion of aryl iodides and bromides to 1-(4-(benzothiazol-2-yl)phenyl)ethan-1-one selectively. A single product of 83–93% yield was obtained in N,N-dimethylformamide solvent at 80 °C for 2.5h. This study reveals that Pd@Chitosan is an efficient catalyst, which catalyzes the C-H arylation with good reaction yields. The activity of the Pd@Chitosan is due to the presence of highly dispersed Pd(0) nanoparticles on the surface of the chitosan and Pd2+; a tentative mechanism was proposed based on the XPS results of the fresh catalyst and spent catalyst.

Discovery and computational studies of 2-phenyl-benzoxazole acetamide derivatives as promising P2Y14R antagonists with anti-gout potential

The P2Y₁₄ nucleotide receptor, a subtype of P2Y receptors, is implicated in many human inflammatory diseases. Based on the identification of favorable residues of two screening hits in the almost symmetrical P2Y₁₄ binding domain, we describe the structural optimization of previously identified virtual screening hits 6 and 7 that result in the development of P2Y₁₄R antagonists with a novel 2-phenyl-benzoxazole acetamide chemical scaffold. Notably, compound 52 showed potent P2Y₁₄R antagonistic activity (IC₅₀ = 2 nM), and a stronger inhibitory effect on MSU-induced inflammatory in vitro, better than a previously described P2Y₁₄R antagonist PPTN. In vivo evaluation demonstrated that compound 52 also had satisfactory inhibitory activity on the inflammatory response of gout flares in mice. Moreover, P2Y₁₄R antagonist 52 decreased paw swelling and inflammatory cell infiltration through cAMP/NLRP3/GSDMD signaling pathways in MSU-induced acute gouty arthritis mice. The discussions on the binding mechanism that employ MM/GBSA free energy calculations/decompositions also provide some useful clues for further structural designing of compound 52. Taken together, 2-phenyl-benzoxazole acetamide derivative 52 with potent P2Y₁₄R antagonistic activity and in vivo potency could be a promising strategy for gout therapy and deserves further optimization.

Visible-light-promoted photocatalyst-free alkylation and acylation of benzothiazoles

Herein we report a protocol for the visible-light-mediated alkylation/acylation reaction of benzothiazoles. Alkyl/acyl substituted Hantzsch esters are easily prepared and rationally used as radical precursors. In the presence of BF3·Et2O and Na2S2O8, various benzothiazole derivatives were readily obtained in good yields. Our user-friendly protocol can proceed by simple irradiation with blue LEDs (λ = 465 nm) and without the assistance of external photocatalysts. The reaction is also characterized by mild conditions and scalability, thus offering an alternative and efficient tool for the synthesis of 2-functionalized benzothiazoles.

Optimized Synthesis of New N-Mustards Based on 2-Mercaptobenzoxazole Derivatives with Antitumor Activity

New di-(β-chloroethyl)-amides of some acids derived from 2-mercaptobenzoxazole were prepared by reaction of the corresponding pivalic mixed anhydrides with di-(β-chloroethyl)-amine. A study regarding the optimization of the chemical reactions was made for the case of di-(β-chloroethyl)-amines. The quantum chemical analysis by Spartan'14 was made in order to establish the most stable configuration of the ground electronic states for the obtained chemical structures and some physico-chemical parameters of N-mustards reported in this paper. Mercaptobenzoxazoles substituted in the side chain with the cytotoxic group show antitumor activity and they inhibit Ehrlich Ascites in an appreciable proportion compared to the drug I.O.B.-82, as our studies evidenced.

Fast and high-efficiency synthesis of 2-substituted benzothiazoles via combining enzyme catalysis and photoredox catalysis in one-pot

An efficient and green method, combining enzymatic and visible-light catalysis for synthesis of the widely applicable 2-substituted benzothiazoles, has been developed. This method features a relay catalysis protocol consisting of biocatalytic promiscuity and visible-light-induced subsequent oxidization of 2-phenyl benzothiazolines. The whole reaction process is very high-efficiency, achieving 99% yield in just 10 min, under an air atmosphere, nearly 100% atomic utilization, and the 2-substituted benzothiazole products were obtained in good to excellent yields with a wide range of substrates. This reaction is the other example of combining the non-natural catalytic activity of hydrolases with visible-light catalysis for organic synthesis and the catalytic system does not require additional oxidants or metals, which is good for the environment.

Skin Damages-Structure Activity Relationship of Benzimidazole Derivatives Bearing a 5-Membered Ring System

In the search for scaffolds for multifunctional compounds we investigated the structure activity relationship of a class of benzimidazole derivatives bearing 5-membered ring. The newly synthesized and the already known compounds were divided into three classes that present different substituent at 5 position of the benzimidazole ring (-H, -COOH or –SO₃H) and different heterocycle at position 2 (thiophene, furan or pyrrole). All the derivatives were synthesized and tested to determine their photoprotective profile against UV rays, in vitro antioxidant capacity against different radicals (DPPH and FRAP test), antifungal inhibitory activity (dermatophytes and Candida albicans), antiviral and antiproliferative activity. A Structure-Activity Relationship study indicated compound 10, bearing a pyrrole heterocycle on the benzimidazole ring, as the best multifunctional derivative of the series and as potential candidate for the development of drugs especially in case of melanoma.

Synthesis, Structure Revision, and Cytotoxicity of Nocarbenzoxazole G

The total synthesis of nocarbenzoxazoles F (1) and G (2), originally obtained from the marine-derived halophilic bacterial strain Nocardiopsis lucentensis DSM 44048, was achieved via a simple and versatile route involving microwave-assisted construction of a benzoxazole skeleton, followed by carbon-carbon bond formation with the corresponding aryl bromides. Unfortunately, the ¹H and ¹³C NMR spectra of natural nocarbenzoxazole G did not agree with those of the synthesized compound. In particular, the spectra of the isolated and synthesized compounds showed considerable differences in the signals from the protons and carbons in the aryl group. The revised structure was validated by the total synthesis of the actual nocarbenzoxazole G (8c) molecule, which is a regioisomer of the compound that was reported earlier as nocarbenzoxazole G. The synthesized derivatives showed specific cytotoxicity to the human cervical carcinoma cell line, HeLa, but did not have any remarkable effect on the other cell lines.

An efficient synthesis of benzothiazole using tetrabromomethane as a halogen bond donor catalyst

A CBr₄ catalyzed simple, mild, and efficient protocol has been developed for the synthesis of 2-substituted benzothiazole from 2-aminothiophenols and N-methylthioamides under solvent free conditions.

Oxalic/malonic acids as carbon building blocks for benzazole, quinazoline and quinazolinone synthesis

Oxalic/malonic acids as CH/C₂H₃ carbon building blocks for the synthesis of 2-substituted and un-substituted benzazoles, quinazolines and quinazolinones.

Benzophenone based fluorophore for selective detection of Sn2+ ion: Experimental and theoretical study

Synthesis of novel benzophenone-based chemosensor is presented for the selective sensing of Sn²⁺ ion. Screening of competitive metal ions was performed by competitive experiments. The specific cation recognition ability of chemosensor towards Sn²⁺ was investigated by experimental (UV-visible, fluorescence spectroscopy, ¹H NMR, ¹³C NMR, FTIR and HRMS) methods and further supported by Density Functional Theory study. The stoichiometric binding ratio and binding constant (K_a) for complex is found to be 1:1 and 1.50×10⁴, respectively. The detection limit of Sn²⁺ towards chemosensor was found to be 0.3898ppb. Specific selectivity and superiority of chemosensor over another recently reported chemosensor is presented.

Iron-catalyzed synthesis of benzoxazoles by oxidative coupling/cyclization of phenol derivatives with benzoyl aldehyde oximes

An iron-catalyzed oxidative coupling/cyclization reaction for the synthesis of benzoxazoles at room temperature is reported.

Design, Synthesis, and Pharmacological Evaluation of 2-(2,5-Dimethyl-5,6,7,8-tetrahydroquinolin-8-yl)-N-aryl Propanamides as Novel Smoothened (Smo) Antagonists

A series of novel Smo antagonists were developed either by directly incorporating the basic skeleton of the natural product artemisinin or by first breaking artemisinin into structurally simpler and stable intermediates and then reconstructing into diversified heterocyclic derivatives, equipped with a Smo-targeting bullet. 2-(2,5-Dimethyl-5,6,7,8-tetrahydroquinolin-8-yl)-N-arylpropanamide 65 was identified as the most potent, with an IC₅₀ value of 9.53 nM against the Hh signaling pathway. Complementary mechanism studies confirmed that 65 inhibits Hh signaling pathway by targeting Smo and shares the same binding site as that of the tool drug cyclopamine. Meanwhile, 65 has a good plasma exposure and an acceptable oral bioavailability. Dose-dependent antiproliferative effects were observed in ptch+/-;p53-/- medulloblastoma cells, and significant tumor growth inhibitions were achieved for 65 in the ptch+/-;p53-/- medulloblastoma allograft model.

Chemical modulation of glycerolipid signaling and metabolic pathways

Thirty years ago, glycerolipids captured the attention of biochemical researchers as novel cellular signaling entities. We now recognize that these biomolecules occupy signaling nodes critical to a number of physiological and pathological processes. Thus, glycerolipid-metabolizing enzymes present attractive targets for new therapies. A number of fields-ranging from neuroscience and cancer to diabetes and obesity-have elucidated the signaling properties of glycerolipids. The biochemical literature teems with newly emerging small molecule inhibitors capable of manipulating glycerolipid metabolism and signaling. This ever-expanding pool of chemical modulators appears daunting to those interested in exploiting glycerolipid-signaling pathways in their model system of choice. This review distills the current body of literature surrounding glycerolipid metabolism into a more approachable format, facilitating the application of small molecule inhibitors to novel systems. This article is part of a Special Issue entitled Tools to study lipid functions.

Fe-promoted oxidative cyclization of α-benzoylthioformanilides for the synthesis of 2-benzoylbenzothiazoles

This protocol has the advantages of short reaction times, moderate to good yields, convenient manipulation, and high selectivities.

(2E)-2-(1,3-Benzo-thia-zol-2-yl)-3-(di-methyl-amino)-prop-2-ene-nitrile

The mol-ecular conformation of title compound, C12H11N3S, is almost planar [maximum deviation = 0.063 (2) Å]; an intra-molecular C-H⋯N hydrogen bond is noted. In the crystal, mol-ecules inter-act with each other via π-π stacking inter-actions between thia-zole rings [centroid-centroid distance = 3.7475 (9) Å] and methyl-H⋯π(C6) inter-actions, forming columns along the a axis.

Ab initio HF, DFT and experimental (FT-IR) investigation of vibrational spectroscopy of 3-(2-(4-isopropylpiperazin-1-yl)-2-oxoethyl)-6-(4-methoxybenzoyl)benzo[d]thiazol-2(3H)-one

FT-IR spectra was recorded for 3-(2-(4-isopropylpiperazin-1-yl)-2-oxoethyl)-6-(4-methoxybenzoyl)benzo[d]thiazol-2(3H)-one molecule (abbreviated as IOMBT) sample in solid state. Conformational analysis of IOMBT was performed to determine the most stable conformer. Potential energy curves of IOMBT were obtained performing a relaxed scan of D1-7 dihedral angels at B3LYP/6-311++G(d,p) level of theory. Geometrical parameters of these structures were optimized by using the same method. The molecular geometry of IOMBT was reoptimized at DFT(B3LYP) and HF methods using 6-311++G(d,p), 6-311+G(d), 6-311G(d,p), 6-311G(d) and 6-31++G(d,p) basis sets for the lowest energy conformer. The vibrational frequencies, IR intensities were calculated at DFT(B3LYP) and HF methods. The thermodynamic parameters (such as zero-point vibrational energy, EHOMO, ELUMO, thermal corrections to energy, enthalpy and Gibbs free energy, and entropy) have also been computed. The LUMO-HOMO energy gap of IOMBT shows that the energy gap reflects the chemical reactivity and the level of conductivity of the molecule.

Recent advances on structural modifications of benzothiazoles and their conjugate systems as potential chemotherapeutics

INTRODUCTION

Benzothiazole scaffold comprises a bicyclic ring system and is known to exhibit a wide range of biological properties including antimicrobial and anticancer activities. Benzothiazole derivatives have long been therapeutically used for the treatment of various diseases. However, in recent years, 2-arylbenzothiazoles have emerged as an important pharmacophore in the development of antitumor agents. The promising biological profile and synthetic accessibility have been attractive in the design and development of new benzothiazoles and their conjugate systems as potential chemotherapeutics.

AREAS COVERED

This review mainly focuses on the structural modifications of benzothiazole scaffold, development of various series of benzothiazoles and their conjugates as new antitumor agents. Furthermore, heterocyclic derivatives bearing benzothiazole moiety and their in vitro as well as in vivo screening, structure-activity relationships (SAR), mechanism, pharmacokinetics, clinical use and their future therapeutic applications are discussed here.

EXPERT OPINION

A large number of benzothiazole derivatives discussed here possess potent anticancer activity and can be further developed as drug candidates. Benzothiazole conjugates could also display synergistic effect and still there is a need to use the drug combinations permitting lower dose and development of new generation of drugs. Despite encouraging results that have been observed for their response to tumor in clinical studies, full characterization of their toxicity is further required for their clinical usage as safe drugs for the treatment of cancer. We believe that this review gives a better understanding and scope for future drug design and development of benzothiazole-based compounds to implicate their use in cancer chemotherapy.