Recent advances in synthesis, metal complexes and biological evaluation of 2-aryl, 2-pyridyl and 2-pyrimidylbenzothiazoles as potential chemotherapeutics

In the pursuit of novel therapeutic agents: synthesis, anticancer evaluation, and physicochemical insights of novel pyrimidine-based 2-aminobenzothiazole derivatives

Cancer remains a worldwide healthcare undertaking, demanding continual innovation in anticancer drug development due to frequent drug resistance and adverse effects associated with existing therapies. The benzothiazole compounds, particularly 2-aminobenzothiazole derivatives, have attracted interest for their versatility in generating novel anticancer agents. This study explores the synthesis, and anticancer evaluation of new pyrimidine-based 2-aminobenzothiazole derivatives. A range of synthetic methods have been developed based on the reaction of 2-benzothaizolyl guanidine with various reagents such as α,β-unsaturated carbonyl, 2-cyano-three-(dimethylamino)-N-acrylamide, β-diketones, β-keto esters, and S,S ketene dithioacetals. Human tumour cell lines such as HepG2, HCT116, and MCF7 were used in in vitro cytotoxicity studies, and the results showed that several of the synthesized compounds were more potent than the standard drug, 5-fluorouracil, in terms of cell viability% with low IC50. Furthermore, the computed drug likeness and ADMET properties of the most potent synthesized compounds suggest their potential as promising candidates for further development, with favorable bioavailability and pharmacokinetic profiles.

Synthesis and Biological Evaluation of Benzothiazolyl-pyridine Hybrids as New Antiviral Agents against H5N1 Bird Flu and SARS-COV-2 Viruses

A novel series of benzothiazolyl-pyridine hybrids 8a-h and 14a-e were produced from the reaction of enamine derivative 4 with each of the arylcyanoacetamides 5a-h and cyanoacetohydrazides 9a-e. The new products were characterized by spectral techniques (IR, 1H NMR, 13C NMR, and MS). Biological evaluation of 8a-h and 14a-e in vitro against H5N1 and SARS-COV-2 viruses showed that several compounds had significant activity. Compounds 8f-h, which contain fluorine atoms, have better activity against H5N1 and anti-SARS-CoV-2 viruses than the other compounds included in this study. Compound 8h has a trifluoromethyl group at position-3 of the phenyl ring and exhibits a high activity against H5N1 virus with 93 and 60% inhibition at concentrations of 0.5 and 0.25 μmol/μL, respectively, among the tested compounds, and it also showed anti-SARS-CoV-2 virus with a half-maximum inhibition rate of 3.669 μM, among the remaining compounds. The mechanism of action of 8f-h, which is expected to be repurposed against COVID-19, was investigated. The results showed that the compounds have virucidal effects at different stages of the three mechanisms of action. Furthermore, compounds 8f-h were found to possess CoV-3CL protease inhibitory activities with IC50 values of 544.6, 868.2, and 240.6 μg/mL, respectively, compared to IC50 = 129.8 μg/mL of the standard drug lopinavir. Interestingly, compounds 8f-h also showed high inhibitory activity against the H5N1 virus as well as the SARS-CoV-2 virus. Moreover, compounds 8f-h fit admirably into the active site of the SARS-CoV-2 main protease (PDB ID: 6LU7) using the molecular docking Moe software 2015.10.

Crystal structure of 2-{[5-(methyl-sulfan-yl)-4-phenyl-4H-1,2,4-triazol-3-yl]meth-yl}benzo[d]thia-zole

In the structure of the title compound, C17H14N4O2, the triazole ring exhibits inter-planar angles of 63.86 (2) and 76.96 (2)° with the phenyl and benzo-thia-zole planes, respectively. The C-C-C angle at the methyl-ene group is rather wide at 114.28 (4)°. The packing involves three borderline C-H⋯N contacts, two of which combine to form layers parallel to ac, and a pairing of the triazole rings across an inversion centre [inter-planar distance of 3.1852 (2) Å].

Novel Fluorescent Benzothiazolyl-Coumarin Hybrids as Anti-SARS-COVID-2 Agents Supported by Molecular Docking Studies: Design, Synthesis, X-ray Crystal Structures, DFT, and TD-DFT/PCM Calculations

This study revealed the design and preparation of new 3-(benzo[d]thiazol-2-yl)-2H-chromen-2-one derivatives 9a-h. The structures of the synthesized products were elucidated by their spectroscopic data and X-ray crystallography for compounds 9a and 9d. The prepared new compounds were measured for their fluorescence, and a good result indicated that the emission efficiency was decreased by increasing the electron-withdrawing groups from the unsubstituted compound 9a to the highly substituted derivative 9h (2 Br heavy atoms). On the other hand, the B3LYP/6-311G** theoretical level of theory was used to optimize the quantum mechanical calculations of the geometrical characteristics and energy of the novel compounds 9a-h under study. The electronic transition was investigated using the TD-DFT/PCM B3LYP approach, which uses time-dependent density functional calculations. Moreover, the compounds exhibited nonlinear optical properties (NLO) and a small HOMO-LUMO energy gap, which makes them easy to polarize. Furthermore, the acquired infrared spectra were compared with the expected harmonic vibrations of the substances 9a-h. On the other hand, binding energy analyses of compounds 9a-h with human corona virus nucleocapsid protein Nl63 (PDB ID: 5epw) were predicted using molecular docking and virtual screening tools. The results showed a promising binding and how these potent compounds were inhibiting the COVID-19 virus. Compound 9h was the most active anti-COVID-19 agent among all the synthesized benzothiazolyl-coumarin derivatives, as it forms five bonds. The presence of the two bromine atoms in its structure was responsible for the potent activity.

Design, Synthesis and Biological Activities of (Thio)Urea Benzothiazole Derivatives

(Thio)ureas ((T)Us) and benzothiazoles (BTs) each have demonstrated to have a great variety of biological activities. When these groups come together, the 2-(thio)ureabenzothizoles [(T)UBTs] are formed, improving the physicochemical as well as the biological properties, making these compounds very interesting in medicinal chemistry. Frentizole, bentaluron and methabenzthiazuron are examples of UBTs used for treatment of rheumatoid arthritis and as wood preservatives and herbicides in winter corn crops, respectively. With this antecedent, we recently reported a bibliographic review about the synthesis of this class of compounds, from the reaction of substituted 2-aminobenzothiazoles (ABTs) with iso(thio)cyanates, (thio)phosgenes, (thio)carbamoyl chlorides, 1,1'-(thio)carbonyldiimidazoles, and carbon disulfide. Herein, we prepared a bibliographic review about those features of design, chemical synthesis, and biological activities relating to (T)UBTs as potential therapeutic agents. This review is about synthetic methodologies generated from 1968 to the present day, highlighting the focus to transform (T)UBTs to compounds containing a range substituents, as illustrated with 37 schemes and 11 figures and concluded with 148 references. In this topic, the scientists dedicated to medicinal chemistry and pharmaceutical industry will find useful information for the design and synthesis of this interesting group of compounds with the aim of repurposing these compounds.

Crystal structure of 3-(benzo[d]thia-zol-2-yl)-6-methyl-2H-chromen-2-one

The mol-ecule of the title compound, C₁₇H₁₁NO₂S, is almost planar, with an inter-planar angle of 3.01 (3)° between the benzo-thia-zole and chromene ring systems. A short intra-molecular S⋯O=C contact of 2.727 (2) Å is observed. The crystal packing involves a layer structure parallel to (211), containing dimeric inversion-symmetric units connected by a 'weak' C-H⋯O=C hydrogen bond.

Synthesis and Biological Importance of 2-(thio)ureabenzothiazoles

The (thio)urea and benzothiazole (BT) derivatives have been shown to have a broad spectrum of biological activities. These groups, when bonded, result in the 2-(thio)ureabenzothizoles (TBT and UBT), which could favor the physicochemical and biological properties. UBTs and TBTs are compounds of great importance in medicinal chemistry. For instance, Frentizole is a UBT derivative used for the treatment of rheumatoid arthritis and systemic lupus erythematosus. The UBTs Bentaluron and Bethabenthiazuron are commercial fungicides used as wood preservatives and herbicides in winter corn crops. On these bases, we prepared this bibliography review, which covers chemical aspects of UBTs and TBTs as potential therapeutic agents as well as their studies on the mechanisms of a variety of pharmacological activities. This work covers synthetic methodologies from 1935 to nowadays, highlighting the most recent approaches to afford UBTs and TBTs with a variety of substituents as illustrated in 42 schemes and 13 figures and concluded with 187 references. In addition, this interesting review is designed on chemical reactions of 2-aminobenzothiazoles (2ABTs) with (thio)phosgenes, iso(thio)cyanates, 1,1′-(thio)carbonyldiimidazoles [(T)CDI]s, (thio)carbamoyl chlorides, and carbon disulfide. This topic will provide information of utility for medicinal chemists dedicated to the design and synthesis of this class of compounds to be tested with respect to their biological activities and be proposed as new pharmacophores.

4-Amino-5-(4-bromobenzoyl)-3-(benzo[d]thiazol-2-yl)-2-[(2′,3′,4′,6′-tetra-O-acetyl-β-D-galactopyranosyl)sulfanyl]thiophene

In the title compound, C32H29BrN2O10S3, the benzothiazole and thiophene ring systems subtend an interplanar angle of 7.43 (12)°. The NH2 group forms intramolecular hydrogen bonds to Nthiazole and Ocarbonyl. The Sgalactose—Cthiophene bond is short [1.759 (2) Å]. The molecules are connected to form ribbons parallel to the b axis by two `weak' hydrogen bonds and a short Namino...Sgalactose contact.

Synthetic Approaches to Biologically Active C-2-Substituted Benzothiazoles

Numerous benzothiazole derivatives are used in organic synthesis, in various industrial and consumer products, and in drugs, with a wide spectrum of biological activity. As the properties of the benzothiazole moiety are strongly affected by the nature and position of substitutions, in this review, covering the literature from 2016, we focus on C-2-substituted benzothiazoles, including the methods of their synthesis, structural modification, reaction mechanisms, and possible pharmacological activity. The synthetic approaches to these heterocycles include both traditional multistep reactions and one-pot atom economy processes using green chemistry principles and easily available reagents. Special attention is paid to the methods of the thiazole ring closure and chemical modification by the introduction of pharmacophore groups.

Crystal structure of 2-(2,5-dimethoxyphenyl)benzo[d]thiazole

The title compound was synthesized efficiently in the solid state by exploiting pepsin catalysis. The ring systems are nearly coplanar. A short intra­molecular S⋯O=C contact is observed.

The title compound, C₁₅H₁₃NO₂S, was synthesized efficiently in the solid state by exploiting pepsin catalysis. The ring systems are nearly coplanar [inter­planar angle of 5.38 (2)°] with an associated intra­molecular S⋯O=C short contact of 2.7082 (4) Å. The packing involves C—H⋯O, C—H⋯π and π–π contacts.

Crystal structure of 2-(benzo[d]thiazol-2-yl)-3,3-bis(ethylsulfanyl)acrylonitrile

In the title compound, C14H14N2S3, the double-bond system of the acrylonitrile moiety is significantly non-planar, with absolute cis torsion angles of 13.9 (2) and 15.1 (2)°. The ring system and the double bond system subtend an interplanar angle of 11.16 (4)°. The wide angle C—C(CN)=C of 129.40 (12)° may be associated with a balance between planarity and avoidance of a very short S...S contact.

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review

Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation reactions with carbon dioxide (CO₂) are included. Conventional methods with the use of acid and metal catalysts as well as recent green techniques, such as microwave irradiation, the use of ionic liquids, and ultrasound (US) chemistry, which have proven to have many advantages, were found in the review.

Squaraine-Based Optical Sensors: Designer Toolbox for Exploring Ionic and Molecular Recognitions

Small molecule-based chromogenic and fluorogenic probes play an indispensable role in many sensing applications. Ideal optical chemosensors should provide selectivity and sensitivity towards a variety of analytes. Synthetic accessibility and attractive photophysical properties have made squaraine dyes an enticing platform for the development of chemosensors. This review highlights the versatility of modular assemblies of squaraine-based chemosensors and chemodosimeters that take advantage of the availability of various structurally and functionally diverse recognition motifs, as well as utilizing additional recognition capabilities due to the unique structural features of the squaraine ring.

Crystal structure of N'-[2-(benzo[d]thia-zol-2-yl)acet-yl]benzohydrazide, an achiral compound crystallizing in space group P1 with Z = 1

In the mol-ecule of the title compound, C16H13N3O2S, one hydrazinic nitro-gen atom is essentially planar, but the other is slightly pyramidalized. The torsion angle about the hydrazinic bond is 66.44 (15)°. Both hydrazinic hydrogen atoms lie anti-periplanar to the oxygen of the adjacent carbonyl group. The mol-ecular packing is a layer structure determined by two classical hydrogen bonds, N-H⋯O=C and N-H⋯Nthia-zole. The space group is P1 with Z = 1, which is unusual for an achiral organic compound.

Current advances in the synthetic strategies of 2-arylbenzothiazole

Benzothiazole is a privileged scaffold in the field of synthetic and medicinal chemistry. Its derivatives and metal complexes possess a gamut of pharmacological properties and high degree of structural diversity that has proven it vital for the investigation for novel therapeutics. The 2nd position of benzothiazole is the most active site that makes 2-arylbenzothiazole as felicitous scaffolds in pharmaceutical chemistry. The extensive significance of benzo-fused heterocyclic moieties formation has led to broad and valuable different approaches for their synthesis. This review deals with the synthetic approaches developed so far for the synthesis of 2-arylbenzothiazoles. Moreover, this article abridges the publications devoted to the synthesis of this moiety over the last 6 years. This study gives a current precis of research on the fabrication of 2-arylbenzothiazoles through different synthetic pathways and shall be helpful for researchers and scientists who are working in this field to make more potent biologically active benzothiazole-based drugs.

Design and synthesis of a new class of indeno[1,2-b]pyridine thioglycosides

This research reports a novel method for synthesizing a new class of indeno[1,2-b]pyridine thioglycosides. This series of indenopyridine thioglycosides was designed by the reaction of (E)-2-cyano-3-(furan/or thiophene-2-yl)prop-2-enethioamide 1a or 1b with 1-indanone 2 to give the corresponding 2-thiooxo-1H-indeno[1,2-b]pyridine-3-carbonitriles 3a,b. The latter compounds were treated with peracetylated sugar bromides 5 in KOH-acetone to give the corresponding indenopyridine thioglycosides 6a-h. Ammonolysis of the protected indenopyridine thioglycosides 6a-h gave the corresponding free indenopyridine thioglycosides 7a-h. The compounds have been characterized by ¹³C NMR, ¹H NMR and IR spectra.