Bioactive Thiazine and Benzothiazine Derivatives: Green Synthesis Methods and Their Medicinal Importance

Micelle-mediated synthesis of quinoxaline, 1,4-benzoxazine and 1,4-benzothiazine scaffolds from styrenes

A range of heterocycles based on quinoxalines, 1,4-benzoxazines and 1,4-benzothiazines have been accessed from styrenes by reacting them with benzene-1,2-diamine, 2-aminophenol and 2-aminothiophenol respectively in micellar medium. This reaction occurring in a less explored cetylpyridinium bromide (CPB) micellar medium operates in the presence of NBS through a tandem hydrobromination-oxidation cascade, converting styrenes to phenacyl bromides. Its subsequent nucleophilic addition with aromatic 1,2-dinucleophiles and further transformations led to the formation of heterocyclic constructs. The locus of the reaction site was confirmed through NMR studies and the types of interactions between the CPB and solubilizates were established by DFT calculations.

Design, synthesis, and evaluation of 1,4-benzothiazine-3-one containing bisamide derivatives as dual inhibitors of Staphylococcus aureus with plausible application in a urinary catheter

In this study, 1,4-benzothiazine-based bisamide derivatives, a new class of antibacterial agents targeting bacterial peptide deformylase (PDF), were designed and synthesized to combat Staphylococcus aureus infection. Molecular modeling of the designed molecules showed better docking scores compared to the natural product actinonin. Bioactivity assessment identified two derivatives with promising antibacterial activity in vitro. The stability of the most active molecule, 8bE, was assessed using molecular dynamics (MD) simulation. Significantly, compound 8bE could also inhibit the S. aureus biofilm at low concentrations. Furthermore, the capability of the synthesized molecule to inhibit S. aureus biofilm formation on medical devices like urinary catheters is also demonstrated.

Mechanistic Investigations on the Interaction of Morita-Baylis-Hillman Ketones with 2-Aminothiophenol

The reaction of Morita-Baylis-Hillman ketones with 2-aminothiophenol mediated by Cs2CO3 results in an oxidative cyclization to 2,2-disubstituted dihydro-1,4-benzothiazines, with the structure of the product indicating the occurrence of an aza-Michael addition along the pathway. In contrast, in the absence of a base, the parent compounds interact to produce a thia-Michael adduct instead. A deeper mechanistic study improved our understanding of the apparent contradiction and provided insight into the base-dependent switch in reactivity.

Potential anti-amoebic effects of synthetic 1,4-benzothiazine derivatives against Acanthamoeba castellanii

A rare but lethal central nervous system disease known as granulomatous amoebic encephalitis (GAE) and potentially blinding Acanthamoeba keratitis are diseases caused by free-living Acanthamoeba. Currently, no therapeutic agent can completely eradicate or prevent GAE. Synthetic compounds are a likely source of bioactive compounds for developing new drugs. This study synthesized seventeen 1,4-benzothiazine derivatives (I -XVII) by a base-catalyzed one-pot reaction of 2-amino thiophenol with substituted bromo acetophenones. Different spectroscopic techniques, such as EI-MS, 1H-, and 13C NMR (only for the new compounds), were used for the structural characterization and conformation of compounds. These compounds were assessed for the first time against Acanthamoeba castellanii. All compounds showed anti-amoebic potential in vitro against A. castellanii, reducing its ability to encyst and excyst at 100 μM. Compounds IX, X, and XVI showed the most potent activities among all derivatives and significantly reduced the viability to 5.3 × 104 (p < 0.0003), 2 × 105 (p < 0.006), and 2.4 × 105 (p < 0.002) cells/mL, respectively. The cytotoxicity profile revealed that these molecules showed lower to moderate cytotoxicity, i.e., 36 %, 2 %, and 21 %, respectively, against human keratinocytes in vitro. These results indicate that 1,4-benzothiazines showed potent in vitro activity against trophozoites and cysts of A. castellanii. Hence, these 1,4-benzothiazine derivatives should be considered to develop new potential therapeutic agents against Acanthamoeba infections.

Base-Promoted Synthesis of S-Arylisothiazolones via Intramolecular Dehydrative Cyclization of α-Keto-N-acylsulfoximines

A base (Et3N)-promoted synthesis of 1,4-diarylisothiazolones from α-keto-N-acylsulfoximines has been achieved. The reaction proceeds via α-hydrogen abstraction from sulfoximine, followed by an intramolecular nucleophilic attack at the keto carbonyl to form a tert-hydroxy isothiazolone intermediate. The 1,4-substituted isothiazolone is obtained after dehydration via an E1cB path. This one-pot synthesis of isothiazolinones has a broad substrate scope, has a high atom economy, and provides products with good yields. The ΔELUMO-HOMO is calculated using Gaussian 16 at the B3LYP/6-31G(d,p) level of theory.

Green Synthetic Strategies and Pharmaceutical Applications of Thiazine and its Derivatives: An Updated Review

Thiazines are a sizable class of organic heterocycles that are notable for their skeletal versatility and relative chemical simplicity, making them among the most flexible sources of biologically active compounds. The term "green synthesis" refers to implementing energy-efficient procedures for the nature-friendly production of materials and chemicals using green solvents, catalysts, and suitable reaction conditions. Considering the importance of green chemistry and the outstanding therapeutic profile of thiazines, the present work was designed to review the recent advances in green chemistry-based synthetic strategies of thiazine and its derivatives. The green synthetic approaches, including microwave-assisted, ultrasound-assisted, and various other synthetic methods for thiazine and its derivatives, were discussed and generalized. In addition, applications of thiazine and its derivatives in pharmaceutical sciences were explained with examples of marketed drugs.The discussed sustainable synthetic methods for thiazines and their derivatives could be useful in developing other medicinally important lead molecules. They could also aid in developing new synthetic schemes and apparatuses that may simplify chemical manufacturing processes and enable novel reactions with minimal by-products while questing for optimal, green solvents. This review can help anyone interested in this fascinating class of heterocycles to make decisions about selecting targets and tasks for future research.

Green Synthetic Methods of Oxazine and Thiazine Scaffolds as Promising Medicinal Compounds: A Mini-review

Medical researchers have paid close attention to the green synthesis of oxazine and thiazine derivatives since they provided a lead molecule for the creation of numerous possible bioactive compounds. This review provides more information on green synthesis, which will be very helpful to researchers in creating the most effective, affordable, and clinically significant thiazine and oxazine derivatives that are anticipated to have strong pharmacological effects. This has resulted in the identification of several substances with a wide range of intriguing biological functions. This article's goal is to examine the numerous green chemical processes used to create oxazine and thiazine derivatives and their biological activity. We anticipate that researchers interested in oxazine and thiazine chemicals will find this material to be useful. We anticipate that medicinal chemists looking for new active medicinal components for drug discovery and advance progress will find this review of considerable interest.

The Multifaceted Opportunities Provided by the Pheomelanin-Inspired 1,4-Benzothiazine Chromophore: A Still-Undervalued Issue

1,4-Benzothiazines are the main building blocks of the naturally occurring pheomelanin pigments, and their chromophoric properties have been strongly related to the well-known phototoxicity of these pigments, partly responsible for the high incidence of melanoma and other skin cancers in red-haired people. However, some peculiar features of the 1,4-benzothiazine chromophore could be functionally exploited in several sectors. Within this context, in this perspective, an overview of the very recently reported applications of the 1,4-benzothiazine chromophore in pH sensing, filter permeability control, smart packaging, electrochromic device fabrication, bioimaging, photocatalysis, and HPLC detection systems is provided, together with a brief presentation of recently developed synthetic approaches to the 1,4-benzothiazine scaffold, with the aim of emphasizing the still-undervalued multifunctional opportunities offered by this class of compounds.

The Benzothiazine Core as a Novel Motif for DNA-Binding Small Molecules

A new series of 4H-1,3-benzothiazine dyes were prepared and fully characterized in an aqueous medium. Benzothiazine salts were synthesized either through the classical synthetic pathway using Buchwald-Hartwig amination or through economical and environmentally friendly electrochemical synthesis. The latest synthetic approach employs successful electrochemical intramolecular dehydrogenative cyclization of N-benzylbenzenecarbothioamides to form 4H-1,3-benzothiazines. 4H-1,3-Benzothiazines were evaluated as novel DNA/RNA probes. Through the use of several methods such as UV/vis spectrophotometric titrations, circular dichroism and thermal melting experiments, the binding of four benzothiazine-based molecules to polynucleotides was examined. Compounds 1 and 2 acted as DNA/RNA groove binders, thus suggesting the potential of these compounds as novel DNA/RNA probes. This is a proof-of-concept study and will be expanded to include SAR/QSAR studies.

A Bioinspired Synthesis of 1,4-Benzothiazines by Selective Addition of Sulfur Nucleophiles to ortho-Quinones

Herein, we report a bioinspired approach to the synthesis of 1,4-benzothiazines by drawing inspiration from the biosynthesis of pheomelanin pigments (pheomelanogenesis). In this context, general conditions for the regioselective coupling reaction between ortho-quinones and thiols were developed. The mild conditions proved amenable to a wide scope of both thiol and ortho-quinone coupling partners while simultaneously suppressing redox-exchange. The utility of this methodology was demonstrated by a synthesis of 1,4-benzothiazines, following a biomimetic, oxidative cyclization.

Antiparasitic Activity of Fluorophenyl-Substituted Pyrimido[1,2-a]benzimidazoles

A series of fourteen pyrimido[1,2-a]benzimidazole compounds was prepared by straightforward heterocyclic chemistry and oxidation methods. The new pyrimidobenzimidazole derivative 2a with a 3-fluorophenyl substituent was identified as a new antiparasitic compound showing excellent activities against Leishmania major parasites. 2a was highly active against L. major promastigotes and amastigotes with EC₅₀ values in the nanomolar concentration range. Compound 3b was less active than 2a against L. major, but more active against Toxoplasma gondii with considerable selectivity. Hence, two promising and selective antiparasitic drug candidates 2a and 3b for the treatment of two parasitic diseases were identified, which can be prepared by green chemistry methods using simple one-pot reactions and oxidation procedures, respectively.

Study of Interactions Between 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine and Human DNA by Theoretical, Spectroscopic and Viscometric measurements

From the last few years mode of interactions between drugs and DNA is an attractive research area as it bridges chemistry, molecular biology and medicinal science. Interactions between small heterocyclic molecules and human DNA is a noteworthy feature in pharmacology for investigation of drugs mechanism and designing of more effective and target specific drugs with fewer side effects. The present research work focuses on the theoretical investigations of 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine (SASA) by using Gaussian (16 W) software to predict optimized geometry, HOMO-LUMO gap, bond length, bond angle, dihedral angle, electronic and vibrational spectra. Possible reaction site observed in SASA was C_7, C₉ and C₁₈ as these atoms show maximum charge density. Later the interactions of SASA with human DNA was explored spectroscopic investigations and viscometric investigations at physiological buffers of pH of 4.7 (stomach pH) and 7.4 (blood pH) respectively. Maximum absorbance between SASA-DNA complex was observed in buffer solution of pH 3.4 at wavelength of 370 nm, whereas at 7.4 has maximim absorbance between. Spectroscopic results reflects the bathochromic and hyperchromic shift succeeding the addition of human DNA. During viscosity measurement, intercalation and electrostatic mode of interaction were detected at low and high concentration of drug in solution respectively. Increase in the value of rate constant was observed with the increase in concentration of drug. Larger values of rate constant were observed at pH 7.4 in comparison to pH 3.5. Rate constant, thermodynamic parameters and viscometric analysis prefers the intake of SASA via blood.

Design, Synthesis and Pharmacological Evaluation of 2-(3-BenzoyI-4-Hydroxy-1,1-Dioxido-2H-Benzo[e][1,2]thiazin-2-yI)-N-(2-Bromophenyl) Acetamide as Antidiabetic Agent

PURPOSE

The present study is based on screening new and potent synthetic heterocyclic compounds as anti-diabetic drugs using various computational tools, lab experiments, and animal models.

METHODS

A potent synthetic compound 2-(3-benzoyl-4-hydroxy-1,1-dioxido-2H-benzo[e][1,2]thiazin-2-yl)-1-(2-bromophenyl) acetamide (FA2) was checked against diabetes and screened via enzyme inhibition assays, enzyme kinetics against alpha-glucosidase and alpha-amylase. Protein-ligand interaction was analyzed via molecular docking and toxicological analysis via ADMET. Experimental animals were used to examine the compound FA2 safety, delivery, and check various biochemical tests related to diabetes like fasting glucose sugar, cholesterol, triglyceride, HbAc1, creatinine, and insulin level. Histography of liver, kidney, and pancreas was also performed.

RESULTS

Results showed that FA2 had binding energy of -7.02 Kcal/mol and -6.6 kcal/mol against α-glucosidase (PDB ID: 2ZE0) and α-amylase (PDB ID: 1B2Y), respectively. Moreover, in vitro enzyme inhibition assays and enzyme kinetics against α-glucosidase and α-amylase were performed, and FA2 showed IC50 at 5.17 ± 0.28 µM and 18.82 ± 0.89 µM concentrations against α-glucosidase and α-amylase, respectively. Kinetics studies showed that the FA2 compound impeded α-glucosidase and α-amylase as a non-competitive mode of inhibition with Ki' values -0.320 ± 0.001 and 0.141 ± 0.01, respectively. FA2 was further analyzed on alloxan-induced mice for 21 days. Biochemical tests (fasting glucose sugar, cholesterol, triglyceride, HbAc1, creatinine, and insulin levels) and histological examination of liver and kidney showed that the FA2 compound showed better results than acarbose. Histology of pancreas found to show the maintenance of normal pancreatic acini and Langerhans islets in FA2 treated mice compared to acarbose and nontreated diabetic controls.

CONCLUSION

Investigating anti-diabetic potential of FA2 compound showed that the selected benzothiazine derivative has tremendous importance in reducing dose concentration and side effects.

Effect of tricyclic 1,2-thiazine derivatives in neuroinflammation induced by preincubation with lipopolysaccharide or coculturing with microglia-like cells

Background

Alzheimer’s disease (AD) is considered the most common cause of dementia among the elderly. One of the modifiable causes of AD is neuroinflammation. The current study aimed to investigate the influence of new tricyclic 1,2-thiazine derivatives on in vitro model of neuroinflammation and their ability to cross the blood–brain barrier (BBB).

Methods

The potential anti-inflammatory effect of new tricyclic 1,2-thiazine derivatives (TP1, TP4, TP5, TP6, TP7, TP8, TP9, TP10) was assessed in SH-SY5Y cells differentiated to the neuron-like phenotype incubated with bacterial lipopolysaccharide (5 or 50 μg/ml) or THP-1 microglial cell culture supernatant using MTT, DCF-DA, Griess, and fast halo (FHA) assays. Additionally, for cultures preincubated with 50 µg/ml lipopolysaccharide (LPS), a cyclooxygenase (COX) activity assay was performed. Finally, the potential ability of tested compounds to cross the BBB was evaluated by computational studies. Molecular docking was performed with the TLR4/MD-2 complex to assess the possibility of binding the tested compounds in the LPS binding pocket. Prediction of ADMET parameters (absorption, distribution, metabolism, excretion and toxicity) was also conducted.

Results

The unfavorable effect of LPS and co-culture with THP-1 cells on neuronal cell viability was counteracted with TP1 and TP4 in all tested concentrations. Tested compounds reduced the oxidative and nitrosative stress induced by both LPS and microglia activation and also reduced DNA damage. Furthermore, new derivatives inhibited total COX activity. Additionally, new compounds would cross the BBB with high probability and reach concentrations in the brain not lower than in the serum. The binding affinity at the TLR4/MD-2 complex binding site of TP4 and TP8 compounds is similar to that of the drug donepezil used in Alzheimer's disease. The ADMET analysis showed that the tested compounds should not be toxic and should show high intestinal absorption.

Conclusions

New tricyclic 1,2-thiazine derivatives exert a neuroregenerative effect in the neuroinflammation model, presumably via their inhibitory influence on COX activity and reduction of oxidative and nitrosative stress.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00414-8.

Derivatives of benzo-1,4-thiazine-3-carboxylic acid and the corresponding amino acid conjugates

Herein, we present the synthesis and utilization of derivatives of 4H-benzo[b][1,4]thiazine-3-carboxylic acid. These benzothiazine compounds were assembled via the coupling of aminothiols and bromopyruvates. Oxidative dimerization of these starting materials was also observed and the corresponding benzothiazine dimers were isolated. Moreover, the coupling of benzothiazines with amino acids was realized. In doing so, an enantioselective synthesis of the nonproteinogenic amino acid 2-amino-3-propylhexanoic acid was accomplished.

Gold-Catalyzed 1,3-Thiazine Formation and Uncommon Tautomer Isolation

This work represents the first example of a gold-catalyzed formation of 1,3-thiazine/1,3-thiazinane by means of a catalytic approach and further uncommon isolation of the two tautomers. The developed protocol gives rise to a broad scope of 1,3-thiazine derivatives with excellent yields in short reaction times. Interestingly, different isomers could be obtained depending on the state of the compound, and in the crystal state the 1,3-thiazinane isomer is obtained, while in solution the 1,3-thiazine is the unique isomer. This work represents an interesting approach for the synthesis of potential biologically relevant molecules and a crucial precedent in tautomerism isolation and characterization.

Design, Synthesis, and Fungicidal Evaluation of Novel 1,3-Benzodioxole-Pyrimidine Derivatives as Potential Succinate Dehydrogenase Inhibitors

A series of novel 1,3-benzodioxole-pyrimidine derivatives were designed and synthesized. The in vitro bioassay indicated that compounds 4e, 4g, 4n, 5c, and 5e displayed excellent fungicidal activities against test fungal strains. Especially, in the in vitro experiments, 5c exhibited a broad spectrum of fungicidal activity against Botrytis cinerea, Rhizoctonia solani, Fusarium oxysporum, Alternaria solani, and Gibberella zeae with EC₅₀ values of 0.44, 6.96, 6.99, 0.07, and 0.57 mg/L, respectively, which were significantly more potent than those of positive control boscalid (EC₅₀: 5.02, >50, >50, 0.16, and 1.28 mg/L). In vivo testing on tomato fruits and leaves showed that 5c displayed considerable protective and curative efficacy against A. solani. Scanning electron microscopy analysis indicated that 5c possessed a strong ability to destroy the surface morphology of mycelia and seriously interfere with the growth of the fungal pathogen. In the in vitro enzyme inhibition assay, 5c exhibited pronounced succinate dehydrogenase (SDH) inhibitory activity with an IC₅₀ value of 3.41 μM, equivalent to that of boscalid (IC₅₀: 3.40 μM). In addition, fluorescence quenching experiment further confirmed the strong interaction of 5c with SDH. Through chiral resolution, 5c was separated into two enantiomers. Among them, (S)-5c exhibited stronger fungicidal activity (EC₅₀: 0.06 mg/L) and SDH inhibitory (2.92 μM) activity than the R-enantiomer (EC₅₀: 0.17 mg/L and SDH IC₅₀: 3.68 μM), which was in accordance with the molecular docking study (CDOCKER Interaction Energy for (R)-5c and (S)-5c: -28.23 and -29.98 kcal/mol, respectively). These results presented a promising lead for the discovery of novel SDHIs as antifungal pesticides.

Synthesis of 2,2-Disubstituted Dihydro-1,4-benzothiazines from Morita-Baylis-Hillman Ketones by an Oxidative Cyclization

An oxidative cyclization ensued upon interaction of Morita-Baylis-Hillman (MBH) ketones with 2-aminothiophenol in the presence of Cs₂CO₃, resulting in the formation of new 2,2-disubstituted dihydro-1,4-benzothiazines. The reaction features an aza-Michael addition and an oxidative cyclization involving the formation of a carbon-sulfur bond and works well over a wide range of MBH ketones to deliver the dihydrobenzothiazines in good yields in reasonable reaction times under mild conditions.

Exploring of novel 4-hydroxy-2H-benzo[e][1,2]thiazine-3-carbohydrazide 1,1-dioxide derivative as a dual inhibitor of α-glucosidase and α-amylase: Molecular docking, biochemical, enzyme kinetic and in-vivo mouse model study

Diabetes mellitus (DM) is a metabolic disorder that leads to hyperglycemia due to improper insulin secretion. The study aims to investigate the anti-diabetic potential of benzothiazine derivatives. Molecular docking and Molecular Dynamics simulation study revealed that Compound S6 (4-hydroxy-2H-benzo[e][1,2]thiazine-3-carbohydrazide 1,1-dioxide) and S7 (4-Hydroxy-2-methyl-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxide) had less conformational changes during MD simulation analysis at 100 ns. Compound S6 and S7 showed potent activity with IC50 values of 5.93 μM, 6.91 μM and 75.17, 29.10 μM for α-glucosidase and α-amylase respectively and competitive type of inhibition was observed during enzyme kinetic study with a low value of Ki and Ki' for α-glucosidase and α-amylase, respectively. S6 has the lowest Ki (0.0736) and Ki' (-0.0982) for α-glucosidase. Furthermore, in vivo studies were carried out to distinguish the effects of the drug on the body. Histology analysis on mice model showed that compound S6 has a low necrosis rate in the liver, kidney, and pancreas compared to S7. Biochemical results of S6 revealed lower sugar level (112 mg/dL), increase insulin secretion (23, 25 μM/L), and low level of cholesterol (80, 85 mg/dL) and creatinine (1.6, 1.4 mg/dL). The results conclude that compound S6 is a new anti-diabetic agent that minimizes hyperglycemia complications.

Novel 1,2-thiazine-pyridine hybrid: Design, synthesis, antioxidant activity and molecular docking study

Background & objectives:

1,2-thiazine and pyridine heterocycles drew much attention due to their biological activities including antioxidant activity. Based upon fragment based drug design, novel pyrido[1,2]thiazines 9a-c, thiazolidinopyrido[1,2]thiazines 10a-c and azetidinopyrido[1,2]thiazines 11a-c were designed and prepared.

Methods:

These novel derivatives 9a-c, 10a-c and 11a-c were subjected to screening for their antioxidant activity via various assays as DPPH radical scavenging potential, reducing power assay and metal chelating potential.

Results:

All the assayed derivatives exhibited excellent antioxidant potential and the tested compounds 9a, 9b, 10a, 10b, 11a and 11b exhibited higher DPPH scavenging potential (EC50 = 32.7, 53, 36.1, 60, 40.6 and 67 µM, respectively) than ascorbic acid (EC50 = 86.58 µM). While targets 9a, 10a and 11a (RP50 = 52.19, 59.16 and 52.25 µM, respectively) exhibited better reducing power than the ascorbic acid (RP50 = 84.66 µM). Computational analysis had been utilized to prophesy the bioactivity and molecular properties of the target compounds.

Conclusion:

To predict the binding manner of the novel derivatives as antioxidants, in-silico docking study had been performed to all the newly prepared compounds inside superoxide dismutase (SOD) and catalase (CAT) active site. The most active antioxidant candidate 9a (EC50 = 32.7 µM, RP50 = 52.19 µM) displayed excellent binding with Lys134 amino acid residing at Cu-Zn loop of SOD with binding energy score = -7.54 Kcal/mol thereby increase SOD activity and decrease reactive oxygen species.

From Thioureas to Thioquinolines through Isolated Benzothiazines by Gold Catalysis

New benzothiazine heterocycles have been formed from thiourea derivatives by using different gold catalysts. The catalyst and the conditions were optimised towards the selective synthesis of six‐membered benzothiazine heterocycles, characterised by X‐ray diffraction. Interestingly, these organic compounds evolved under gold catalysis in basic medium to achieve the formation of amino thioquinolines through an unprecedented aromatisation process of the heterocycle. The reaction was also carried out stoichiometrically by reaction with gold complexes to afford thioquinolines coordinated to the gold fragment. Benzothiazine, amino thioquinoline heterocycles and gold‐derived species have a great potential for biological applications.

Transition-Metal-Catalyzed C-H Bond Functionalization of Arenes/Heteroarenes via Tandem C-H Activation and Subsequent Carbene Migratory Insertion Strategy

The past decade has witnessed tremendous developments in transition-metal-catalyzed C-H bond activation and subsequent carbene migratory insertion reactions, thus assisting in the construction of diverse arene/heteroarene scaffolds. Various transition-metal catalysts serve this purpose and provide efficient pathways for an easy access to substituted heterocycles. A brief introduction to metal-carbenes has been provided along with key mechanistic pathways underlying the coupling reactions. The purpose of this review is to provide a concise knowledge about diverse directing group-assisted coupling of varied arenes/heteroarenes and acceptor-acceptor/donor-acceptor diazo compounds. The review also highlights the synthesis of various carbocycles and fused heterocycles through diazo insertion pathways, via C-C, C-N and C-O bond forming reactions. The mechanism usually involves a C-H activation process, followed by diazo insertion leading to subsequent coupling.

Unconventional approaches for the introduction of sulfur-based functional groups

Organosulfur compounds have a pivotal role in the functionalities of many natural products, pharmaceuticals and organic materials. For these reasons, the search for new methodologies for the formation of carbon-sulfur bonds has been the object of intensive work for organic chemists. However, the proposed strategies suffer from various drawbacks, such as volatility, toxicity, and instability of the sulfur sources or the use of VOC solvents. In this review, we summarise the recent protocols which have the goal of obtaining sulfones, thioethers, thiazines, thiazepines and sulfonamides in an unconventional and/or sustainable way. The use of starting materials less invasive and toxic with respect to the traditional reagents, alternative solvents such as water, ionic liquids or deep eutectic solvents, the exploitation of ultrasound and electrochemistry, increasing the efficiency of the process, are reported. Moreover, representative reaction mechanisms are also discussed.

Fused benzo[1,3]thiazine-1,2,3-triazole hybrids: Microwave-assisted one-pot synthesis, in vitro antibacterial, antibiofilm, and in silico ADME studies

In this paper, we report an efficient one-pot three-component reaction sequences comprising Cu(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC) followed by Cu-catalyzed arylation of resulting 1,2,3-triazole in the presence of ionic liquid [Emim]BF₄ under microwave conditions involving. The newly synthesized derivatives were screened for in vitro antibacterial inhibition potency against both gram +ve and gram -ve strains. Among the tested compounds, 4f exhibited significant inhibition activity with MIC value 3.12 µg/mL against B. subtilis and S. epidermidis which is two-fold higher than the standard ciprofloxacin (6.25 µg/mL) and also displayed equipotent activity to that of the positive control against S. aureus with MIC value 6.25 µg/mL. Conjugates of the series viz. 3f and 4b against S. aureus, and 4e against E. coli have also displayed promising results with MIC values 6.25 µg/mL which is comparable to the ciprofloxacin. Also we report the anti-biofilm profiles for the potent compounds and it was observed from the results that the active derivatives 4b and 4f were not only potent antibacterial agents but also efficient inhibitors of B. subtilis and S. aureus biofilm growth. Furthermore, in silico-ADME and pharmacokinetic profiles demonstrated the druggability of the hybrids.

Evaluation of the Physicochemical, Antioxidant, and Antibacterial Properties of Tunichrome Released from Phallusia nigra Persian Gulf Marine Tunicate

The aim of this study was to evaluate the physicochemical, nutraceutical, antioxidant, and antibacterial properties of tunichrome released from Persian Gulf tunicate (Phallusia nigra). For this purpose, molecular weight (SDS-PAGE), amino acid profile, chemical composition (GC-MS), mineral composition, functional groups (FTIR), total phenol content (TPC), total flavonoid content (TFC), antioxidant activity, and antimicrobial properties were investigated. The results showed that tunichrome contained a high amount of essential amino acids (i.e., Lys = 32.24 mg/100 g) and essential minerals. According to GC-MS results, tunichrome had different antioxidant and antimicrobial components. The TPC and TFC of tunichrome were 0.55 mg GA/g and 0.21 mg quercetin/100 g, respectively. Tunichrome showed higher antioxidant activity than ascorbic acid, and its radical scavenging activity values were increased from 30.28 to 82.08% by increasing concentration from 50 to 200 ppm. Inhibition zones of Staphylococcus aureus, Bacillus cereus, Salmonella enterica, and Escherichia coli O157:H7 were 14, 18, 17, and 15 mm, respectively. Moreover, the minimum inhibitory concentration values of tunichrome for S. aureus, Bacillus cereus, S. enterica, and E. coli O157:H7 were 1.17, 0.59, 0.59, and 1.17 mg/ml, respectively. The minimum bacterial concentrations were 2.34, 1.17, 1.17, and 2.34 mg/ml for S. aureus, Bacillus cereus, S. enterica, and E. coli O157:H7, respectively. These results showed that tunichrome of Phallusia nigra has excellent biological effects as a bioactive compound for food fortification.

Evaluation of 1,2-Benzothiazine 1,1-dioxide Derivatives In Vitro Activity towards Clinical-Relevant Microorganisms and Fibroblasts

The global concern related with growing number of bacterial pathogens, resistant to numerous antibiotics, prone scientific environment to search for new antimicrobials. Antiseptics appear to be suitable candidates as adjunctive agents to antibiotics or alternative local treatment option aiming to prevent and treat infections. 1,2-benzothiazines are considered one the most promising of them. In this research twenty 1,2-benzothiazine 1,1-dioxide derivatives were scrutinized with regard to their biological activity. Three of them are new. For evaluation of compounds' activity against microbial pathogens, disk diffusion method and serial microdilution method was applied. To establish the cytotoxicity profile of tested 1,2-benzothiazines 1,1-dioxides derivatives, the cytotoxicity assay using fibroblasts L292 was performed. Antimicrobial activity of all tested compounds against Gram-positive Staphylococcus aureus and Enterococcus faecalis strains was higher than antimicrobial activity of DMSO solvent, which possesses antimicrobial activity itself. Gram-negative P. aeruginosa, E. coli and K. pneumoniae have shown susceptibility only to compounds 3e, 7i and 7l. None of tested compounds was effective against C. albicans. Compound 6g has demonstrated the strongest antimicrobial potency (MIC = 0.00975 mg/mL) among compounds of series 6. Compounds of series 7, namely 7d, 7f, 7g had the lowest minimum inhibitory concentration (MIC). Compound 7f displayed also the lowest cytotoxic effect against fibroblast cell line among series 7 compounds. All tested derivatives displayed lower MIC against Gram-positive bacteria than commercially applied antiseptic, povidone iodine, which MIC value range for tested Gram-positive bacteria was 1.56-6.25 mg/mL.

Visible light initiated amino group ortho-directed copper(i)-catalysed aerobic oxidative C(sp)-S coupling reaction: synthesis of substituted 2-phenylbenzothiazoles via thia-Wolff rearrangement

A facile amino group ortho-directed visible-light-driven copper-catalysed aerobic oxidative C(sp)-S coupling reaction of a dimer of 2-aminothiophenol with terminal alkynes was achieved. This photochemical reaction shows an excellent conversion and chemoselectivity towards the formation of C(sp)-S coupling and has been employed for a wide range of thiol dimers, and alkynes. Furthermore, the synthetic utility of the synthesized alkynyl sulfides was demonstrated as a direct method for the construction of 2-phenylbenzothiazoles from the corresponding alkynyl sulfides via "thia-Wolff rearrangement" using AgNO3 and visible light using 9-mesityl-10-methylacridinium ions (Acr+-Mes) as photoredox catalyst system.

Assessment of the Antitumor Potentiality of Newly Designed Steroid Derivatives: Pre-Clinical Study

Cancer is recognized as one of the most prevalent contributors to mortality in several nations and it remains one of the common health issues globally. In particular, hepatocellular carcinoma (HCC) has become a public health problem along with the increase of hepatitis B (HBV) and hepatitis C (HCV) virus infections. Based on this fact, our study goaled to synthesize newly hybrid drugs containing heterocyclic rings incorporated to steroid moiety and to examine the potential antitumor activity of the newly designed heterosteroid derivatives against HCC induced in animal model. Several heterocyclic steroids were synthesized 2-7 and confirmed via the analytical and spectral data (IR, ¹H NMR¹³C NMR and Mass spectroscopy). Compounds 3, 4, and 5 were chosen to be investigated as anticancer agents in HCC rat model by means of validated biomarkers (alfa –fetoprotein, endoglin, lipocali-2 and heat shock protein-70). Following administration of compounds 3, 4 or 5, availability of the active tumor marker molecules was significantly dropped and a substantial decrease of the angiogenic and inflammatory mediators was also evident. These findings were supported by the histological examination of liver tissue. Taken together, this study indicates the potential anticancer activity of the newly synthesized heterosteroid derivatives against HCC in vivo. The antitumor activity of these compounds was likely attributable to modulating some signal transduction pathways involved in tumorigenesis, angiogenesis and inflammation.

Molecular docking and simulation of Zika virus NS3 helicase

The Zika virus (ZIKV) has gained attention for the last few years due to the congenital microcephaly and Guillain–Barre Syndrome that resulted in humans. The non-structural protein-3 (NS3) helicase of ZIKV play an important role in viral RNA replication. In this article, we performed hundred nanosecond molecular dynamics simulation and molecular docking of the NS3 helicase of ZIKV with 1,4-benzothiazine derivatives. The root mean square deviation (RMSD) analyses showed the stability of the NS3 helicase. The simulation showed that the flexible and rigid domains of the protein play a crucial role during the RNA replication process. All such domains with ligand binding pockets can be targeted for drug design. The molecular docking showed that the strong hydrogen bonding and arene-cation interactions are responsible for the binding between NS3 and 1,4-benzothiazine derivatives, which provides a new dimension for potent drug design for ZIKV.

A metal- and base-free domino protocol for the synthesis of 1,3-benzoselenazines, 1,3-benzothiazines and related scaffolds

Efficient protocols have been described for the synthesis of 1,3-benzoselenazines, 1,3-benzothiazines, 2-aryl thiazin-4-ones and diaryl[b,f][1,5]diazocine-6,12(5H,11H)-diones. These transformations were successfully driven towards the product formation under mild acid catalyzed reaction conditions at room temperature using 2-amino aryl/hetero-aryl alkyl alcohols and amides as substrates. The merits of the present methods also rely on the easy access of rarely explored bioactive scaffolds like 1,3-benzoselenazine derivatives, for which well-documented methods are rarely known in the literature. A broad range of substrates with both electron-rich and electron-deficient groups were well-tolerated under the developed conditions to furnish the desired products in yields up to 98%. The scope of the devised method is not only restricted to the synthesis of 1,3-benzoselenazines, but it was also further extended towards the synthesis of 1,3-benzothiazines, 1,3-benzothiazinones and the corresponding eight membered N-heterocycles such as diaryl[b,f][1,5]diazocine-6,12(5H,11H)-diones.

Intramolecular dehydrogenative C–S bond coupling of thioamides to form 1,3-benzothiazines under metal-free conditions

A new protocol for the synthesis of 1,3-benzothiazines was developed through direct intramolecular dehydrogenative C–S bond coupling.

Increasing the Strength and Production of Artemisinin and Its Derivatives

Artemisinin is a natural sesquiterpene lactone obtained from the Artemisia annua herb. It is widely used for the treatment of malaria. In this article, we have reviewed the role of artemisinin in controlling malaria, spread of resistance to artemisinin and the different methods used for its large scale production. The highest amount of artemisinin gene expression in tobacco leaf chloroplast leads to the production of 0.8 mg/g of the dry weight of the plant. This will revolutionize the treatment and control of malaria in third world countries. Furthermore, the generations of novel derivatives of artemisinin- and trioxane ring structure-inspired compounds are important for the treatment of malaria caused by resistant plasmodial species. Synthetic endoperoxide-like artefenomel and its derivatives are crucial for the control of malaria and such synthetic compounds should be further explored.