aureus

An internal collection of commercial and synthetically derived small molecule compounds was screened against several drug-resistant bacterial pathogens. Compound 1, a known N, N-disubstituted 2-aminobenzothiazole, was found to be a potent inhibitor of Staphylococcus aureus and several associated clinically relevant strains of methicillin-resistant S. aureus suggesting a possible novel mechanism of inhibition. It failed to show activity in any of the Gram-negative pathogens it was tested in. Evaluation in Escherichia coli BW25113 and Pseudomonas aeruginosa PAO1, as well as in their respective hyperporinated and efflux pump-deletion mutants revealed that activity in Gram-negative bacteria is diminished because this benzothiazole scaffold is a substrate for bacterial efflux pumps. Several analogs of 1 were synthesized to generate basic structure-activity relationships for the scaffold which highlighted that the N-propyl imidazole moiety was critical for the observed antibacterial activity.

A Green Approach to 2-Substituted Benzo- and Naphthothiazoles via N-bromosuccinimide/Bromide-Mediated C(aryl)-S Bond Formation

2-Substituted benzo- and naphthothiazoles have been conveniently prepared from the intramolecular cyclization of phenylthioureas and activated thiobenzanilides or the coupling of isothiocyanates with amines under mild conditions using N-bromosuccinimide/tetrabutylammonium bromide in 1,2-dimethoxyethane (DME) under ambient conditions. The reactions produce moderate to excellent yields with good functional group tolerance and avoid the use of harsh thermal conditions, corrosive reagents, halogenated solvents, toxic metal salts, and expensive metal catalysts, and are amenable to preparations on a gram-scale.

Network Analysis Guided Designing of Multi-Targeted Anti-Fungal Agents: Synthesis and Biological Evaluation

During the ongoing pandemic, there have been increasing reports of invasive fungal disease (IFD), particularly among immunocompromised populations. Candida albicans is one of the most common clinical pathogenic microorganisms which have become a serious health threat to population either infected with Covid-19 or on treatment with immunosuppressant's/broad-range antibiotics. Currently, benzothiazole is a well explored scaffold for anti-fungal activity, especially mercapto substituted benzothiazoles. It is reported that exploring the 2nd position of benzothiazoles yield improved anti-fungal molecules. Therefore, in the current study, lead optimization approach using bioisosteric replacement protocol was followed to improve the anti-fungal activity of an already reported benzothiazole derivative, N-(1,3-benzothiazole-2-yl)-2-(pyridine-3-ylformohydrazido) acetamide. To rationally identify the putative anti-candida targets of this derivative, network analysis was carried out. Complexes of designed compounds and identified putative targets were further analyzed for the docking interactions and their consequent retention after the completion of exhaustive MD simulations. Top seven designed compounds were synthesized and evaluated for in-vitro anti-fungal property against Candida, which indicated that compounds 1.2c and 1.2f possess improved and comparable anti-fungal activity to N-(1,3-benzothiazole-2-yl)-2-(pyridine-3-ylformohydrazido) acetamide and Nystatin, respectively.

Rational assembly of GO-based heterocyclic sulfur- and nitrogen-containing aerogels and their adsorption properties toward rare earth elementals

An aromatic heterocyclic compound, 2-aminobenzothiazole (ABT), was used to decorate graphene oxide (GO) by a facile hydrothermal self-assembly procedure. The developed three-dimensional (3D) GO-ABT composite aerogels could be utilized as high-powered and sustainable adsorbents for the enrichment and recovery of low concentration rare earth elements (REEs) from aqueous solutions. The composition and microstructure of GO-ABT composites were explored various characterization methods. The enrichment properties of GO-ABT composites for REEs were investigated in detail, revealing the existence of S-, N- and -NH₂ in ABT, as well as the carboxyl and hydroxyl groups of GO which might act as the major REE binding sites. The adsorption of GO-ABT composites for low concentration REEs could reach equilibrium in 30 min. Our investigations confirmed that the optimal pH value of GO-ABT composites for REEs was pH 4.0-5.0. For the adsorbent regeneration study, 50.0 mg of GO-ABT_{15:1/120 °C/6 h} composite was used toward 20.0 mL of Er³⁺ solutions. After ten regeneration cycles, the adsorption rates of GO-ABT composites for Er³⁺ remained around 100%, and the desorption rates maintained over 90%. The long-term storage of the adsorbent did not affect its adsorption ability, while desorption rates increased, indicating it possessed relatively higher stability.

Pd Doped on TCH@SBA-15 Nanocomposites: Fabrication and Application as a New Organometallic Catalyst in the Three-Component Synthesis of N-Benzo-imidazo- or -thiazole-1,3-thiazolidinones

In this study, Pd(II)/TCH@SBA-15 nanocomposites were synthesized by the grafting of 3-chloropropyltriethoxysilane and thiocarbohydrazide on SBA-15 and subsequent deposition of palladium acetates through the ligand-metal coordination method. The structure and morphology of this nanoporous nanocomposite was thoroughly identified by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, atomic absorption spectroscopy, and Brunauer-Emmett-Teller instrumental analyses. Furthermore, the catalytic activity of this nanocomposite was investigated in the three-component synthesis of 3-benzimidazolyl or benzothiazoleyl-1,3-thiazolidin-4-ones via a reaction of 2-aminobenzimidazole or 2-aminobenzothiazole, aromatic aldehydes, and thioglycolic acid in an acetone-H2O mixture under green conditions. The Pd/TCH@SBA-15 nanocatalyst is demonstrated to exhibit a high catalyzing activity in the three-component reaction of the synthesis of N-heterocyclic thiazolidinones with good to excellent yields. One of the advantages of the suggested method is the direct application of the thiocarbohydrazide ligand to stabilize Pd nanoparticles through formation of a stable ring complex without creating an additional Schiff base step. Moreover, this organometallic nanocatalyst can be recycled several times with no notable leaching or loss of performance.

Synthesis of biologically active derivatives of 2-aminobenzothiazole

The minireview considers the current trends in the synthesis of some biologically active compounds based on 2-aminobenzothiazole. The presented information covers publications of the last five years.

Modern Approaches to the Synthesis and Transformations of Practically Valuable Benzothiazole Derivatives

The review is devoted to modern trends in the chemistry of 2-amino and 2-mercapto substituted benzothiazoles covering the literature since 2015. The reviewed heterocycles belong to biologically active and industrially demanded compounds. Newly developed synthesis methods can be divided into conventional multistep processes and one-pot, atom economy procedures, realized using green chemistry principles and simple reagents. The easy functionalization of the 2-NH2 and 2-SH groups and the benzene ring of the benzothiazole moiety allows considering them as highly reactive building blocks for organic and organoelement synthesis, including the synthesis of pharmacologically active heterocycles. The review provides a summary of findings, which may be useful for developing new drugs and materials and new synthetic approaches and patterns of reactivity.

Synthesis, SAR, In silico Appraisal and Anti-Microbial Study of Substituted 2-aminobenzothiazoles Derivatives

BACKGROUND

Antimicrobial resistance is a major global health problem, which is being rapidly deteriorating the quality of human health. Series of substituted N-(benzo[d]thiazol-2-yl)-2- (4-(6-fluorobenzo[d]isoxazol-3-yl) piperidin-1-yl)acetamide (3a-j) were synthesized from substituted N-(benzo[d]thiazol-2-yl)-2-chloroacetamide/bromopropanamide (2a-j) and 6-fluoro-3- (piperidin-4-yl)benzo[d]isoxazole (2) and further evaluated for their docking properties and antimicrobial activity.

METHODS

All the synthesized compounds were characterized by FT-IR, NMR and Mass spectral analysis. All compounds were allowed to dock against different antimicrobial targets having PDB ID: 1D7U and against common antifungal target having PDB ID: 1EA1.

RESULTS

The compounds 3d and 3h showed good activity against Methicillin-resistant Staphylococcus aureus (MRSA, resistance Gram-positive bacteria). All synthesized compounds showed good to moderate activity against selected bacterial and fungal microbial strains. If we compared the actual in-vitro antimicrobial activity and in silico molecular docking study, we found that molecules 3i and 3h were more potent than the others.

CONCLUSION

Our current study would definitely pave the new way of designing and synthesis of more potent 2-aminobenzothiazoles derivatives.

Isothioureas, Ureas, and Their N-Methyl Amides from 2-Aminobenzothiazole and Chiral Amino Acids

In this investigation, the reaction of 2-dithiomethylcarboimidatebenzothiazole with a series of six chiral amino-acids was studied. The reaction proceeds through the isolable sodium salt of SMe-isothiourea carboxylates as intermediates, whose reaction with methyl iodide in stirring DMF as solvent affords SMe-isothiourea methyl esters. The presence of water in the reaction leads to the corresponding urea carboxylates as isolable intermediates, whose methyl esters were obtained. Finally, the urea N-methyl amide derivatives were isolated when SMe-isothiourea or urea methyl esters were reacted with methylamine in the presence of water. The structures of synthesized compounds were established by ¹H and ¹³C nuclear magnetic resonance and the structures of SMe-isothiourea methyl esters derived from (l)-glycine, (l)-alanine, (l)-phenylglycine, and (l)-leucine, by X-ray diffraction analysis. This methodology allows to functionalize 2-aminobenzothiazole with SMe-isothiourea, urea, and methylamide groups derived from chiral amino acids to get benzothiazole derivatives containing coordination sites and hydrogen bonding groups. Further research on the biological activities of some of these derivatives is ongoing.

Synthesis, SAR, Molecular Docking and Anti-Microbial Study of Substituted N-bromoamido-2-aminobenzothiazoles

BACKGROUND

Benzothiazoles are reported to have bioorganic and pharmaceutical chemistry applications.

INTRODUCTION

A series of substituted N-bromoamido-2-aminobenzothiazoles was synthesized from substituted anilines via 2-aminobenzothiazoles and it was further evaluated for its antimicrobial activity.

METHODS

All the newly synthesized compounds were characterized by FT-IR, NMR and mass spectra and purity profiles were studied by HPLC analysis. The antimicrobial testing (MIC determination) was newly performed with agar micro-broth dilution method for these analogs.

RESULTS

Among the synthesized compound 3b showed the highest activity with MIC value of 3.12 μg/mL against Bacillus, E. coli, S. aureus and Klebsiella and 6.25 μg/mL against C. albicans. The ADME properties as calculated by using Qikprop were found within acceptable range. Derivatives shows a good-moderate binding affinity towards target Cytochrome P450 14 alpha-sterol demethylase (CYP51) (PDB ID: 1EA1).

CONCLUSION

Our in-silico and in-vitro studies on a series of substituted aminobenzothiazoles may be helpful for further designing of more potent antimicrobials in future.

Synthesis and molecular docking of new roflumilast analogues as preferential-selective potent PDE-4B inhibitors with improved pharmacokinetic profile

In the present work, we designed and synthesized new roflumilast analogues with preferential-selective PDE-4B inhibition activity and improved pharmacokinetic properties. The unsubstituted benzo[d]thiazol-2-yl and -6-yl benzamide derivatives (4a and 6a) showed both good potency and preferential selectivity for PDE-4B. More remarkably, 6c revealed 6 times preferential PDE-4B/4D selectivity with a significant increase of in vitro cAMP and good % inhibition of TNF-α concentration. In addition, the in vitro pharmacokinetics of 6c showed good metabolic stability with in vitro CL_int (5.67 mL/min/kg) and moderate % plasma protein binding (53.71%). This was reflected onto increased in vivo exposure with a half-life greater than roflumilast by 3 folds (21 h) and a C_max value of 113.958 ng/mL. Molecular docking attributed its good activity to its key binding interactions in PDE-4B active site with additional hydrogen bonding with amino acids lining the metal pocket. Summing up, 6c can be considered as suitable candidate for further investigation for the treatment of COPD.

Preparation and Characterization of Novel Polyvinylidene Fluoride/2-Aminobenzothiazole Modified Ultrafiltration Membrane for the Removal of Cr(VI) in Wastewater

Hexavalent chromium is one of the main heavy metal pollutants. As the environmental legislation becomes increasingly strict, seeking new technology to treat wastewater containing hexavalent chromium is becoming more and more important. In this research, a novel modified ultrafiltration membrane that could be applied to adsorb and purify water containing hexavalent chromium, was prepared by polyvinylidene fluoride (PVDF) blending with 2-aminobenzothiazole via phase inversion. The membrane performance was characterized by evaluation of the instrument of membrane performance, infrared spectroscopy (FTIR), scanning electron microscope (SEM), and water contact angle measurements. The results showed that the pure water flux of the PVDF/2-aminobenzothiazole modified ultrafiltration membrane was 231.27 L/m²·h, the contact angle was 76.1°, and the adsorption capacity of chromium ion was 157.75 µg/cm². The PVDF/2-aminobenzothiazole modified ultrafiltration membrane presented better adsorption abilities for chromium ion than that of the traditional PVDF membrane.

Photophysical and Photoprototropic Characteristics of 2-Aminobenzothiazole in β-Cyclodextrin Medium

The formation of stable inclusion complexes between neutral and monocationic species of 2-aminobenzothiazole (2ABT) with β-CDx is observed with significant enhancement in absorbance and fluorescence intensity. The stoichiometry of the 2ABT and 2ABTH^⊕ with β-CDx is found to be 1:1 at pH 6.8 and 1.1. Their binding constant values for neutral and monocationic species are found to be 1239.3 and 1259.2 M^-1, respectively. Lifetime analysis, FT-IR spectral and SEM image analysis strongly supports the formation of the inclusion complex between 2ABT and β-CDx. Photoprototropic study shows that there is no remarkable difference in the pK _a and pK _a* in aqueous and β-CDx media, which is rules out the formation of the inclusion complex with -NH₂ group of 2ABT inside the cavity of β-CDx i.e., the -NH₂ group of 2ABT is in aqueous environment. Based on stoichiometry, binding constant and acidity constant values, the structure of the 1:1 complex is proposed.

Intramolecular Rearrangement of α-Amino Acid Amide Derivatives of 2-Aminobenzothiazoles

We have found that α-amino acid amide derivatives of 2-aminobenzothiazoles undergo a time-dependent, thermal rearrangement in which the amine group attacks the 2-position carbon of the thiazole ring to form a 5,5-spiro ring system. This is followed by sulfur leaving and air oxidation to the corresponding symmetrical disulfide. The isolated yields of such products are quite high (>70%) if there is conformational bias to further promote the intramolecular reaction such as for the 2-aminobenzothiazole amides derived from proline or 4-aminopiperidine-4-carboxylic acid. This rearrangement has not been described previously for α-amino acid amide derivatives of 2-aminobenzothiazoles. However, a related reaction involving 2-semicarbazido benzothiazoles has been recently reported.

Synthesis, Characterization, and Biological Evaluation of certain 6-methyl-2(3H)-benzo-1, 3-thiazolyl-1'-ethylidene-2-(o, p- Substituted Acetophenones) Hydrazine Analogs

In the present study, five new derivatives (GG4 to GG8) of benzothiazoles were synthesized and evaluated against Staphylococcus aureus (MTCC 737), Pseudomonas aeruginosa (MTCC 424), Escherichia coli (MTCC 1687), and yeast-like fungi Candida tropicalis. p-Toluidine on treatment with ammonium thiocynate formed 2-benzothiazolamines (II), which on reaction with hydrazine hydrate formed a hydrazino derivative (III). Compounds GG4 to GG8 were synthesized by reacting the hydrazine derivative with different acetophenones. All the synthesized compounds were identified by IR and (1)H-NMR, and antimicrobial activity was performed on the synthesized compounds. Presence of NO(2), Br, OCH(3), and Cl groups to the substituted benzothiazole enhanced the antibacterial and antifungal activities.