Microwave-assisted neat synthesis of α-aminophosphonate/phosphinate derivatives of 2-(2-aminophenyl)benzothiazole as potent antimicrobial and antioxidant agents

Green approach to the synthesis of α-aminophosphonate-tetrahydroisoquinoline hybrids and their anti-cholinesterase activity

A series of 19 novel α-aminophosphonate-tetrahydroisoquinoline hybrids were synthesized through a cross dehydrogenative coupling reaction between N-aryl-tetrahydroisoquinolines and dialkylphosphites, using tert-butyl hydroperoxide as oxidazing agent. This simple procedure provided products with high atom economy and moderate to high yields. In vitro cholinesterase inhibitory activity of these compounds was evaluated. All the synthesized compounds showed good to excellent selective inhibition against butyrylcholinesterase. Compound 3bc was found to be the most active derivative with an IC50 of 9 nM. Molecular modelling studies suggested that the inhibitor is located in the peripheral anionic site (PAS) of the enzyme and interacts with some residue of the catalytic anionic site. Kinetic studies revealed that 3bc acts as a non-competitive inhibitor. Predicted ADME showed good pharmacokinetics and drug-likeness properties for most hybrids. Each newly synthesized compound was characterized by IR, 1H NMR, 13C NMR, 31P NMR spectral studies and also HRMS. The results of this study suggest that α-aminophosphonate-tetrahydroisoquinoline hybrids can be promising lead compounds in the discovery of new and improved drugs for the treatment of Alzheimer's disease and related neurodegenerative disorders.

Chromone Containing Hybrid Analogs: Synthesis and Applications in Medicinal Chemistry

The use of privileged scaffolds has proven beneficial for generating novel bioactive scaffolds in drug discovery program. Chromone is one such privileged scaffold that has been exploited for designing pharmacologically active analogs. The molecular hybridization technique combines the pharmacophoric features of two or more bioactive compounds to avail a better pharmacological activity in the resultant hybrid analogs. The current review summarizes the rationale and techniques involved in developing hybrid analogs of chromone, which show potential in fields of obesity, diabetes, cancer, Alzheimer's disease and microbial infections. Here the molecular hybrids of chromone with various pharmacologically active analogs or fragments (donepezil, tacrine, pyrimidines, azoles, furanchalcones, hydrazones, quinolines, etc.) are discussed with their structure-activity relationship against above-mentioned diseases. Detailed methodologies for the synthesis of corresponding hybrid analogs have also been described, with suitable synthetic schemes. The current review will shed light on various strategies utilized for the design of hybrid analogs in the field of drug discovery. The importance of hybrid analogs in various disease conditions is also illustrated.

Design, synthesis and biological evaluation of novel antipyrine based α-aminophosphonates as anti-Alzheimer and anti-inflammatory agent

Herein, a series of novel antipyrine based α-aminophosphonates derivatives were synthesized and characterized. The synthesized derivatives were subjected for in vitro cholinesterase inhibition, enzyme kinetic studies, protein denaturation assay, proteinase inhibitory assay and cell viability assay. For cholinesterase inhibition, the results inferred that the test compounds possess better AChE activity (0.46 to 6.67 µM) than BuChE (2.395 to 12.47 µM). Compound 4j inhibited both AChE and BuChE (IC₅₀ = 0.475 ± 0.12 µM and 2.95 ± 0.16 µM, respectively), implying that it serves as a dual AChE/BuChE inhibitor. Also, kinetic studies revealed that compound 4j exhibits mixed-type inhibition against both AChE and BuChE, with K_i values of 3.003 µM and 5.750 µM, respectively. Further, protein denaturation and proteinase inhibitory assays were used to test in vitro anti-inflammatory potential. It was found that compound 4o exhibited highest activity against protein denaturation (IC₅₀ = 42.64 ± 0.19 µM) and proteinase inhibition (IC₅₀ = 37.57 ± 0.19 µM) when compared to diclofenac. In addition, cell viability assay revealed that active compounds possess no cytotoxicity against N2a cell and RAW 264.7 macrophages. Finally, molecular docking experiments for AChE, BuChE, and COX-2 were conducted to better understand the binding modes of active compounds.Communicated by Ramaswamy H. Sarma.

Synthesis of covalent organic frameworks via Kabachnik-Fields reaction for water treatment

Providing safe and clean domestic water for people is currently one of the greatest worldwide issues. In this context, heavy metal ions and pathogenic microbes are the two major factors in water pollution. The conventional water treatment methods, however, are generally high-energy and high-resource consumptive. Herein, we report, the first of its kind, the room-temperature synthesis of α-aminophosphonate-linked COFs via three-component one-pot in situ Kabachnik-Fields reaction (KF-3CR). Due to the coexistent bioactive α-aminophosphonate and photosensitive porphyrin, the obtained APCOF-1 exhibits highly efficient solar-powered bactericidal and heavy metal ion removal abilities, which allows it to be a promising COF-based multifunctional material for water treatment in an energy- and resource-saving way. Specifically, by incorporating APCOF-1 (up to 50 wt%) with eco-friendly and low-cost chitosan, an APCOF-1 @chitosan aerogel-based helical setup is fabricated via a facile templated freeze-drying approach and it can be a continuous flow-through water purifier model to achieve scaled-up water treatment through adsorptive removal of heavy metal ions and sunlight-driven sterilization. We believe that this research not only can significantly enrich the synthetic methodology of COFs, but also will hopefully bring COFs one step closer to the practical application.

Molecular Environment Effects That Modulate the Photophysical Properties of Novel 1,3-Phosphinoamines Based on 2,1,3-Benzothiadiazole

We report synthesis, crystal structure, and photophysical properties of novel 1,3-phosphinoamines based on 4-amino-2,1,3-benzothiadiazole (NH₂-btd): Ph₂PCH(Ph)NH-btd (1) and Ph₂P(E)CH(Ph)NH-btd, (E = O (2α and 2β·thf), S (3), Se (4)). Chalcogenides 2–4 exhibit bright emissions with a major band at 519–536 nm and a minor band at 840 nm. According to TD-DFT calculations, the first band is attributed to fluorescence, while the second band corresponds to phosphorescence. In the solid state, room temperature quantum yield reaches 93% in the case of the sulphide. The compounds under study feature effects of the molecular environment on the luminescent properties, which manifest themselves in fluorosolvatochromism as well as in a luminescent response to changes in crystal packing and in contributions to aggregation effects. Specifically, transformation of solid 2β·thf to solvate-free 2β either by aging or by grinding causes crystal packing changes, and, as a result, a hypsochromic shift of the emission band. Polystyrene films doped with 2 reveal a bathochromic shift upon increasing the mass fraction from 0.2 to 3.3%, which is caused by molecular aggregation effects.

Naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate

We have previously published new biheterocyclic phospohonic α-amino esters of the 1,2,3-triazole-benzimidazole and 1,2,3-triazole-carbazole type. The aim of the present paper was to describe a new phosponic aminoester bearing a triazole ring substituted in position 5 by an ester group. Thus, according to the same catalytic process used previously, the compound naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate was synthesized with an excellent yield and high regioselectivity via the copper (I)-catalyzed alkyne–azide cycloaddition reaction (CuAAC), using diethyl (α-azido(benzamido)methyl)phosphonate (1) as a dipole and 2- naphthyl propiolate as a dipolarophile (2). The structure of the new compound was fully characterized by 1D (31P, 1H-, 13C-) and 2D (1H-1H and 1H-, 13C-) NMR spectroscopy, IR, and HRMS.

Isatin as a 2-aminobenzaldehyde surrogate: transition metal-free efficient synthesis of 2-(2'-aminophenyl)benzothiazole derivatives

A transition metal-free, convenient, and efficient practical approach has been devised for the synthesis of substituted 2-(2'-aminophenyl)benzothiazoles via a sulfur insertion strategy using isatin derivatives as 2-aminobenzaldehyde surrogates. KI assisted one-pot operation of isatin, arylamines and elemental sulfur resulted in the formation of a C-N and two C-S bonds and cascade cleavage of the isatin ring resulting in the formation of 2-(2'-aminophenyl)benzothiazoles. The significant features of this strategy are the readily available and inexpensive starting materials, broad substrate scope, sustainable reaction conditions and high yield of products. Importantly, the strategy was found to be appropriate for gram scale synthesis (>10 g) of 2-(2'-aminophenyl)benzothiazole derivatives. Moreover, the excellent photophysical properties (ΦF up to 60%) of 2-(2'-aminophenyl)benzothiazole derivatives provide huge scope in materials science.

Design, synthesis and evaluation of new chromone-derived aminophosphonates as potential acetylcholinesterase inhibitor

A series of novel N-substituted α-aminophosphonates-bearing chromone moiety were synthesized and evaluated for acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) activities and antioxidant properties. Porcine pancreatic lipase was employed as a catalyst. Inhibitory activity against AChE ranged between 0.103 and 5.781 µM, whereas for BuChE, activities ranged between 8.619 and 18.789 µM. The results show that among the various synthesized compounds, strongest AChE inhibition was found for the compound containing aliphatic amine analogs, while in case of BuChE, aromatic amines showed better activity as compared to aliphatic amines. Compound 4j was found to be the most potent inhibitor of AChE with an IC₅₀ value of 0.103 ± 0.24 μM and inhibited AChE through mixed-type inhibition. Compound 4j was twofolds more potent than tacrine, 35-folds potent than galantamine and 50-folds potent than rivastigmine. Also, docking study revealed that compound 4j binds to both the peripheral anionic site and catalytic anionic site of AChE and BuChE. The antioxidant activities of synthesized compounds were performed against 2,2-diphenyl-1-picrylhydrazyl and hydrogen peroxide scavenging. DNA nicking activity of selected compounds also suggested that the compounds do not harm plasmid DNA pBR322. Compound 4j also showed significant DNA damage protection activity. Novel N-substituted α-aminophosphonates bearing chromone moiety were synthesized and evaluated for anti-acetylcholinesterase, anti-butyrylcholinesterase, antioxidant and DNA damage activities.

Synthesis carbonic anhydrase enzyme inhibition and antioxidant activity of novel benzothiazole derivatives incorporating glycine, methionine, alanine, and phenylalanine moieties

Thirteen novel benzothiazole derivatives incorporating glycine, methionine, alanine, and phenylalanine were synthesised by facile acylation reactions through benzotriazole or DCC mediated reactions and their structures were identified by 1H-NMR, 13C-NMR, and FT-IR spectroscopic techniques and elemental analysis. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against four human (h) isoforms, hCA I, hCA II, hCA V, and hCA XIII. Some of the synthesised compounds showed good in vitro carbonic anhydrase inhibitory properties, with inhibition constants in the micromolar level. The new amino acid benzothiazole conjugates found to be more effective against hCA V and hCA II inhibition. In vitro antioxidant activities of the novel compounds were determined by DPPH method. Most of the synthesised compounds showed moderate to low antioxidant activities compared to the control antioxidant compounds (BHA and α-tocopherol).