Microwave-assisted synthesis and biological evaluation of carbazole-based chalcones,aurones and flavones

A new class of chalcones, aurones and flavones derived from carbazole is designed as potential antimicrobial and antioxidant agents. Synthesis of (Z)-2-((9-ethyl-9H-carbazol-3-yl)methylene)benzofuran-3(2H)-ones and 2-(9-ethyl-9H-carbazol-3-yl)-4H-chromen-4-ones was carried out by the oxidation of (E)-3-(9-ethyl-9H-carbazol-3-yl)-1-(2-hydroxyphenyl)prop-2-en-1-ones under microwave irradiation and conventional heating. All the newly synthesized compounds were characterized on the basis of IR, ¹H NMR, ¹³C NMR, mass and analytical data. All the synthesized compounds were evaluated for their antibacterial, antifungal and antioxidant activities. Synthesized compounds were screened in vitro for antibacterial activity against two gram-positive bacterial strains like Staphylococcus aureus and Bacillus subtilis and two gram-negative bacterial strains like Escherichia coli and Klebsiella pneumonia and antifungal activity by inhibitory action against three fungal strains like Fusarium oxysporum, Aspergillus niger and Aspergillus flavus. The synthesized compounds were also evaluated for their DPPH radical scavenging activity. All the newly synthesized compounds have shown good antibacterial, antifungal and antioxidant activities.     

Synthesis,characterization, and antimicrobial activity of some new coumarin derivatives

A number of new [(4-methyl-2-oxo-2H-chromen-7-yl)amino]methylcoumarins (5a–c), benzofuran (6), and benzoxazol (7) were synthesized through the reaction of 7-amino-4-methylcoumarin (1) with a number of organic halides. In addition, series of N-substituted 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetohydrazide (11a–h) and (12a–d) were prepared from the reaction of 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetohydrazide (8) with corresponding heteroaryl/alkyl halides (2–4, 9, and 10). The synthesized compounds were characterized by elemental analysis and by spectroscopic techniques such as ¹H-NMR, ¹³C-NMR, and mass spectrometry and were tested for their in vitro antimicrobial activity. The newly synthesized compounds exerted significant inhibitory activity against the growth of tested bacterial strains and a few of them are found to be potent antimicrobial agents.     

Synthesis and antimicrobial activity of some new 4-triazolylmethoxy-2H-chromen-2-one derivatives

4-(5-Aryl-4H-[1,2,4]triazol-3-ylmethoxy)-2H-chromen-2-ones have been synthesized by the one pot cyclocondensation reaction of 2-(2-oxo-2H-chromen-4-yloxy)acetohydrazide with aromatic/heterocyclic aldehydes in the presence of ammonium acetate in acetic acid. The structures of all the new compounds have been established on the basis of their analytical and spectral data. These compounds were also evaluated for their antibacterial and antifungal activity against various strains of bacteria and fungi and some are found to possess significant antimicrobial activity when compared with ciprofloxacin and miconazole.     

Synthesis and leishmanicidal evaluation of sulfanyl- and sulfonyl-tethered functionalized benzoate derivatives featuring a nitroimidazole moiety

A series of new nitroimidazole-containing derivatives was synthesized by coupling of 2-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethylthio]ethanol with diversely substituted benzoic acids. Upon treatment with m-CPBA, 12 of these sulfanyl compounds were further oxidized to their sulfonyl analogs. All the 26 synthetic compounds were examined for in vitro activity against Leishmania (V.) braziliensis and Leishmania (L.) mexicana, and some of them displayed an efficient antileishmanial activity. Among the compounds tested, the catecholic derivative 2-{[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]sulfanyl}ethyl 3,4-dihydroxybenzoate ( 9a , LC₅₀ = 13 and 11 µM) and the pyrogallolic derivative 2-{[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]sulfanyl}ethyl 3,4,5-trihydroxybenzoate ( 9b , LC₅₀ = 4 and 1 µM) were the most active ones against the two Leishmania strains.     

Synthesis, antimicrobial activity, and molecular modeling of novel 4-(3-(4-benzylpiperazin-1-yl)propoxy)-7-methoxy-3-substituted phenyl-2H-chromen-2-one

A series of novel 4-(3-(4-benzylpiperazin-1-yl)propoxy)-7-methoxy-3-substituted phenyl-2H-chromen-2-one (7a–7j) were synthesized by the reductive amination of 7-methoxy-3-phenyl-4-(3-piperizin-1-yl-propaxy)chromen-2-one (6) with different substituted aromatic aldehydes by using sodium cyanoborohydride in methanol. The newly synthesized compounds were purified and their structures were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectroscopy. The representative analogs were screened for in vitro antimicrobial activity. The compounds exhibited significant antibacterial and antifungal activity as that of standards. The data was further compared with structure-based investigations using docking studies with the crystal structure of oxidoreductase (1XDQ and 3QLS) protein organisms. The estimated score by genetic algorithm was found to have a good correlation with the experimental inhibitory potency of the derivatives.     

Benzimidazole derivatives: synthesis, leishmanicidal effectiveness, and molecular docking studies

Leishmanolysin GP63 is a zinc metalloprotease, expressed at the surface of Leishmania promastigotes. Studies on this protein are hindered as only a limited number of effective non-toxic inhibitors of this drug target are known. Present study describes the identification of a variety of 2-aryl- and 5-nitro-2-arylbenzimidazoles as new GP63 inhibitors. All the compounds were tested for in vitro activity against the promastigote form of Leishmania major and showed very good activity. 2-(Thiophen-2-yl)-1H-benzimidazole (19) and 2-(1H-indol-3-yl)-5-nitro-1H-benzimidazole (34) with IC₅₀ value of 0.62 μg/mL were identified as lead of this library. Molecular docking studies were performed on binding site of GP63 to study the binding mode of compounds. The results of both in vitro and in silico studies clearly indicated that benzimidazoles may serve as new drug candidates in the combat against leishmaniasis.     

Antimicrobial activity of Schiff bases of coumarin-incorporated 1,3,4-oxadiazole derivatives: an in vitro evaluation

A series of 3-{5-[(E)-(substituted benzylidene) amino]-1,3,4-oxadiazol-2-yl}-2H-chromen-2-ones (4a–r) were synthesized by the reaction of 3-(5-amino]-1,3,4-oxadiazol-2-yl}-2H-chromen-2-one with different substituted benzaldehydes to form Schiff bases of coumarin-incorporated 1,3,4-oxadiazole derivatives. The structures of the compounds were confirmed on the basis of their elemental analysis and spectral data. The compounds were screened against bacterial strains Staphylococcus aureus NCTC (10418), Escherichia coli NCTC (6571), and fungal strain Candida albicans ATCC (10231). Ciprofloxacin and Ketoconazole were used as standards. The test compounds and standards were evaluated at 100 μg/ml concentration. DMF (N,N-dimethylformamide) was used as solvent and control. Most of the synthesized compounds possess significant antimicrobial activity. Compound (4m) without any substitution of the phenyl ring which is attached to 1,3,4-oxadiazole moiety showed highly significant in vitro growth inhibition against S. aureus and E. coli, while as compound (4g) with para N(CH₃)₂ showed highly significant in vitro growth inhibition against C. albicans.     

Microwave-assisted synthesis,molecular docking and antimicrobial activity of novel 2-(3-aryl,1-phenyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-4-yl)-8<Emphasis Type="Italic">H</Emphasis>-pyrano[2,3-f]chromen-4-ones

An efficient synthetic protocol of microwave-assisted synthesis of some novel 2-(3-aryl,1-phenyl-1H-pyrazol-4-yl)-8H-pyrano[2,3-f]chromen-4-ones 6a–j in excellent yields starting from 3-(3-aryl,1-phenyl-1H-pyrazol-4-yl)-1-(5-hydroxy-2H-chromen-6-yl)-propenones 5a–j was described. This approach offers the advantages of short reaction time (3–5 min), mild reaction conditions, high yields (80–88 %) and convenient operation. All the synthesized compounds were tested in vitro for their antimicrobial activity. The compounds 5h (Ar = 3-ethoxyphenyl), 6c (Ar = 4-chlorophenyl), 6e (Ar = 4-hydroxyphenyl) and 6i (Ar = 3,4-methoxyphenyl) were found to be potent against tested bacterial strains, and compounds 5g (Ar = 4-ethoxyphenyl), 6c (Ar = 4-chlorophenyl) and 6i (Ar = 3,4-methoxyphenyl) were found to be potent against tested fungal strains. The final compounds were subjected to molecular docking studies for the inhibition of enzyme DNA gyrase. The in silico molecular docking results are matching with the in vitro antimicrobial studies, and they may be considered as good inhibitor of DNA gyrase.     

In vitro antimicrobial and antimycobacterial activity of some chalcones and their derivatives

In this study, novel series of chalcone derivatives, namely, 4-[4-(3-phenyl-acryloyl)-phenylamino]-chromen-2-one (5a–k) have been synthesized from the intermediate 4-(4-acetyl-phenylamino)-chromen-2-one (4). Cyclization reaction of chalcone (5a–k) with hydrazine hydrate, guanidine nitrate, and malononitrile gives the corresponding 4-[4-(1-acetyl-5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)-phenylamino]-chromen-2-one (6a–k), 4-[4-(2-amino-6-phenyl-pyrimidin-4-yl)-phenylamino]-chromen-2-one (7a–k), and 2-amino-6-[4-(2-oxo-2H-chromen-4-ylamino)-phenyl]-4-phenyl-nicotinonitrile (8a–k) derivatives were synthesized. The newly synthesized compounds were evaluated for their antimycobacterial activity and antimicrobial activity against eight bacteria (S. aureus, B. cereus, E. coli, P. aeruginosa, K. pneumoniae, S. typhi, P. vulgaris, and S. flexneri) and four fungi (A. niger, C. albicans, A. fumigatus, and A. clavatus).     

Synthesis and Antitumor Activity of Some New 2-Chloroethylnitrosoureas

The synthesis of a series of N-(2-chloroethyl)-N′-(9H-xanthen-9-yl)-N-nitrosoureas and N-(2-chloroethyl)-N′-(9H-thioxanthen-9-yl)-N-nitrosoureas is described. The title compounds were evaluated against NSCLCN6 L16 bronchial epidermoid carcinoma in vitro and some of them were found to be active. N-(2-chloroethyl)-N′-(2-methoxy-9H-xanthen-9-yl)-N-nitrosourea ( 8e ) was active against leukemia P388 tumor system in mice.     

New glycosides from <Emphasis Type="Italic">Dracocephalum tanguticum</Emphasis> maxim

Four new glycosides, luteolin-7-methoxy-3′-O-(3″-O-acetyl)-β-D-gluco pyranuronic acid-6″-methyl ester (1), benzyl-6-[(2E)-2-butenoate]-β-D-glucopyranoside (2), 2-methoxy-4-(2-propen-1-yl)penyl-6-acetate-β-D-glucopyranoside (3), and 2-methoxy-4-(2-propen-1-yl)penyl-6-[(2E)-2-butenoate]-β-D-glucopyranoside (4), along with benzyl-β-D-glucopyranoside (5), 2-methoxy-4-(2-propen-1-yl)penyl-β-D-glucopyranoside (6), and pectolarigenin (7), were isolated from the whole plant of Dracocephalum tanguticum Maxim. The structures of 1-4 were elucidated by detailed spectroscopic analyses, including HR-ESI-MS and 2D NMR spectroscopic data. The inhibitory effects against nitric oxide production in LPS-stimulated RAW264.7 cells of all seven compounds were also evaluated.     

Synthesis, characterization, and biological evaluation of certain 1,3-thiazolone derivatives bearing pyrazoline moiety as potential anti-breast cancer agents

A series of 5-arylidene-2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-1,3-thiazol-4(5H)-ones were synthesized and screened for their in vitro antitumor activity against human breast adenocarcinoma cell line (MCF-7). Five of the test compounds exhibited good antitumor activity superior to the reference drug, doxorubicin, with IC₅₀ range 1.4–2.3 μM. Among the test compounds, 2-[3,5-bis(4-chlorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]-5-(2-methoxybenzylidene)-1,3-thiazol-4(5H)-one (3i) was found to show the most potent anticancer activity.     

Naphthoherniarin: an unusual coumarin derivative from Ruta graveolens

The roots of RUTA GRAVEOLENS L. afforded the coumarin derivative, 7-methoxy-6-(5,8-dioxo-7-methoxy-3-methyl-5,8-dihydronaphthalen-1-yl)-chromen-2-one, named naphthoherniarin. The structure was elucidated by spectroscopic methods.     

About the conformations of alpha,beta-diunsaturated ketones

Substituted 1-(cyclohexenyl)-3-phenylpropen-1-ones, 1-(2-furyl)-3-phenylpropen-1-ones, and 1-(2-thienyl)-3-phenylpropen-1-ones, ketones with 1,4-pentadien-3-one structure, prefer in solution, and at room temperature, according to 1H NMR and IR investigations the s-trans/s-cis conformation. For some compounds the participation of other conformers in the equilibrium could be demonstrated. These results were obtained by a qualitative study of 25 derivatives in different solvents, and comparison with results from MM+, PM3, AM1 or MMX calculations.     

Synthesis and characterization of new types of 2-(6-methoxy-2-naphthyl)propionamide derivatives as potential antibacterial and antifungal agents

A series of novel 2-(6-methoxy-2-naphthyl)propionamide derivatives have been efficiently synthesized in excellent yields via the reaction of naproxenoyl chloride with different amino compounds. Most of the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Most of the compounds showed significant antibacterial and antifungal activities, reaching, in certain cases, the same level of antimicrobial activity as the standard antibacterial agent Ampicilline and antifungal agent Flucanazole. N-(4-(N-arylsulfamoyl)phenyl)-2-(6-methoxynaphthalen-2-yl)propanamide (4a–c), 4-(4-fluorobenzylidene)-2-(1-(6-methoxynaphthalen-2-yl)ethyl)oxazol-5(4H)-one (10b), 2-(6-methoxynaphthalen-2-yl)-N-((5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl)propanamide (12), and N-((4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl)-2-(6-methoxynaphthalen-2-yl)propanamide (13) were found to be the most potent compounds against most of the tested strains. The antimicrobial activity was further supported by using MIC technique. Structure activity relationship studies revealed several matching pairs.     

Compounds from Gum Ammoniacum with Acetylcholinesterase Inhibitory Activity

The use of herbal medicinal preparations in dementia therapy has been studied based on experience from traditional medicine. A dichloromethane extract of gum ammoniacum, the gum-resin from Dorema ammoniacum D. Don had shown acetylcholinesterase (AChE) inhibitory activity in a previous study. The aim of this study was the isolation and characterization of the active compounds from this resin. The extract was investigated by a respective colorimetric microplate assay and the active zones were identified via TLC bioautography and isolated using several chromatographic techniques. The structures of the active components were characterized by one- and two-dimensional ¹H and ¹³C NMR spectroscopy and mass spectrometry as (2′S,5′S)-2′-ethenyl-5′-(3-hy-droxy-6-methyl-4-oxohept-5-en-2-yl)-7-methoxy-2′-methyl-4H-spiro[chromene-3,1′-cyclopentane]-2,4-dione (1), which is an analogue of doremone A and a new natural compound, and as (2′S,5′R)-2′-ethenyl-5′-[(2R,4R)-4-hydroxy-6-methyl-3-oxohept-5-en-2-yl]-7-methoxy-2′-methyl-4H-spiro[chromene-3,1′-cyclo-pentane]-2,4-dione (2 = doremone A), (4E,8E)-1-(2,4-dihydroxyphenyl)-5,9,13-trimethyltetradeca-4,8,12-trien-1-one (3 = dshamirone), and 4,7-dihydroxy-3-[(2E,6E)-3,7,11-trimethyldodeca-2,6,10-trien-1-yl]-2H-chromen-2-one (4 = am-moresinol). Dshamirone turned out to be the most active compound with an IC₅₀ value for AChE inhibitory activity of 23.5 μM, whereas the other substances showed weak activity. The concentrations of the analytes in the resin were determined by HPLC as 3.1%, 4.6%, 1.9%, and 9.9%, respectively.     

Synthesis and biological activity studies of new hybrid molecules containing tryptamine moiety

The synthesis of N′-(4-substitutedphenylsulfonyl)-2-{4-[2-(1H-indol-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}acetohydrazides (3a–c), 2-{4-[2-(1H-indol-3-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-aryl methylidene acetohydrazides (4a–f) and 4-[2-(1H-indol-3-yl)ethyl]-5-(4-substitutedbenzyl)-2-[(5-sulfanyl-1,3,4-oxadiazol-2-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-ones (5a, b) was performed starting from the corresponding acid hydrazides (2a, b) which was reported earlier. The treatment of 1,3,4-oxadiazole derivatives (5a, b) with hydrazine hydrate produced 4-amino-5-sulfanyl-4H-1,2,4-triazol-3-yl derivatives (6a, b). Then, compound 6b was converted to the corresponding Schiff base (7) by the treatment with anisaldehyde. The synthesis of 5-(4-chlorobenzyl)-4-[2-(1H-indol-3-yl)ethyl]-2-[(4-benzyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (8) and 5-(4-methylbenzyl)-4-[2-(1H-indol-3-yl)ethyl]-2-[(4-benzyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (10) was carried out by the reaction of acid hydrazides (2a, b) with aryl iso(thio)cyanates either via the formation of the intermediates (9a, b) (for 10) or direct cyclization (for 8). 1,3-Oxa(thia)zol-2(3H)-ylidene]acetohydrazide derivatives (11a, b) were obtained by the reaction of 9a, b with 4-chlorophenacyl bromide. All newly synthesized compounds were screened for their antimicrobial activities and some of which was found to be active against the test microorganisms.     

Synthesis and antibacterial evaluation of 6-azapyrimidines with α-methylene-γ-(4-substituted phenyl)-γ-butyrolactone pharmacophores

Abstract  

A series of 6-substituted 2-[(4-methylene-5-oxo-2-(4-substituted phenyl) tetrahydrofuran-2-yl)methyl]-1,2,4-triazine-3,5(2H,4H)-diones (5, 6) and 2,4-bis[(4-methylene-5-oxo-2-(4-substituted phenyl) tetrahydrofuran-2-yl)methyl]-1,2,4-triazine-3,5(2H,4H)-diones (9, 10) were designed, synthesized, and evaluated for antibacterial activity against Gram-positive and Gram-negative microorganisms. The synthesis of these compounds involved the Reformatsky-type reaction between ethyl α-(bromomethyl)acrylate and the proper ketones. Among these compounds, 2-[(4-methylene-5-oxo-2-phenyl tetrahydrofuran-2-yl)methyl]-1,2,4-triazine-3,5(2H,4H)-dione (5a) is the most active compound and shown the selective inhibition activity against Proteus vulgaris.