Synthesis of 6,8-dichloroquinolones utilizing new method and evaluation of their antibacterial activities

Several 6,8-dichloroquinolone analogues were synthesized from the key intermediate compound of 2,3,4,5-tetrachlorobenzene carbonyl chloride,which was obtained from the starting material of tetrachlorophthalic anhydride.Their in vitro antibacterial activities were evaluated.As a result of this study,compounds 21c and 21d were twofold more potent than ciprofloxacin (CPFX) and norfloxacin (NFLX) against Staphylococcus aureus-9,and with the same potent as CPFX and NFLX while against Escherichia coli-2,but were less potent than references in against Pseudomonas aeruginosa-17.     

Nano-Cuo–Au-catalyzed solvent-free synthesis of α-aminophosphonates and evaluation of their antioxidant and α-glucosidase enzyme inhibition activities

A new green and efficient method has been developed for the synthesis of α-aminophosphonates through one-pot three-component Kabachnik–Fields reaction. It involves the reaction of a 2-aminophenol with different substituted aromatic aldehydes and dimethyl phosphite in the presence of nanocopper oxide–gold (CuO–Au) catalyst under solvent-free conditions at 60?°C. Nano-CuO–Au catalyst was found to have many advantages like high activity, simple workup, and good (87%) to very high yields (96%). The products were characterized by IR, ¹H, ¹³C, and ³¹P NMR spectra and elemental analysis. All the synthesized compounds were screened for in vitro antioxidant and α-glucosidase inhibition activities. The compound 4b showed higher 2,2-diphenyl-1-picrylhydrazyl and H₂O₂ radical scavenging activity and compound 4e showed higher NO radical scavenging activity than the standard ascorbic acid. The compound 4j has much higher α-glucosidase enzyme inhibition activity than the standard acarbose.     

An unusual new reaction of α-olefins with magnesiumn-alkyl derivatives catalyzed by Cp2ZrCl2

The reaction of organomagnesium compounds (OMC) containing alkyl radicals of normal structure with -olefins, resulting in the formation of alkenylorganomagnesium compounds and accompanied by hydride transfer was discovered and systematically investigated. A scheme providing for the formation of zirconacyclopentane complexes was proposed for the mechanism of the reaction.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1187–1196, May, 1992.     

Efficient one-pot synthesis of β-phosphono malonates and 2-amino-4H-chromen-4-ylphosphonate derivatives by ethylenediamine diacetate-catalyzed three-component reactions

One-pot three-component reactions of arylaldehyde or salicylaldehyde with malononitrile (or ethylcyanoacetate) and triethyl phosphite are carried out in the presence of ethylenediamine diacetate (EDDA) as a catalyst for the synthesis of biologically interesting β-phosphono malonates and 2-amino-4H-chromen-4-ylphosphonate derivatives. The value of this method lies in its mild reaction catalyst and conditions, good yields, and ease of handling.     

Staudinger ketene–imine [2+2] cycloaddition of novel azomethines to synthesize biologically active azetidinone derivatives and their in vitro antimicrobial studies

Since considerable intrigue has been focused on azetidinone (β-lactam) compounds for their wide range antimicrobial activity, the present study focuses on the synthesis of new series of azetidinone compounds. The reaction between the novel azomethine and α-haloester in the presence of Zn impetus and benzene resulted into the formation of desired azetidinone derivative by [2+2] cycloaddition involving imine–ketene. The reaction has also been studied in the presence of diverse Lewis acids such as Zn(OTf)₂, ZnCl₂, Cu(OTf)₂, TiCl₄, and BF₃.Et₂O. The effect of such Lewis acids also enhance the yield of the desired product. Moreover, the structure of the isolated products was also affirmed by spectral analysis (Fourier-transform infrared [FT-IR] spectroscopy, proton nuclear magnetic resonance [¹H NMR], carbon-13 nuclear magnetic resonance [¹³C NMR], and high-resolution mass spectrometry [HRMS]). Furthermore, the antibacterial activity of synthesized compounds has been screened in vitro against different pathogenic bacterial and fungus species. Inspection of the results uncovered that all of the newly synthesized compounds individually display varying degrees of inhibitory impacts on the development of the tested bacterial species, thus, they might be considered as medication possibility for bacterial pathogens. The azomethine exhibited an expansive range of antibacterial activity against Gram-negative Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, and Acinetobacter baumannii and Gram-positive Staphylococcus aureus bacterial strains and antifungal activity against Candida albicans, Candida tropicalis, and Candida parapsilosis bacterial strain. The result demonstrated that the β-lactam subordinates have good antibacterial and antifungal activities on microscopic organisms.     

Chemical composition and antioxidant, α-glucosidase inhibitory and antibacterial activities of three Echeveria DC. species from Mexico

Three Echeveria species from Sinaloa, Mexico (Echeveria craigiana, Echeveria kimnachii and Echeveria subrigida) were analyzed for their content of antioxidant compounds (β-carotene, ascorbic acid, α-tocopherol, total phenolics and flavonoids) and the in vitro antioxidant (DPPH, ABTS, ORAC and β-carotene bleaching [β-CBM]), α-glucosidase inhibitory and antibacterial activities. The studied Echeveria species showed high α-tocopherol content (2.9–9.0 mg/100 g f.w.) and total phenolics as Gallic Acid Equivalents (GAE) (152.2–400.5 mg GAE/100 g f.w.). Antioxidant activities of the three Echeveria methanol extracts (ME) were higher than those of other well-known plants with this property; the activities of E. craigiana (ABTS, 65.91 μmol ET/g f.w.) and E. subrigida (β-CBM, 79.3%) were remarkable. The Echeveria ME showed stronger α-glucosidase inhibition (IC₅₀ 25.21–50.57 μg/mL) than acarbose (IC₅₀ 3.59 mg/mL) as well as high antibacterial activity (Minimal Inhibitory Concentrations, MICs ⩽ 1 mg/mL), mainly against Gram positive bacteria. The results showed the three Echeveria species had components/biological activities with high potential for food/pharmacological uses and could be exploited by sustainable management schemes.     

Solvent-free sonochemical kabachnic-fields reaction to synthesize some new α-aminophosphonates catalyzed by nano-BF3•SiO2

To obtain a rapid, efficient synthesis of some new α-aminophosphonates, ultrasonic irradiation has been applied to the reaction mixtures containing amine, aromatic or heteroaromatic aldehydes and triethyl phosphite. The Kabachnik-Fields reaction was performed by using nano-BF₃?SiO₂ as a recyclable catalyst under solvent free conditions. Key advantages of this procedure consist in the eco-friendly and highly efficient reaction conditions, high yields, an easy work-up procedure, short reaction times and solvent free conditions. All title compounds were characterized by spectral and elemental analysis. They were further screened for their in vitro antioxidant activity by the DPPH, O^2? and NO methods. The majority of the title compounds showed good antioxidant activity when compared with the standard antioxidants.     

A novel and easy route to 1,3,4-thiadiazine derivatives via the three-component reaction of phenylhydrazine, α-bromo aryl ketones and aryl isothiocyanates

The three-component condensation of phenylhydrazine, α-bromo aryl ketones and aryl isothiocyanates leading to 1,3,4-thiadiazine derivatives is described.     

A novel regio-and stereo-specific hydrohalogenation reaction of 2-alkynoic acids and their derivatives

The nucleophilic hydrohalogenation of 2-alkynoic acids anti their derivatives byheating with lithium halides iu HOAc afforded the thermodynamically unfavorable 3-halo-2 (Z)-alkenoic acids and their derivatives stereospecifically     

Complexation of new active antibacterial adamantan derivatives with β CD: Preparation and characterization of complexes study of the thermotropic properties of pure and complex form with dipalmitoyl phosphatidylcholine bilayers

-Cyclodextrin (CD) complexes of I1-8, I1-10, I1-12, were prepared, isolated and characterized in solid and liquid form. Their thermotropic effects were studied by inserting them in DPPC bilayers both in pure and complexed forms. The results have shown that the presence of I1-8 causes spliting, broadening and lowering of the phase transition of DPPC bilayers. Their effects are more significant when I1-0 and I1-12 are inserted. These differential effects are eliminated when the above studied three molecules are incorporated in a complex form with CD in DPPC bilayers. The obtained results suggest that the bromine salts in the bilayer are likely to remain in the complex form rather than released in the membrane.     

Investigation on the inclusion behaviour of baicalein with β-cyclodextrin and derivatives and their antioxidant ability study

The formation of the complexes of baicalein (Ba) with β-cyclodextrin (β-CD) and β-CD derivatives (HP-β-CD and Me-β-CD) was studied by UV–vis absorption spectroscopy, fluorescence method, nuclear magnetic resonance spectroscopy and phase-solubility measurement. The solid–inclusion complexes of Ba with CDs were synthesised by the co-precipitation method. The characterisations of the solid–inclusion complexes have been proved by infrared spectra and differential scanning calorimetry. Experimental conditions including the concentration of various CDs and media acidity were investigated in detail. The results suggested that the inclusion ratio of HP-β-CD with Ba was the highest among the three kinds of CDs. The binding constants (Ks) of the inclusion complexes were determined by fluorescence method and phase-solubility measurement. Kinetic studies of DPPH√ with Ba and CDs complexes were also done. The results indicated that the Ba/HP-β-CD complex was the most reactive form.     

Cascade reaction of β,γ-unsaturated α-ketoesters with phenols in trityl chloride/TFA system. Highly selective synthesis of 4-aryl-2H-chromenes and their applications

The treatment of β,γ-unsaturated α-ketoesters with phenols in the presence of trityl chloride and 4 ? molecular sieves in refluxing trifluoroacetic acid afforded 4-aryl-2H-chromenes in high yields, in which a reverse of the regiochemistry of J?rgensen-Rutjes chromane synthesis was observed. The isolation of 4H-chromene intermediates, confirmed by single-crystal X-ray analysis, indicates that the early stage of the reaction involves a Friedel-Crafts alkylation/cyclodehydration processes. Stirring of the 4H-chromene intermediate with trityl chloride in deuterotrifluoroacetic acid under reflux afforded the 2H-chromene and triphenylmethane in high yields, which implies the late stage of the reaction involves a hydrogen transfer process. Highly selective derivation of the hydroxyl esters to the corresponding hydroxyl amides, amino acids, amino esters and Friedel-Crafts adducts was further accomplished. Our endeavors will lead to a better understanding of the controlling elements behind their structural motifs. The products were confirmed unambiguously from their spectra and by single-crystal X-ray analysis.     

Reaction of 2-alkoxycarbonylmethyl derivatives of δ2-oxazoline and δ2-imidazoline and their tautomers with 4-nitrobenzonitrile N-oxide

It was established that 2-alkoxycarbonylntethylene derivatives of oxazolidine and imidazolidine react readily with 4-nitrobenzonitrile N-oxide; the reaction takes place at the methylidyne carbon atom to give intermediate oximes, which can then undergo cyclization to isoxazoles. Their tautomers —benzimidazole and ² -oxazoline derivatives —react with considerably greater difficulty; in the first case the reaction takes place at a different center, viz., the ring nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 681–684, May, 1991.     

Metal-free one-pot synthesis of quinoline-2,4-carboxylates via a molecular iodine-catalyzed three-component reaction of arylamines,ethyl glyoxylate,and α-ketoesters

A simple and metal-free method has been developed for the construction of quinoline-2, 4-carboxylates under mild conditions via a molecular iodine-catalyzed three-component tandem reaction of arylamines, ethyl glyoxylate, and α-ketoesters. The present protocol provides a convenient and attractive approach to various quinoline-2, 4-carboxylates in moderate to good yields with excellent functional group tolerance.     

Synthesis of enantiomerically pure α-amino-β-hydroxy-cyclobutanone derivatives and their transformations into polyfunctional three- and five-membered ring compounds

Ketenes readily cycloadded to (R)-tert-butyldihydrooxazole 2a-d to yield enantiomerically pure bicyclic cyclobutanones. The cycloadditions proceeded with unusual regiochemistry giving predominantly or exclusively protected α-amino-β-hydroxycyclobutanone derivatives. The adducts could be converted into a variety of interesting enantiopure intermediates equipped with many functional groups: α-amino-β-hydroxy cyclopropane carboxylic acid derivatives, α-amino-β-hydroxy succinic acid derivatives, α-amino-β-hydroxy lactones and lactams derivatives.     

Reactions of cyclopentanone, γ-butyrolactone,and their derivatives with α-hydroxyethyl radicals

The interaction of cyclopentanone, 2-cyclopentenone, 1,3-cyclopentanedione, 3-methyl-1,2-cyclopentanedione, γ-butyrolactone, 2(5H)-furanone, ascorbic acid, and 5,6-O-isopropylidenyl-2,3-O-dimethylascorbic acid with α-hydroxyethyl radicals (α-HER) generated during the radiolysis of deaerated ethanol has been studied in the continuous irradiation mode. The test compounds, except γ-butyrolactone, oxidize α-HER. 2(5H)-Furanone and 2-cyclopentenone give hydroxyethylation products via the free-radical chain mechanism. In contrast to 2(5H)-furanone and 2-cyclopentenone, ascorbic and 5,6-O-isopropylidenyl-2,3-O-dimethyl-L-ascorbic acids are weaker oxidants for α-HER and attach these radicals at the multiple carbon-carbon bonds.     

Synthesis and biological evaluation of carbohydrate appended hydrazinocyclopentenes with potent glycation and α-glucosidase inhibition activities

Synthesis and biological evaluation of novel alkylidenecyclopentene glycohybrids via palladium and click chemistry are described. Out of the six molecules synthesized, four molecules were screened against α-glucosidase, α-amylase, and glycation reactions. The results showed that the compound 7f with a galactose appendage is a good α-glucosidase inhibitor and a potent anti-glycation agent under in vitro conditions with an IC₅₀ value of 0.075 μM and 0.022 μM, respectively. The toxicity of the compounds against normal cell lines was checked by MTT assay.     

Synthesis of optically active α-aminophosphine oxides and enantioselective membrane transport of acids with their participation

Russian Journal of General Chemistry -