Antimicrobial Polymers Prepared by Ring‐Opening Metathesis Polymerization: Manipulating Antimicrobial Properties by Organic Counterion and Charge Density Variation

The synthesis and characterization of a series of poly(oxanorbornene)‐based synthetic mimics of antimicrobial peptides (SMAMPs) is presented. In the first part, the effect of different organic counterions on the antimicrobial properties of the SMAMPs was investigated. Unexpectedly, adding hydrophobicity by complete anion exchange did not increase the SMAMPs’ antimicrobial activity. It was found by dye‐leakage studies that this was due to the loss of membrane activity of these polymers caused by the formation of tight ion pairs between the organic counterions and the polymer backbone. In the second part, the effect of molecular charge density on the biological properties of a SMAMP was investigated. The results suggest that, above a certain charge threshold, neither minimum inhibitory concentration (MIC₉₀) nor hemolytic activity (HC₅₀) is greatly affected by adding more cationic groups to the molecule. A SMAMP with an MIC₉₀ of 4 μg mL^?1 against Staphylococcus aureus and a selectivity (=HC₅₀/MIC₉₀) of 650 was discovered, the most selective SMAMP to date.     

Synthesis of novel macrocyclic crown ethers from D-glucose

A simple and efficient synthetic protocol for an easy access of carbohydrate-linked crown ethers from cheap and readily available D-glucose in good yields has been devised. The base-mediated cyclization of sugar-linked bis-iodo podands in CH₃CN with amines, including ethylamine and furfurylamine afforded the novel chiral monoaza-15-crown-5-type macrocyclic crown ethers anellated to 3-O-benzyl-1,2-O-isopropylidene-α-D-glucofuranose and 3-O-benzyl-1,2-O-isopropylidene-α-D-allofuranose. The glucose-based crown ethers have been characterized by spectroscopy techniques including IR, ¹H NMR, and ¹³C NMR.     

Deciphering the Potential of Pre and Pro-Vitamin D of Mushrooms against Mpro and PLpro Proteases of COVID-19: An In Silico Approach

Vitamin D’s role in combating the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the virus causing COVID-19, has been established in unveiling viable inhibitors of COVID-19. The current study investigated the role of pre and pro-vitamin D bioactives from edible mushrooms against Mpro and PLpro proteases of SARS-CoV-2 by computational experiments. The bioactives of mushrooms, specifically ergosterol (provitamin D₂), 7-dehydrocholesterol (provitamin-D₃), 22,23-dihydroergocalciferol (provitamin-D₄), cholecalciferol (vitamin-D₃), and ergocalciferol (vitamin D₂) were screened against Mpro and PLpro. Molecular docking analyses of the generated bioactive protease complexes unravelled the differential docking energies, which ranged from −7.5 kcal/mol to −4.5 kcal/mol. Ergosterol exhibited the lowest binding energy (−7.5 kcal/mol) against Mpro and PLpro (−5.9 kcal/mol). The Molecular Mechanics Poisson–Boltzmann Surface Area (MMPBSA) and MD simulation analyses indicated that the generated complexes were stable, thus affirming the putative binding of the bioactives to viral proteases. Considering the pivotal role of vitamin D bioactives, their direct interactions against SARS-CoV-2 proteases highlight the promising role of bioactives present in mushrooms as potent nutraceuticals against COVID-19.     

Hetero-Diels–Alder reaction of aromatic aldehydes catalyzed by titanium tetrachloride: computational and experimental results

Computational calculations of the hetero-Diels–Alder (HDA) reactions of benzaldehyde with 2,3-dimethyl-1,3-butadiene (DMB) catalyzed by BF₃, EtAlCl₂ or TiCl₄ at the density functional theory (DFT) (B3LYP/6-31G(d,p)) level reveal that the reactions involve activation energy barriers of 14.59, 14.34, and 17.44 kcal mol⁻¹, respectively. In the first two cases, reaction occurs through a concerted mechanism, whereas in the presence of TiCl₄, stepwise mechanism involving zwitterionic intermediate is followed. The reaction with isoprene proceeds with complete regioselectivity leading to the expected regioisomer having O/Me in 1:4 positions. The computational results have been verified experimentally when aromatic aldehydes react with 1,3-dienes in the presence of a catalyst to give 3,6-dihydro-2H-pyran derivatives in high yields.     

Magnetic, electronic and electrochemical studies of mono and binuclear Cu(II) complexes using novel macrocyclic ligands

A series of new mono and binuclear copper (II) complexes [Cul]X(2)and [Cu(2)lX(2)] where 1 = L(1), L(2) and L(3) are the macrocyclic ligands. In mononuclear complexes the geometry of Cu(II) ion is distorted squareplanar and in binuclear complexes the geometry of Cu(II) is tetragonal. The synthesized complexes were characterized by spectroscopic (IR,UV-vis and ESR) techniques. Electrochemical studies of the complexes reveals that all the mononuclear Cu(II) complexes show a single quasireversible one-electron transfer reduction wave (E(pc) = -0.76 to -0.84V) and the binuclear complexes show two quasireversible one electron transfer reduction waves (E(pc)(1) = -0.86 to -1.01V, E(pc)(2) = -1.11 to -1.43V) in cathodic region. The ESR spectra of mononuclear complexes show four lines with nuclear hyperfine splittings with the observed g(11) values in the ranges 2.20-2.28, g( perpendicular) = 2.01-2.06 and A(11) = 125-273. The binuclear complexes show a broad ESR spectra with g = 2.10-2.11. The room temperature magnetic moment values for the mononuclear complexes are in the range [mu(eff) = 1.70-1.72BM] and for the binuclear complexes the range is [mu(eff) = 1.46-1.59BM].     

Determination of nitrate in environmental water samples by conversion into nitrophenols and solid phase extraction−spectrophotometry, liquid chromatography or gas chromatography-mass spectrometry

Conversion of nitrate into a nitro-phenol derivative by reaction with 2-methylphenol or 2,6-dimethylphenol allowed at least 100-fold enrichment of the derivative on Lichrolut EN polymeric cartridge, and it is stable for up to 1 month on the cartridge. The derivative could be eluted with ammonia-methanol mixture. This reaction for nitrate determination has permitted a choice of final measurement by UV-Vis spectrophotometry, liquid chromatography or gas chromatography-mass spectrometry when the limits of detection were 10, 6 and 3 μg l⁻¹, respectively, and the calibration range 20 μg to 10 mg l⁻¹ nitrate. The method has been validated by spiking natural water samples, when the recovery of nitrate was 98.5-108.4% (relative standard deviation 2.5-6.1%).     

Facile and highly selective conversion of nitriles to amides via indirect acid-catalyzed hydration using TFA or AcOH-H2SO4

Both aliphatic and aromatic nitriles are conveniently and selectively converted in a single step, via an indirect acid-catalyzed hydration, into the corresponding amides in 1-8 h using a TFA-H2SO4 mixture as a reagent system. Although the same reagent did not work for the sterically hindered nitriles such as mesitonitrile, the transformation could be accomplished by changing TFA to AcOH at higher temperatures (>90 degrees C).     

Sucrose chelated auto combustion synthesis of BiFeO3 nanoparticles: Magnetically recoverable catalyst for the one‐pot synthesis of polyhydroquinoline

Sucrose chelated Bismuth ferrite (BiFeO₃) nanoparticles as a novel heterogeneous catalyst was synthesized by an auto combustion route. Different calcination temperatures (150 °C, 450 °C, 550 °C, 650 °C, 750 °C and 850 °C) have been employed to obtain single phased BiFeO₃ nanoparticles. The perovskite structure formation and disappearance of organic phase (sucrose) was obtained by Fourier transform infrared spectroscopy (FT‐IR). Phase determination and structural characterization was carried out by powder X‐ray diffraction (XRD). The magnetic properties were analyzed by vibrating sample magnetometer (VSM) whereas surface area/pore volume was obtained by Brunauer–Emmett–Teller (BET). Transmission electron microscope (TEM) analyzed the particles size and morphology. Thermal stability was investigated by thermogravimetric analysis (TGA) and determination of constituent elements was carried out by X‐ray Photo‐Electron Spectroscopy (XPS). Raman spectroscopy confirmed the perovskite structure of the synthesized materials. The BiFeO₃ nanoparticles so obtained were employed as heterogeneous catalyst for the synthesis of polyhydroquinoline derivatives. All the polyhydroquinoline derivatives were characterized by Fourier transform infrared spectroscopy (FT‐IR) and Nuclear magnetic resonance spectroscopy (¹H NMR). For the very first time ever we have used BiFeO₃ as a recyclable magnetic nanocatalyst in the one‐pot four component cyclization reaction of benzaldehyde, ethylacetoacetate/methylacetoacetate, dimedone/cyclohexane‐1,3‐dione, and ammonium acetate for the synthesis of polyhydroquinoline derivatives without solvent under refluxing conditions to provide excellent yields of products. BiFeO₃ nanocatalyst (without any functionalization/surface coatings) shows easy magnetic separation, recyclability, reusability along with excellent yield of polyhydroquinoline derivatives in an economic and benign way.     

Effect of zinc chloride on structural, optical and dielectric behavior of solution grown anthracene crystal

Pure and ZnCl₂ doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 °C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.