Peptide Conjugates of a Nonsteroidal Anti‐Inflammatory Drug as Supramolecular Gelators: Synthesis,Characterization, and Biological Studies

Indomethacin ( IND ), which is a well‐known nonsteroidal anti‐inflammatory drug (NSAID), was conjugated with various naturally occurring amino acids. Most of these bioconjugates were capable of gelling pure water, a solution of NaCl (0.9 wt %), and phosphate‐buffered saline (pH 7.4), as well as a few organic solvents. The gels were characterized by table‐top and dynamic rheology, and electron microscopy. Variable‐temperature ¹H NMR spectroscopy studies on a selected gel were performed to gain insights into the self‐assembly process during gel formation. Both 1D and 2D hydrogen‐bonded networks were observed in the single‐crystal structures of two of the gelators. Plausible biological applications of the hydrogelators were evaluated with the ultimate aim of drug delivery in a self‐delivery fashion. All hydrogelators were stable in phosphate‐buffered saline at pH 7.4 at 37 °C, and biocompatible in mouse macrophage RAW 264.7 cell line (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay). Two of the most biocompatible hydrogelators displayed an anti‐inflammatory response comparable to that of the parent drug IND in prostaglandin E₂ assay. Release of the bioconjugates into the bulk solvent interfaced with the corresponding hydrogels indicated their plausible future application in drug delivery.     

Poly[[chlorido(1,10‐phenanthroline‐κ2N,N′)copper(II)]‐μ3‐1,1,3,3‐tetracyano‐2‐ethoxypropenido‐κ3N:N′:N′′]: coordination polymer sheets linked into bilayers by hydrogen bonds

In the title compound, [Cu(C₉H₅N₄O)Cl(C₁₂H₈N₂)]_n or [Cu(tcnoet)Cl(phen)]_n, where phen is 1,10‐phenanthroline and tcnoet is 1,1,3,3‐tetracyano‐2‐ethoxypropenide, the axially elongated (4 + 2) coordination polyhedron around the Cu^II centre contains N atoms from three different tcnoet ligands. The resulting coordination polymer takes the form of sheets which are linked in pairs by a single C—H...N hydrogen bond to form bilayers. The bond lengths provide evidence for significant bond fixation in the phen ligand and extensive electronic delocalization in the tcnoet ligand, where the two –C(CN)₂ units are rotated, in conrotatory fashion, out of the plane of the central C₃O fragment.     

Reaction of Aziridinones with 2-Lithio-1, 3-Dithiane: Selective Cleavage of the Aziridinone Ring

The reaction of aziridinones (1a-1d) with tert-butyllithium at room temperature affords α-hydroxy imines (5ax-5dx).¹ One possible pathway leading to these products involves the formation of 2 as an intermediate, followed by rearrangement to 3. In fact, under carefully controlled conditions that prevent the rearrange-of 2 to 3, α-amino ketones (4ax-4dx), which arise from the protonation of 2, can be isolated. Other α-amino ketones were synthesized in a like manner from aziridinones by treatment with a variety of alkyllithium reagents.² Baumgarten and co-workers³ subsequently reported similar products from the reaction of phenyllithium and methyllithium with an aziridinone. In an attempt to extend this study to other organolithium reagents, especially those bearing functional groups, we have investigated the reaction of     

Diastereoselective Synthesis of New Dialkylphosphorylhydrazones

A series of 22 dialkylphosphorylydrazones (dialkyl ester, N′-[(1E)-(R₁ phenyl)methylene]-phosphorohydrazidic acid), 20 of them new, along with three new N,N′-bis (diisobutylphosphorylthioamide)diamines (bis-[diisobutyl ester), N-thioxomethylene]-, diamine)phosphora-midic acid, were prepared and characterized by IR, ¹H NMR, ¹³C NMR, ³¹P NMR, and mass spectrometry. The analysis of ¹H NMR, ¹³C NMR, ³¹P NMR, and NOE spectra confirmed the observation of the single diastereoisomer E in the synthesis of dialkylphosphorylydrazones. The results of a molecular modeling study performed in order to investigate the mechanism of the synthesis of dialkylphosphorylydrazones are in agreement with the experimental results, i.e., the favored formation of diastereoisomer E over Z.     

Phosphate‐Tether‐Mediated Ring‐Closing Metathesis for the Preparation of Complex 1,3‐anti‐Diol‐Containing Subunits

An array of examples of diastereoselective, phosphate‐tether‐mediated ring‐closing metathesis reactions, which highlight the importance of product ring size and substrate stereochemical compatibility, as well as complexity, is reported. Studies focus primarily on the formation of bicyclo[n.3.1]phosphates, involving the coupling of C₂‐symmetric dienediol subunits with a variety of simple, as well as complex, alcohol partners.     

Development of a certified reference material for cachaça: an effective material for quality assurance

Cachaça is the typical and genuine denomination for the sugar cane beverage produced in Brazil. It has an alcoholic content between 38 and 48 % by volume, at 20 °C, and is obtained from the distillation of fermented sugar cane juice with the possible addition of up to 6 g/L of sugar, expressed by sucrose. This paper aims to outline the approach taken for the certification of the mass fraction of individual alcohols and their associated uncertainties in a cachaça certified reference material (CRM) produced by the Organic Analysis Laboratory of the Chemical Metrology Division of Inmetro. The requirements of ISO Guide 31, ISO Guide 34 and ISO Guide 35 were followed for the certification. This included the assessment of the degree of homogeneity of the material, the short-term stability study to determine the transport conditions, the long-term stability study to establish the shelf life and storage conditions of the CRM and the characterization process. The certified values were determined by two analytical techniques: gas chromatography coupled to mass spectrometry and gas chromatography with flame ionization detection. In order to support the routine testing of cachaça, in helping analytical laboratories validate and standardize their methods, the certified reference material (CRM 02.1/10.003b) was developed and certified for the mass fractions of methanol (9.18 mg/100 g ± 0.82 mg/100 g), 2-butanol (4.15 mg/100 g ± 0.40 mg/100 g), 1-butanol (1.30 mg/100 g ± 0.18 mg/100 g), isobutanol (24.0 mg/100 g ± 1.0 mg/100 g) and 1-propanol (29.4 mg/100 g ± 1.3 mg/100 g) in a spiked cachaça.     

Thermal decomposition study and biological characterization of zinc(II) 2-chlorobenzoate complexes with bioactive ligands

New zinc(II) 2-chlorobenzoates of general formula [Zn(2-ClC₆H₄COO)₂(L)₂] (where L = caffeine—caf, urea—u, methyl-3-pyridylcarbamate—mpc, phenazone—phen, theophylline—thp) were synthesised and characterised by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied by TG/DTG and DTA methods in nitrogen and in air atmosphere. During the thermal decomposition of the studied compounds the release of organic ligands take place followed by the decomposition of 2-chlorobenzoate anion. The volatile decomposition intermediates were proved by mass spectrometry. Zinc oxide was found as the final product of the thermal decomposition performed up to 1,000 K. The antimicrobial activity of the zinc(II) complexes against various strains of bacteria, yeasts and filamentous fungi has been investigated. It was found that the prepared compounds decreased the growth of Staphylococcus aureus, Escherichia coli, Candida albicans, Rhizopus oryzae and Microsporum gypseum, respectively. The most resistant to all tested compounds was probiotic strain of Lactobacillus plantarum. The presence of zinc and ligands in the prepared compounds increased the inhibitory effect compared to sodium salt of prepared compounds and free ligands.     

Mechanism of Framework Oxygen Exchange in Fe‐Zeolites: A Combined DFT and Mass Spectrometry Study

The role of framework oxygen atoms in N₂O decomposition [N₂O(g)→N₂(g) and 1/2O₂(g)] over Fe‐ferrierite is investigated employing a combined experimental (N₂¹⁸O decomposition in batch experiments followed by mass spectroscopy measurements) and theoretical (density functional theory calculations) approach. The occurrence of the isotope exchange indicates that framework oxygen atoms are involved in the N₂O decomposition catalyzed by Fe‐ferrierite. Our study, using an Fe‐ferrierite sample with iron exclusively present as Fe^II cations accommodated in the cationic sites, shows that the mobility of framework oxygen atoms in the temperature range: 553 to 593 K is limited to the four framework oxygen atoms of the two AlO₄^? tetrahedra forming cationic sites that accomodate Fe^II. They exchange with the Fe extra‐framework ¹⁸O atom originating from the decomposed N₂¹⁸O. We found, using DFT calculations, that O₂ molecules facilitate the oxygen exchange. However, the corresponding calculated energy barrier of 87 kcal mol^?1 is still very high and it is higher than the assumed experimental value based on the occurrence of the sluggish oxygen exchange at 553 K.     

Efficient isolation of carbonyl‐reducing enzymes using affinity approach with anticancer drug oracin as a specific ligand

Carbonyl‐reducing enzymes are important in both metabolism of endogenous substances and biotransformation of xenobiotics. Because sufficient amounts of native enzymes must be obtained to study their roles in metabolism, an efficient purification strategy is very important. Oracin (6‐[2‐(2‐hydroxyethyl)aminoethyl]‐5,11‐dioxo‐5,6‐dihydro‐11H‐indeno[1,2‐c] isoquinoline) is a prospective anticancer drug and one of the xenobiotic substrates for carbonyl‐reducing enzymes. A new purification strategy based on molecular recognition of carbonyl‐reducing enzymes with oracin as a ligand is reported here. The type of covalent bond, ligand molecules orientation, and their distance from the backbone of the solid matrix for good stearic accessibility were taken into account during the designing of the carrier. The carriers based on magnetically active microparticles were tested by recombinant enzymes AKR1C3 and CBR1. The SiMAG‐COOH magnetic microparticles with N‐alkylated oracin and BAPA as spacer arm provide required parameters: proper selectivity and specificity enabling to isolate the target enzyme in sufficient quantity, purity, and activity.     

A comparison of various modes of liquid–liquid based microextraction techniques: Determination of picric acid

Three modes of liquid–liquid based microextraction techniques – namely auxiliary solvent‐assisted dispersive liquid–liquid microextraction, auxiliary solvent‐assisted dispersive liquid–liquid microextraction with low‐solvent consumption, and ultrasound‐assisted emulsification microextraction – were compared. Picric acid was used as the model analyte. The determination is based on the reaction of picric acid with Astra Phloxine reagent to produce an ion associate easily extractable by various organic solvents, followed by spectrophotometric detection at 558 nm. Each of the compared procedures has both advantages and disadvantages. The main benefit of ultrasound‐assisted emulsification microextraction is that no hazardous chlorinated extraction solvents and no dispersive solvent are necessary. Therefore, this procedure was selected for validation. Under optimized experimental conditions (pH 3, 7 × 10^?5 mol/L of Astra Phloxine, and 100 μL of toluene), the calibration plot was linear in the range of 0.02–0.14 mg/L and the LOD was 7 μg/L of picric acid. The developed procedure was applied to the analysis of spiked water samples.