Chemistry Proceedings

We have previously obtained significant results in the cycloalumination of olefins with EtAlCl₂ in the presence of magnesium and a Cp₂ZrCl₂ or Cp₂TiCl₂ catalyst. Here we report the development of an efficient one-pot catalytic method for the synthesis of tertiary alcohols from AlCl₃, aryl olefins, and ketones under the action of Cp₂TiCl₂. The developed method for producing tertiary alcohols has a general character and allows the conversion of styrene and substituted styrenes (ortho-, para-methylstyrenes) into aryl-substituted tertiary alcohols with yields of up to 76% in the reaction with acetone or methyl ethyl ketone. We assume that the reaction proceeds through the formation of a titanacyclopropane intermediate. Full article

The preparation of enoxaparin via the base-promoted depolymerization of heparin is well known. In this paper, we present our efforts to convert this preparation into a flow method. Streams of base and ester solutions are combined and heated in a flow reactor, and the variations in flow rate, temperature, and residence time were examined. NMR analysis demonstrated that careful control of the reaction parameters affords enoxaparin-like materials. An analysis was carried out by NMR spectroscopy and the optimum conditions were determined. Full article

Lanthanide (Ln(III)) luminescent complexes have been attracting interest for technological applications and molecular imaging. The luminescence of Ln(III)) ions is weak and depends on the use of light absorbing coordination ligands which sensitizes the lanthanide ion. A large variety of coordination ligands has been screened such as dipicolinates, oligo-pyridines, cyclen and crown ether derivatives, porphyrins, cryptands or calixarenes. In our research group we have developed an expeditious methodology to prepare bis(oxazolyl)pyridine ligands for LnIII from threonine and 2,6-pyridinedicarbonyl dichloride. In this work, two new pyridine-bis-oxazolyl ligands with an aromatic ring in position 5 of the oxazole ring were prepared from phenyl-serine and 2,6-pyridinedicarbonyl dichloride. The photophysical properties of compounds 1 and 2 were studied in acetonitrile and in Tris-HCl buffer (0.1 M, pH 7.1). These compounds were used for complexation with Eu(III) and/or Tb(III) ions and the photophysical properties of the complexes studied. Luminescence titrations with anhydrous EuCl₃ and TbCl₃ allowed the determination of the stoichiometry of the complexes and of the stability constants. Full article

This work investigates the inclusion of the nimesulide molecule into the beta- and gamma- cyclodextrin cavity and explores the application of molecular modelling for the purposes of proving the host-guest complexation process. The author’s experimental method is based upon the basic methods of obtaining inclusion complexes. A combination of physical and chemical methods was utilized in order to analyze the compounds obtained qualitatively and quantitatively. In addition, it was decided that the focus will be on figuring out the possibility applying computer modeling. The characteristics of the molecular systems under study were calculated using the «Gaussian 09W» software package (Revision version 16 A.03). The functionality of this software package allowed us to apply both the restricted Hartree–Fock (RHF) method, and the hybrid density functional method-B3LYP. The 6–31 G split-valence basis set was utilized for all subsequent calculations, to quantify the influence of the additional polarization and diffuse functions on the calculations. Using computational chemistry, the structures of γ-, β-cyclodextrin, nimesulide, and surface complex compounds were constructed and optimized. The possible structures of nimesulide inclusion complexes with β-, γ-cyclodextrin were also designed. The results obtained will influence the evaluation of the possibility of obtaining the clathrate complex. The crystal structure of the nimesulide inclusion complex obtained by us with γ-cyclodextrin was experimentally confirmed by X-ray diffraction analysis. To date, not many works are known to utilize these molecular modeling techniques in the field of supramolecular chemistry based on an independently synthesized inclusion complex. Full article

The crystal structures of mononuclear cyclopalladated compounds with phosphine ligands are investigated. The reactions of the five-membered cyclopalladated dinuclear complexes [Pd(L)(µ-Cl)]₂ with the monophosphine ligand (PPh₃) and diphosphine ligand (dppm) in the molar ratio of 1:2, and ammonium hexafluoride in the case of compound b, result in the mononuclear complexes [Pd{2,3,4-(CHO)C₆H₃C(H)=NCy}{PPh₃}[Cl] (1a) and [Pd{2,3,4-(CHO)C₆H₃C(H)=NCy}{Ph₂PCH₂PPh₂-P,P}][PF6] (1b). Full article

The infectious agent Mycobacterium tuberculosis (MTB) has several defense and resistance mechanisms that must be eliminated. The treatment is prolonged, which in many cases generates susceptibility to microbial resistance. This research aimed to study whether the antimicrobial peptide Ctx(Ile²¹)-Ha-Ahx-Cys (Ctx-SH) functionalized in nanochitosan matrices could eliminate resistant MTB. For this, a nanosystem was developed with chitosan matrices previously modified with N-acetylcysteine functionalized to Ctx-SH. Modified chitosan nanoparticles (NPQ) were obtained by ionic gelation using sodium tripolyphosphate and loaded with rifampicin. Both chitosan and NPQ modifications were analyzed for physicochemical parameters by Fourier/Raman transform infrared spectroscopy and Zeta potential. Antimicrobial activity was performed in a level 3 biosafety laboratory with strains H37Rv (standard) and CF169 (extensively drug-resistant, XDR) incubated in 7H9 broth supplemented with oleic acid, albumin, dextrose, and catalase at 37 °C and 5% CO₂ and read using fluorescence with 0.01% resazurin after 7 days. Insertion and mapping of NPQ into macrophages were assessed using a confocal microscope after 24 h with NPQ conjugated to fluorescein isothiocyanate. Preliminary results show that the spectroscopies corroborate the hypothesis of the functionalization of the Ctx-SH peptide to the chitosan-N-acetylcysteine system because, when comparing the three spectroscopies, a gradual increase in the intensity of several bands and the formation of captive disulfide are observed, and the Zeta potential (+30 mV) confirmed high application stability. Bacterial inhibition studies revealed that rifampicin-loaded antimicrobial peptide-conjugated chitosan nanoparticles have better activity than rifampicin alone against CF169, with a minimum inhibitory concentration of <0.977 µg/mL, similar to the standard strain. In addition, it was shown that NPQ would be able to enter the macrophage without causing toxicity and thus take better advantage of the activity of rifampicin. Finally, it is possible to verify that the nanobioconjugation of the Ctx-SH-N-acetylcysteine-chitosan compound is capable of enhancing the activity of obsolete drugs and/or sensitizing XDR bacteria. Full article

Graphitic carbon nitride-supported L-arginine (g-C₃N₄@L-arginine) has been prepared as a heterogeneous catalyst for synthesizing heterocyclic compounds such as pyranopyrazole and acridinedione derivatives. High efficiency, short reaction time, and easy separation are significant features that are reasons for using g-C₃N₄@L-arginine as a catalyst in one-pot multicomponent reactions. Synthesized nanocatalyst was detected by numerous analyses, such as FE-SEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive X-ray spectroscopy), XRD (X-Ray Diffraction analysis), TGA (Thermo Gravimetric Analysis), and FT-IR (Fourier Transform Infrared Spectroscopy). G-C₃N₄@L-arginine nanocatalyst was reused 5 times in the reaction with no apparent decrease in reaction yield, which shows acceptable recyclability. Full article

Organophosphorus compounds have been investigated for agricultural and medicinal applications for decades, and a considerable number of phosphorus-containing drugs have achieved commercial success. A recent review by P. Finkbeiner et al. has shown that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist’s toolbox. A new approach to the synthesis of previously hard-to-obtain 3-alkyl-1H-phospholanes oxides was developed by us. In order to assess the potential of five-membered cyclic organophosphorus compounds in cancer therapy, we carried out docking 3-buthyl-1H-phospholanes oxide and 2,3-dihydrophosphole in the binding site of 24 human proteins involved in oncogenesis processes. Proteins were selected using the PharmMapper in-house pharmacophore model database. The results are presented in the article. Full article

Schiff bases have been important compounds ever since their discovery and are both found in nature and synthesized in the laboratory. They participate in a variety of synthetic processes and possess desirable biological activity, including antibacterial, anti-inflammatory, antioxidant, and anticancer activity, among others. In this study, eight Schiff bases derived from the reaction of 4-aminoantipyrine with various cinnamaldehydes have been synthesized and characterized. All derivatives were tested in vitro on several human carcinoma cell lines to determine their antitumor activity and against different bacteria strains of clinical and food industry importance to evaluate their antibacterial activity. Several of the Schiff bases evaluated inhibited tumor cell growth in a dose-dependent manner. The compound that exhibited the most activity against all cell lines had IC₅₀ values of less than 18 μM. On the other hand, during the evaluation of the antibacterial activity, only two Schiff base derivatives showed interesting antibacterial effects, with MIC values under 250 μM. These two Schiff base derivatives mainly exhibited a bacteriostatic effect against most of the studied bacterial strains. It is interesting to note that the same Schiff base presents the best activity in both biological evaluations. Full article

Recently, a series of thirty-eight 4-{[(benzyloxy)carbonyl]amino}-2-hydroxybenzoic acid amides designed as potential acetyl- and butyrylcholinesterase (AChE/BChE) inhibitors were described as potential drugs to alleviate the symptoms of Alzheimer’s disease (AD). Some of these compounds have shown promise for inhibiting either AChE or BChE. Since these compounds are structurally similar to agents inhibiting beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), the aim of the contribution was to verify how our compounds were able to affect this enzyme, which, when inhibited, blocks the formation of amyloid-β, but whose inhibition is associated with significant adverse effects in humans. At a concentration of 10 µM, only benzyl {4-[(4-fluorophenyl)carbamoyl]-3-hydroxyphenyl}carbamate was found to show approximately 28% inhibition of BACE1 activity. Full article

A transnational concern for the healthy development of human beings is antimicrobial resistance (AMR). The rising rates of microbial resistance present a serious issue for the development of human life and hence it is essential to find and create newer antimicrobial drugs with unique modes of action. One approach used these days to solving this challenge is the use of heterocyclics to create hybrid compounds by fusing two or more bioactive heterocyclic moieties into a single molecular platform. This study discusses the many hybrid approaches that have been used to produce possible novel antimicrobial medicines that are both safe and effective. The landscaping of heterocycles such as thiazole derivatives is covered in the current review paper. In this paper, all the extensive approaches of heterocyclic composites, primarily thiazole derivatives, exhibit vibrant biological activity. The purpose of this work is to support methods that may be used to create various thiazole derivatives and their biological activity. This paper will offer great recommendations for potential medicine designs in the future. Full article

Recently, multi-component, one-pot reactions have been shown to be efficient and environmentally friendly methods compared to traditional, linear-step syntheses. Heterogeneous catalyzed multicomponent reactions are one of the green approaches to the synthesis of organic compounds, especially pyrazoles and their derivatives. Here we demonstrate the one-pot synthesis of pyrazoles using heterogeneous nickel-based catalysts for the condensation of various hydrazine, ketone derivatives, and aldehyde derivatives at room temperature. The thus synthesized heterogeneous catalyst can be reused up to the seventh cycle without much loss of catalytic activity. Full article

This communication reports the synthesis of a series of bis (1,4-disubstituted-1,2,3-triazoles) starting from the known (2,3,4,5) bis acetonide-protected diethyl galactarate (1). Reduction of 1 with LiAlH₄ led to dioxolane 2 (90%), which, upon treatment with CBr₄, gave the corresponding dibromide 3 (80%). The reaction of 3 with NaN₃ in DMF afforded the key diazide 4 (95%). From the diazide 4 were obtained the bis (1,4-disubstituted-1,2,3 triazoles) 5–8 via click reactions with alkyl-substituted acetylenes, including triphenyltinacetylene. The physical characteristics of the new compounds, including selected values of ¹H, ¹³C, and ¹¹⁹Sn NMR data, are given. Full article

The blooming ethnomedicinal plant Uvaria narum (Dunal) Wall is mostly found in the deep forests of the Western Ghats and belongs to the Annonaceae family. Uvaria narum is a spreading, pubescent shrub with large, dark bluish-green leaves. Phytochemistry and pharmacognostic studies have revealed that the plant possesses a variety of phytochemicals that are remarkable and beneficial to humans. The plant also possesses a number of beneficial properties, such as antioxidant activity exhibited by the presence of polyphenols and tannins, antifungal activity brought on by the benzoic acid moiety, and tumour-fighting ability contributed by terpenoid and alkaloids. The presence of phytoconstituents in the plant has been attributed to the various medicinal properties of the plant, such as anticancer activity. The plant may also be considered for use against ageing and other diseases caused by free radicals. In vitro cytotoxicity is due to terpenoids, phytosterols, and flavonoids, whereas the liver is protected by flavonoids. The chemical profile of the plant shows that acetogenins, including stereoisomers, are important constituents of the root bark. Eczema, itching, varicose veins, haemorrhoids, jaundice, inflammation, and fever are the main ailments for which this herb is used. Full article

An example of a new BODIPY design with triplet state population is reported: BINOL-O-BODIPY-based dimer. This new design combines two easily accessible structural features with a demonstrated capability of populating triplet states without the need for iodine or heavy metals: meso-p-phenylene-bridged BODIPY dimer and BINOL-O-BODIPY. Full article

Two gold(I) complexes have been synthesized by a two-step reaction. The first reaction step was the deprotonation with butyllithium to obtain the corresponding NHC. In the second reaction step, the metal precursor was added to afford the corresponding gold complex. At this point, the complex obtained depends on the nature of the metal precursor. A monocarbene complex (sydnone-Au-tht) was obtained using [Au(tht)Cl] as the metal precursor and a biscarbene complex (sydnone-Au-imidazolium) was obtained using a gold imidazolium complex as the metal precursor instead. The ¹³C-NMR resonance frequencies of the carbene carbon atom shifted to higher values from 97.3 to 135.6–139.7 ppm, mono and biscarbene, respectively. Full article

The outbreak of SARS-CoV-2 created the biggest crisis to human health and has adversely affected economic growth worldwide. Several vaccines emerged from manufacturers to combat COVID-19. Unfortunately, no therapeutic medication has yet been approved by the FDA for the treatment of this disease. Many researchers have performed in silico studies for the identification of potential SARS-CoV-2 inhibitors from the molecules present in Indian medicinal plants and spices. In this paper, we have performed a structure-based virtual screening (VS) of 120 compounds derived from Nigella sativa (NS) against M^pro, PL^pro, and spike proteins of SARS-CoV-2. Strong binding interactions of M^pro occurred with hits NS-40 and NS-84, whereas hits NS-72D and NS-95D showed strong binding interactions with spike proteins. Interestingly, four promising hits (i.e., NS-21, NS-40, carvacrol (NS_08), and menthol) exhibited good binding interactions with both M^pro and spike proteins. Carvacrol, a monoterpenoid phenol possessing several biological activities, showed a favourable binding affinity towards the papain-like protease of SARS-CoV-2. This small molecule may be used as a natural weapon to combat COVID-19. Full article

The ubiquitous presence of sp³ C−H bonds in natural feedstock makes them inexpensive, easily accessible, and attractive synthons for the preparation of common and/or complex molecular frameworks in biologically active natural products, pharmaceutics, agrochemicals, and materials. However, the inertness of these bonds due to the high bond dissociation energies and low polarity difference between the carbon and hydrogen atoms makes them challenging reaction partners. Moreover, the desired site-selectivity is often an issue in reactions with multiple analogous sp³ C−H bonds. To overcome these problems, transition metal-catalyzed C−H functionalization has been developed with the assistance of various well-designed directing groups which can coordinate to a metal center to deliver it on a targeted C−H bond through an appropriate spatial arrangement, enabling C−H activation via the formation of a cyclometalated species. However, the frequent requirement of additional steps for the construction of the directing groups and their subsequent removal after the desired operation severely hampers the efficacy and compatibility of the reactions. A promising solution would be the utilization of a transient ligand which can bind to the substrate and coordinate to the metal center in a reversible fashion. In this way, the directing group is installed, sp³ C−H functionalization occurs, and the directing group is then removed in situ without affecting the substrate function after the catalysis is finished. Overall, the whole process occurs in a single reaction pot. Herein, we are presenting our studies on transition metal-catalyzed transient directing group-enabled C−H functionalization reaction. Full article

This study examined the rheological properties of alginates, one of the main products obtained from algae. These polysaccharides are widely used in fields such as pharmaceuticals, medical technology, cosmetics, food, agriculture and the textile and paper industries. Therefore, sodium alginate was obtained from waterweed (Charophyceae) in the following experiment. The structure and composition of the sodium alginate were analyzed using physical and chemical research methods: IR spectroscopy and XRD. Full article