The chemistry of heterocyclic compounds is one of the most important areas of organic chemistry. Such structures include 5H-thiazolo[3,2-a]pyrimidine derivatives. However, few methods of modification of such derivatives are known in the literature. This is due to the fact that all chemical properties are based either on interaction with sufficiently strong nucleophilic reagents (CH-acids and cyclic disulfides) or on hydrolytic instability under acidic conditions. Furthermore, there is no information on reactivity with O-nucleophiles.

Therefore, microwave irradiation was applied as one of the effective alternative activation method. The significant reduction in reaction time and higher yields of products made this alternative heating source an attractive tool in organic synthesis. It became possible to carry out the methanolysis reaction of 2-arylmethylidentiazolo[3,2-a]pyrimidine derivatives leading to the previously unknown 2,3-disubstituted 2,3-dihydrothiazolo[3,2-a]pyrimidine derivatives in almost quantitative yields.

The investigation revealed that a single pair of stereoisomers is formed during the reaction. The formation of S-, R-, R- and R-, S-, S- isomers with trans-orientation between substituents at asymmetric carbon atoms was observed. It was thus demonstrated that the reaction proceeded diastereoselectively. Additionally, it was observed that the reaction of 2-arylmethylidentiazolo[3,2-a]pyrimidine derivatives with aqueous methanol in the presence of pyridine for 12 hours resulted in the formation of hydrolysis products, namely 3,5-diaryl-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-2-carboxylic acids, in good yields.

Thus, this work is devoted to the selective synthesis of 2,3-disubstituted-2,3-dihydrothiazolo[3,2-a]pyrimidine derivatives and the study of their structure. The obtained derivatives were characterized by a complex of physicochemical methods.

Epoxidation of alkenes is an important process in both industry and academia because epoxides are versatile intermediates in organic synthesis and they are widely used as monomers to prepare functional polymers. The presence of strained, volumetric fragments in the structure of the initial monomers makes it possible to obtain polymers with increased strength and heat resistance. Therefore, the synthesis of new compounds containing saturated three-membered oxygen-containing heterocycles is an important and urgent task of modern organic chemistry.

In this work, we carried out the epoxidation of hexacyclic dimers of norbornadiene − exo-exo-, exo-endo-, endo-exo-, endo-endo-hexacyclo[9.2.1.0^2,10.0^3,8.0^4,6.0^5,9]tetradec-12-ene under the influence of Mo-, V-, W-containing catalysts. The following oxidizing agents were tested: 4-methoxy-, 4-ethoxy-, pentafluoro-, 3-chloroperbenzoic acids, and as studies have shown, pentafluoro- and 3-chloroperbenzoic acids are the most effective. The reactions were carried out in chloroform under conditions of thermal (40-120 °C) and microwave irradiation (0.5-1 kW, 40-60 °C). It was found that when conducting experiments at room temperature for 8−48 hours, the conversion does not exceed 15%. The maximum yields (64−78%) are observed when carrying out reactions under conditions: 100 ℃, 8−12 hours, in a sealed ampoule placed in stainless steel autoclave. Interesting results were obtained when conducting experiments under microwave irradiation conditions. The maximum yields (92-96%) of the target products were observed when conducting experiments under the following conditions: 1 kW, 40 °C, 30 min. As a result of the reaction, previously undescribed 12,13-epoxyhexacyclotetradecanes are formed, the structure of which was proven by one- and two-dimensional NMR spectroscopy.

Nitrogen heterocycles are present in natural products and synthetic drugs, and represent some of the most important synthetic targets due to their numerous and valuable applications in several fields, in particular bis-heterocyclic compounds containing imidazo[1,2-a]pyridines (IMPs) are privileged heterocyclic drug scaffolds due to their potential applications.

The isocyanide based multicomponent reactions (I-MCR) are greener alternative and one of the most efficient synthetic strategies to synthesize IMPs, for example the Groebke-Blackburn-Bienaymé reaction (GBBR) allow the synthesis one pot of imidazo[1,2-a]pyridines.

On the other hand 1,2,3-triazole scaffolds are biososteres of the trans amide bond and they are of great interest in the design of novel privileged heterocycles with potential applications in medicinal chemistry, its incorporation in bioactive molecules provides advantages such as resistance to cleavage mediated by proteases and improved stability, in this context the CuAAC reaction is the most efficient approach to synthesize 1,4-disustituted-1,2,3-triazoles. The use of alternative energy source such as microwave irradiation play a key role in multicomponent reaction allowing an efficient temperature increase by the effect of dielectric heating allowing decrease of reaction time with better yields.

Herein we described a novel methodology one pot synthesis of IMPs by the GBBR-CuAAC strategy assisted by microwave irradiation.

Urea is the final product of protein breakdown in the human body and plays an important role in clinical studies for early detection of chronic conditions. The concentration of urea in the urine of a healthy individual ranges from 110 to 390 mM. The aim of this project is to develop a biosensor that can rapidly monitor urea levels using a composite of urease immobilized on bovine serum albumin (BSA), safranin (SAF), and fullerene. The receptor element of the biosensor was created by modifying a graphite-paste working electrode with a nanomaterial suspension containing fullerene, a redox-active copolymer derived from BSA and SAF, and urease enzyme. This biosensor consists of a bionanocomposite-modified working electrode, a silver chloride reference electrode, and a potentiostat providing a constant potential of +0.275 V relative to the reference electrode. Analytical signals are generated by changes in current caused by urea addition to the cell. Urea is hydrolyzed by an enzyme, and the formed ammonia interacts with a SAF. When a potential is applied, the SAF transfers electrons to an electrode, leading to a change in the current. The pH of the buffer solution must be 6.8 for accurate measurements. The range of urea concentrations that can be determined using the developed electrode is between 68 and 410 mM. This test system can be used to monitor urea concentration in urine.

The research was supported by a grant from the Russian Science Foundation No. 23-73-01220, https://rscf.ru/project/23-73-01220/

Aliphatic polyesters are an attractive class of biologically based polymers [1]. However, the thermal and mechanical properties, as well as the service life of products based on polysebacates, as with other saturated polyesters, are unsatisfactory for certain applications [2]. The introduction of modifying resins as hardeners promotes the formation of mesh polymers [3]. The scope of application of the copolymers obtained depends on the degree of crosslinking of the components and the parameters of the molecular grids, which can be adjusted during the curing process and which determine their physico-mechanical and operational characteristics [4]. An important confirmation of the formation of a spatial grid in a copolymer is its swelling value in a thermodynamically good solvent [5]. The possibility of directional variation of the crosslinking parameters of epoxy and polyester resins using a polyamide hardener has been determined. For this purpose, the influence of temperature regimes of curing, mixing technology and the ratio of the initial components have been studied. The values of the Huggins constants were initially calculated, and the use of chloroform, xylene, and dimethyformamide was investigated for this purpose. Based on the results obtained, a solvent was selected that provides optimal swelling criteria for the synthesized copolymer. Experimental data describing the swelling process of copolymer samples have been obtained. Using the Florey equation, the parameters of the structural meshes of the developed polymer compositions are calculated.

Germanium has recently gained attention as an alternative to silicon in electronics, with particular interest in dewetting processes for photonics. Dewetted surfaces, where germanium is present at 20-30%, are crucial as they enable the development of nanostructures for various applications. In this context, stable and high-coverage surface functionalization methods are essential for modulating material properties. The limited literature on germanium (Ge) functionalization does not cover SiGe systems. However, the thiol group is generally proposed as the best grafting system for these kinds of substrates. To study functionalization, we synthesized a luminescent model molecule with terminal thiol groups, easily detectable with confocal microscopy. The SiGe substrates are pre-treated with halide passivation (performed using HCl) leaving a Cl-terminated Ge. The substrates are then functionalized with the thiol-based 6-[2,7-bis[5-(5-hexyl-2-thienyl)-2-thienyl]-9-(6-sulfanylhexyl)fluoren-9-yl]hexane-1-thiol molecule. In our work, we show that this process selectively functionalizes the SiGe pattern, where germanium is present, while leaving uncovered the portion of the substrate where only silicon is present. This confirms the selective properties of the functionalization. Here, we optimized conditions for effective SiGe grafting, highlighting the crucial role of oxygen. The study shows that performing the functionalization procedure in an oxygen-free atmosphere significantly enhances the extent of coverage on the substrate, highlighting the importance of an inert environment in achieving optimal functionalization results.

Globally, fish consumption generates significant waste from fish markets and processing industries, including fish skin, scales, and bones. If not appropriately managed, this fishery waste can lead to environmental pollution. Collagen, the most abundant protein in animal bodies, has diverse medical, biomedical, and pharmaceutical applications, but its high cost has constrained its usage. Collagen derived from marine sources, particularly from byproducts of fish processing, is seen as an alternative to collagens from land animals. There has been growing interest in utilizing fish scales as a cost-effective source of this valuable collagen-rich protein. Repurposing fish scales could alleviate environmental pressure and create additional commercial value. In a recent study, collagen was isolated from the scales of Moroccan Sardina pilchardus, a fish species renowned for its high collagen content. This marine collagen type I features a triple alpha-helical structure comprising one α2 chain and two α1 chains. The collagen extraction was accomplished using the acid soluble collagen (ASC) method combined with an ultrasound technique after pretreating the fish scales, involving step demineralization to remove a high amount of minerals. The ASC extracted from the sardine scales exhibited high solubility in the highly acidic pH range (pH 2). Various physicochemical techniques such as FTIR, DRX, and MEB confirmed the isolated protein as collagen. Hence, the sardine scale could serve as an alternative source of collagen, and the characteristics of the collagens were minimally affected by the extraction process employed.

Carbon dots (CDs) are a novel class of 0-dimensional nanoparticles that belongs to the carbon-based family materials, characterized by a graphene-like core surrounded by amorphous-functionalized carbon, with dimensions under 20 nm, that have been reported for the first time in 2004 ^[1].

In recent years they have gained considerable attention due to their advantageous features, including easy bottom-up synthesis from a wide variety and low-cost starting materials, biocompatibility, low cytotoxicity, tunable photoluminescence, and photo-induced electron transfer capabilities. These properties make them highly versatile in fields such as sensing, bio-imaging, catalysis, photodynamic therapy and opto-electronic devices ^[2]. Their useful properties and applications arouse interest in the comprehension of these new materials that are eligible as the new organic counterpart of the metal-based quantum dots. However, understanding the correlation between their optical properties and nanoparticle structure remains challenging for most carbon dots.

In this contribute the photophysical properties of CDs obtained as described in literature from Citric Acid, Formic Acid and Urea were studied in two different solvents, water and DMSO and under nitrogen and oxygen atmosphere. The results indicate a possible doping effect of Oxygen which significantly impacts the optical proprieties.

[1] Xu X. et al., Journal of the American Chemical Society, (2004), 12736-12737, 126(40).

[2] Cui L. et al., Nanomaterials, (2021), 3419, 11(12).

New molecular clips, containing benzoaza-15-crown-5 moieties and diphenylglycoluril core have been synthetized. For the synthesis a previously developed method based on heating 2.1 equivalents of crown ether with one equivalent of diphenylglycoluryl bis-ether in polyphosphoric acid was used. In the case of using benzoaza-15-crown-5 derivatives, complete conversion of the reagents was observed at a higher temperature and required a longer reaction time (yields - 27-42%). Complexing properties towards to alkali and alkaline earth metal cations were evaluated through spectrophotometric titration. The clip with N-methyl groups is similar to the previously studied clip with benzo-15-crown-5 fragments, which suggests the formation of intramolecular sandwich complexes in the case of potassium and rubidium ions. However the observed stability constants are much lower - up to 3 orders of logarithmic units for potassium and rubidium. The molecular clip with unsubstituted nitrogen atoms interacts with alkali metal cations very weakly. Much stronger interactions with alkaline earth metal cations are observed. With large strontium and barium cations, very stable complexes of composition 2:1 (L:M) are formed (logK₂₁>7 for Ba²⁺). A clip with an ester group on nitrogen atoms forms the most stable complexes with the sodium ion among alkaline cations. The stability constant values ​​of this complex are an order of magnitude higher than for the other two clips, which may indicate the participation of oxygen atoms of the ester group in complex formation. In the series of alkaline earth cations, the stability of the complexes increases with increasing cation size.

During the study, a molecular system was modeled: nimesulide, β-cyclodextrin, inclusion complex. The use of the Gaussian 16 software package allowed to optimize geometry and determine the thermochemical characteristics of molecular systems without considering solvent. And also in water media, accounted for by the polarized continuum model (PCM).

To confirm the accuracy of the geometry of the β-cyclodextrin molecule, a structural alignment of 46 β-cyclodextrin molecules, accessible by a corresponding search query in the RCSB database, was performed. The RSMD values of carbon and oxygen atom deviations, as well as the total number of atoms levelled were calculated. This calculation showed a complete conformational coincidence of the designed by us β-cyclodextrin structure with the RCSB database structures. This ensures the correct approach to subsequent calculations involving this structure.

Quantum-mechanical modeling of the relationship was carried out in several stages with a gradual complexity of the basic set. Using the hybrid method of functional density B3LYP and 6-31G(d). At the end of the calculation stage, on the surface of the studied complex, the potential energy of several minimal elements is detected, This means that there are several conformational forms of the molecular system with different likely.

The change in potential energies of the investigated compounds, caused by application to optimized in vacuum molecules of the PCM model, allowed to determine values of the solvatization energies. The greater magnitude of these values in the complex under consideration indicates its better solubility in water compared to nimesulide.