Non-natural nucleosides based on 1,2,4-triazolo[5,1-c][1,2,4]triazin-4(6H)- ones

Two regioselective methods for the synthesis of nucleosides in the series of 3-phenyl- and 3- ethoxycarbonyl-1,2,4-triazolo[5,1-c][1,2,4]triazin-4-ones were developed. The first route involves a Vorbrüggen glycosylation reaction. The second one is based on condensation of 1,2,4- triazolo[5,1-c][1,2, 4]triazin-4-one sodium salts with protected 1-bromo-sugar derivatives

Synthesis of acyclic nucleoside analogues by one-step Vorbrüggen glyco-sylation of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones

New analogues of acyclovir have been prepared by reacting 1,2,4 -triazolo[1,5-a]pyrimidin-7-ones 1а-i and (2-acetoxyethoxy)methyl acetate 2 in the presence of trimethylsilyl trifluoromethanesulfonate as a catalyst. The interaction between the compounds 1а-е and 2 has led to a mixture of N3 and N4 isomers. In contrast, the reaction of compounds 1g-i and 2 proceeded selectively to form N3 isomers. In the case of compounds 1a-c the predominant product is the one with the acyclic moiety in azine ring (N4 isomer). Interaction between 1d-f and 2 has led to mixtures comprising mainly N3 isomer. It has been found that the ratio of glycosylation products 1 and 2 are thermodynamically controlled. The structure of the obtained compounds has been proved by 1Н, 13С, two-dimensional 1Н-13С NMR spectroscopy and X-ray analysis

Investigation of Structure, Chemical and Phase Composition of Silicon Spring Steel Scale

The article presents the results of investigation of structure, chemical and phase composition of scale formed on siliceous spring steels during high-temperature heating prior to rolling. It is established that in 40S2 steel, the hematite layer bordering furnace atmosphere has a minimum thickness of about 40–60 μm, the magnetite layer has thickness of 250 ± 280 μm, the largest thickness of 800 ± 900 μm has wustite layer with secondary ferriferous oxide released during cooling, bordering the steel surface. The scale layer adjacent to the steel surface is characterized by a much greater macrostructural, chemical, and phase inhomogeneity. In addition towustite–ferriferous oxide mixture, iron silicates with an increased silicon content are present. Approaching the steel surface, the number of zones enriched with silicon increases. When 60S2ChA steel is heated to 1180–1200∘С, zones enriched with silicon are observed in the scale at a distance of 200 ± 250 μm from the metal surface, and when heated to temperatures of 1310 ± 1315∘C at a much larger distance, reaching700–800 μm. Keywords: scale, steel heating, siliceous springs steel, scale microstructur

Long-range 1H-15N J couplings providing a method for direct studies of the structure and azide-tetrazole equilibrium in a series of azido-1,2,4-triazines and azidopyrimidines

The selectively 15N labeled azido-1,2,4-triazine 2*A and azidopyrimidine 4*A were synthesized by treating hydrazinoazines with 15N-labeled nitrous acid. The synthesized compounds were studied by 1H, 13C, and 15N NMR spectroscopy in DMSO, TFA, and DMSO/TFA solutions, where the azide-tetrazole equilibrium could lead to the formation of two tetrazoles (T, T′) and one azide (A) isomer for each compound. The incorporation of the 15N label led to the appearance of long-range 1H-15N coupling constants (JHN), which can be measured easily by using amplitude-modulated 1D 1H spin-echo experiments with selective inversion of the 15N nuclei. The observed JHN patterns enable the unambiguous determination of the mode of fusion between the azole and azine rings in the two groups of tetrazole isomers (2*T′, 4*T′ and 2*T, 4*T), even for minor isoforms with a low concentration in solution. However, the azide isomers (2*A and 4*A) are characterized by the absence of detectable J HN coupling. The analysis of the JHN couplings in 15N-labeled compounds provides a simple and efficient method for direct NMR studies of the azide-tetrazole equilibrium in solution. © 2013 American Chemical Society

Spin-spin coupling constants 13C-15N and 1H-15N in the investigation of azido-tetrazole tautomerism in a series of 2-azidopyrimidines

A new method was developed for the investigation of an azido-tetrazole equilibrium based on using a complex analysis of 13C-15N and 1H-15N spin-spin coupling constants. The use of this approach became possible due to the selective inclusion of 15N isotopes into the structures of 2-azidopyrimidines and their cyclic analogs tetrazolo[1,5-a]pyrimidines. © 2013 Springer Science+Business Media New York

Influence of various parameters on the vegetable raw material pelleting process and pellets quality (review)

Determining the regularities of the process of pelleting vegetable raw materials is relevant for the improvement of technologies and technical equipment in order to reduce energy intensity and improve the quality of pellets. The generalization of the results of the research aimed at studying the influence of various parameters on the process of pelleting vegetable raw materials and the quality of feed and biofuel pellets is the purpose of the research. A selection and systematic review of the scientific literature on the subject of the study for the period of 2007-2022 has been carried out. The analysis has proved that heat pre-treatment and moistening of vegetable raw materials, as well as their composition and particle size are the factors that have the greatest impact on the quality of feed and biofuel pellets. Increasing the pressure in the range of 20...200 MPa results in increasing the pellets durability. A die temperature of around 100°C is optimum for obtaining dense pellets of highquality from vegetable raw materials. The design parameters of the pelletizer play an important role in obtaining high-quality pellets when processing vegetable raw materials. The design of the inlet in the form of a tapering cone helps to reduce energy consumption and pelleting pressure. An increase in the ratio of the die channel length to its diameter exponentially increases the pelleting pressure and its energy intensity. The interplay between the physical processes occurring in the pelletizer makes it difficult to interpret the impact of each parameter on the pelleting process, so different authors have different assessments of the contribution of individual factors in producing high-quality pellets. Therefore, the interaction between the individual pelleting parameters and their influence on the results of the process should be examined more precisely

Incorporation o f stable isotopes 2H, 13C and 15N in the structure of azolo[5,1-c][l,2,4]triazines and azolo[1,5-a]pyrimidine as a tool for studying the chemical and biological transformations of nitrogenous heterocycles

It is shown that selective incorporation of stable isotopes allows one to expand standard capabilities of NMR spectroscopy and is an effective approach to the study of the structure and reactivity of organic compounds. Azidotetrazole equilibrium, Dimroth rearrangement, and adamantylation of azoloazines were examined using compounds labeled by stable isotopes.This work was financially supported by the Ministry o f Education and Science o f the Russian Federation (state contract in 2458)

The Foundations of the Development of Technologies of the Synthesis of Radiopharmaceuticals

The selection of precursors (for example chelating agents) and development of a technique of chemical modification of the target molecules retaining its ability to bind to specific receptors are very important in the synthesis of radiopharmaceuticals. As some important precursors for target radiopharmaceuticals omega-iodo-aliphatic carboxylic acids and their esters can be used. We have developed an environmentally safe process for producing omega-iodoaliphatic carboxylic acids and their esters of the available, inexpensive and low toxic aliphatic cyclic ketones. We proposed a new method for the synthesis of the chelating agents omega-thia- or (bis(2-hydroxyethyl)amino)- aliphatic carboxylic acids (chelate 1 and chelate 2), which was caused by the existing disadvantages in the existing methods. Thus, based on our method the precursors (chelates) with yield of over 70-90% on the final stage were synthesized, and then the high effectiveness in producing target radiopharmaceuticals using different biomolecules was showed. 99mTc-chelates complexes were prepared with radiochemical purity >91% and found to be stable at room temperature for six hours