Cytokinins, classical phytohormones, affect all stages of plant ontogenesis, but their application in agriculture is limited because of the lack of appropriate ligands, including those specific for individual cytokinin receptors. In this work, a series of chiral N⁶-benzyladenine derivatives were studied as potential cytokinins or anticytokinins. All compounds contained a methyl group at the α-carbon atom of the benzyl moiety, making them R- or S-enantiomers. Four pairs of chiral nucleobases and corresponding ribonucleosides containing various substituents at the C2 position of adenine heterocycle were synthesized. A nucleophilic substitution reaction by secondary optically active amines was used. A strong influence of the chirality of studied compounds on their interaction with individual cytokinin receptors of Arabidopsis thaliana was uncovered in in vivo and in vitro assays. The AHK2 and CRE1/AHK4 receptors were shown to have low affinity for the studied S-nucleobases while the AHK3 receptor exhibited significant affinity for most of them. Thereby, three synthetic AHK3-specific cytokinins were discovered: N⁶-((S)-α-methylbenzyl)adenine (S-MBA), 2-fluoro,N⁶-((S)-α-methylbenzyl)adenine (S-FMBA) and 2-chloro,N⁶-((S)-α-methylbenzyl)adenine (S-CMBA). Interaction patterns between individual receptors and specific enantiomers were rationalized by structure analysis and molecular docking. Two other S-enantiomers (N⁶-((S)-α-methylbenzyl)adenosine, 2-amino,N⁶-((S)-α-methylbenzyl)adenosine) were found to exhibit receptor-specific and chirality-dependent anticytokinin properties.

Coronaviruses (CoVs) belong to a large family of zoonotic supercapsid viruses, including about 40 species of RNA-containing viruses with several strains capable of causing damage to the lungs and respiratory tract. The severe acute respiratory syndrome coronavirus (SARS-CoV) was responsible for the worldwide SARS outbreak in 2003. The rapid global spread of SARS-CoV-2 has been the cause of significant health concerns and thousands of deaths in 2019-2020 and outlined the need for novel antivirals. The present review is devoted to the development of effective and selective nucleoside drugs for the treatment of coronavirus infections. To date, about half of antivirals have been created based on nucleosides. The majority of drugs based on nucleosides have been approved by FDA. This indicates a fruitful area for the development of novel antivirals based on nucleosides. The review describes the main features of pathogenic SARS-CoV, MERS-CoV, and SARS-CoV-2 strains, presents their comparison, considers promising approaches to creating nucleoside drugs for the treatment of coronavirus infections and provides a systematic evaluation of all the known nucleoside derivatives, which inhibit the reproduction of coronaviruses in cells. To date, two known nucleoside drugs (Remdesivir, Favipiravir) have been recommended for the treatment of SARS-CoV-2 infection and nine hit compounds based on nucleosides and their analogues have been found, one of which efficiently suppressing SARS-CoV-2 replication and eight others inhibiting SARS-CoV replication.

For the first time, N⁶-(5-phenylpentan-1-yl)adenine, a synthetic adenine derivative with a receptor-specific anticytokinin effect, was obtained. This compound exhibits a pronounced anticytokinin effect, reducing cytokinin-induced expression of the GUS reporter gene when interacting with the cytokinin receptor CRE1/AHK4 of the model plant Arabidopsis thaliana. This effect manifests itself much weaker with the related AHK2 receptor and is not observed at all with the AHK3 receptor. We showed that N⁶-(5-phenylpentan-1-yl)adenine does not bind to the ligand-binding sites of the Arabidopsis cytokinin receptors, which does not allow it to be classified as a true cytokinin antagonist. Despite the currently unknown mechanism of action, this compound may find its use as a component of plant growth regulators. Like true anticytokinins, it enhances root growth of Arabidopsis seedlings, apparently suppressing the action of endogenous cytokinins on the “root” receptor CRE1/AHK4.

Inhibition of human DNA repair enzyme tyrosyl-DNA phosphodiesterase 1 (Tdp1) by different chiral lipophilic nucleoside derivatives was studied. New Tdp1 inhibitors were found in the series of the studied compounds with IC₅₀ = 2.7–6.7 μM. It was shown that D-lipophilic nucleoside derivatives manifested higher inhibition activity than their L-analogs, and configuration of the carbohydrate moiety can influence the mechanism of Tdp1 inhibition.

The enzymatic synthesis of nucleoside derivatives is an important alternative to multi-step chemical methods traditionally used for this purpose. Despite several undeniable advantages of the enzymatic approach, there are a number of factors limiting its application, such as the limited substrate specificity of enzymes, the need to work at fairly low concentrations, and the physicochemical properties of substrates—for example, low solubility. This research conducted by our group is dedicated to the advantages and limitations of using purine nucleoside phosphorylases (PNPs), the main enzymes for the metabolic reutilization of purines, in the synthesis of modified nucleoside analogues. In our work, the substrate specificity of PNP from various bacterial sources (mesophilic and thermophilic) was studied, and the effect of substrate, increased temperature, and the presence of organic solvents on the conversion rate was investigated.

A comparative analysis of the transglycosylation conditions catalyzed by E. coli nucleoside phosphorylases, leading to the formation of 2′-deoxynucleosides, was performed. We demonstrated that maximal yields of 2′-deoxynucleosides, especially modified, can be achieved under small excess of glycosyl-donor (7-methyl-2′-deoxyguanosine, thymidine) and a 4-fold lack of phosphate. A phosphate concentration less than equimolar one allows using only a slight excess of the carbohydrate residue donor nucleoside to increase the reaction’s output. A three-step methodology was elaborated for the preparative synthesis of purine-modified 2′-deoxyribonucleosides, starting from the corresponding ribonucleosides.