Fragment-based approach to novel bioactive purine derivatives

Using purine as a scaffold, the methods for preparation of novel 2-aminopurine and purine derivatives substituted at position C6 by the fragments of natural amino acids, short peptides, andN-heterocycles, including enantiopure ones, have been proposed. The methods for determination of the enantiomeric purity of the obtained chiral compounds have been developed. Conjugates exhibiting high antimycobacterial or antiherpesvirus activity against both laboratory and multidrug-resistant strains were revealed among the obtained compounds. © 2020 De Gruyter. All rights reserved.Russian Science Foundation, RSF: 19-13-00231Funding : The reviewed studies were financially supported by the Russian Science Foundation (project no. 19-13-00231)

Антивирусный эффект нового конъюгата пурина LAS-131 в отношении вируса простого герпеса 1 типа (Herpesviridae: Alphaherpesvirinae: Simplexvirus: Human alphaherpesvirus 1) in vitro

Introduction. Herpes simplex viruses type 1 (HSV-1) are extremely widespread throughout the world and, similar to other herpesviruses, establish lifelong persistent infection in the host. Reactivating sporadically, HSV-1 elicits recurrences in both immunocompetent and immunocompromised individuals and can cause serious diseases (blindness, encephalitis, generalized infections). The currently available antiherpetic drugs that aimed mainly at suppressing replication of viral DNA are not always effective enough, for example, due to the development of drug resistance. As we showed earlier the newly discovered compound LAS-131 exhibits the strong and highly selective inhibitory activity against HSV-1, including strain resistant to acyclovir (selective index, SI = 63). The presence of LAS-131 at a concentration of 20 μg/ml leads to a decrease in the titer of HSV-1 (strain L2) by 4 lg in a one round of HSV-1 replication. Material and methods. To establish the step(s) of the virus life cycle that is sensitive to the action of LAS-131, we have applied a widely used approach, that made it possible to determine how long the addition of a compound can be postponed before it loses its antiviral activity (time-of-addition assay), and to compare this indicator with the crucial time of application of inhibitors with a well-known mechanism of action (in cell culture). Results. It has been shown for the first time that LAS-131 retains a pronounced antiviral effect when introduced into the experimental system no later than 9 hours post-infection (p.i.). However, LAS-131 does not affect the release of HSV-1 from the cell. Discussion. Together with published data on the termination of the synthesis of viral DNA 9–12 h after the adsorption in a cell culture infected with HSV with a high multiplicity (≥1 PFU/cell), our results suggest that LAS-131 interferes the life cycle of HSV-1 during synthesis of viral DNA. Further studies of the mechanism of action are necessary to establish definitely the biological target for this compound,. © 2020 Izdatel'stvo Meditsina. All rights reserved

Stereochemical aspects in the synthesis of novel N-(purin-6-yl)dipeptides as potential antimycobacterial agents

The synthesis of purine conjugates with natural amino acids is one of the promising directions in search for novel therapeutic agents, including antimycobacterial agents. The purpose of this study was to synthesize N-(purin-6-yl)dipeptides containing the terminal fragment of (S)-glutamic acid. To obtain the target compounds, two synthetic routes were tested. The first of them is based on coupling of N-(purin-6-yl)-(S)-amino acids to dimethyl (S)-glutamate in the presence of carbodiimide coupling agent followed by the removal of ester groups. However, it turned out that this coupling process was accompanied by racemization of the chiral center of N-(purin-6-yl)-α-amino acids and in all cases led to mixtures of (S,S)- and (R,S)-diastereomers (6:4). Individual (S,S)-diastereomers were obtained using an alternative approach based on the nucleophilic substitution of chlorine in 6-chloropurine or 2-amino-6-chloropurine with corresponding dipeptides as nucleophiles. The enantiomeric purity of the target compounds was confirmed by chiral HPLC. To test the assumption that racemization of the chiral center of N-(purin-6-yl)-α-amino acids occurs with the participation of nitrogen atoms of the imidazole ring via the stage of formation of a chirally labile intermediate, we obtained such structural analogs of N-(purin-6-yl)-(S)-alanine as N-(9-benzylpurin-6-yl)-(S)-alanine and N-(7-deazapurin-6-yl)-(S)-alanine. It was found that coupling of these compounds to dimethyl (S)-glutamate was also accompanied by racemization. This indicates that the imidazole fragment does not play a crucial role in this process. When testing the antimycobacterial activity of some of the obtained compounds, conjugates with moderate activity against the laboratory Mycobacterium tuberculosis H37Rv strain (MIC 3.1–6.25 μg/mL) were identified. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, AT part of Springer Nature.The work was financially supported by the Russian Science Foundation (Grant 19-13-00231). We are grateful to Dr. Marionella A. Kravchenko [Ural Research Institute of Phthisiopulmonology (National Medical Research Center, Ministry of Healthcare of the Russian Federation, Ekaterinburg, Russia)] for conducting biological trials. Analytical studies were carried out using equipment of the Centre for Joint Use ?Spectroscopy and Analysis of Organic Compounds? at the Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences

Synthesis of Pyrimidine Conjugates with 4-(6-Amino-hexanoyl)-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4] benzoxazine and Evaluation of Their Antiviral Activity

A series of pyrimidine conjugates containing a fragment of racemic 7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine and its (S)-enantiomer attached via a 6-aminohexanoyl fragment were synthesized by the reaction of nucleophilic substitution of chlorine in various chloropyrimidines. The structures of the synthesized compounds were confirmed by1H,19F, and 13 C NMR spectral data. Enantiomeric purity of optically active derivatives was confirmed by chiral HPLC. Antiviral evaluation of the synthesized compounds has shown that the replacement of purine with a pyrimidine fragment leads to a decrease in the anti-herpesvirus activity compared to the lead compound, purine conjugate. The studied compounds did not exhibit significant activity against influenza A (H1N1) virus. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 19-13-00231-PFunding: This research was funded by the Russian Science Foundation, grant number 19-13-00231-P

Stereochemical aspects in the synthesis of novel N-(purin-6-yl)dipeptides as potential antimycobacterial agents

The synthesis of purine conjugates with natural amino acids is one of the promising directions in search for novel therapeutic agents, including antimycobacterial agents. The purpose of this study was to synthesize N-(purin-6-yl)dipeptides containing the terminal fragment of (S)-glutamic acid. To obtain the target compounds, two synthetic routes were tested. The first of them is based on coupling of N-(purin-6-yl)-(S)-amino acids to dimethyl (S)-glutamate in the presence of carbodiimide coupling agent followed by the removal of ester groups. However, it turned out that this coupling process was accompanied by racemization of the chiral center of N-(purin-6-yl)-α-amino acids and in all cases led to mixtures of (S,S)- and (R,S)-diastereomers (6:4). Individual (S,S)-diastereomers were obtained using an alternative approach based on the nucleophilic substitution of chlorine in 6-chloropurine or 2-amino-6-chloropurine with corresponding dipeptides as nucleophiles. The enantiomeric purity of the target compounds was confirmed by chiral HPLC. To test the assumption that racemization of the chiral center of N-(purin-6-yl)-α-amino acids occurs with the participation of nitrogen atoms of the imidazole ring via the stage of formation of a chirally labile intermediate, we obtained such structural analogs of N-(purin-6-yl)-(S)-alanine as N-(9-benzylpurin-6-yl)-(S)-alanine and N-(7-deazapurin-6-yl)-(S)-alanine. It was found that coupling of these compounds to dimethyl (S)-glutamate was also accompanied by racemization. This indicates that the imidazole fragment does not play a crucial role in this process. When testing the antimycobacterial activity of some of the obtained compounds, conjugates with moderate activity against the laboratory Mycobacterium tuberculosis H37Rv strain (MIC 3.1–6.25 μg/mL) were identified

Synthesis and Cytotoxic Activity of the Derivatives of <i>N</i>-(Purin-6-yl)aminopolymethylene Carboxylic Acids and Related Compounds

Testing a number of N-[omega-(purin-6-yl)aminoalkanoyl] derivatives of 7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine in a panel of nine tumor cell lines has shown that the studied compounds exhibit high cytotoxic activity, especially against 4T1 murine mammary carcinoma, COLO201 human colorectal adenocarcinoma, SNU-1 human gastric carcinoma, and HepG2 human hepatocellular carcinoma cells. Synthesis and study of structural analogs of these compounds made it possible to find that the presence of both a difluorobenzoxazine fragment and a purine residue bound via a linker of a certain length is crucial for the manifestation of the cytotoxic activity of this group of compounds. The study of the effect of the most promising compound on the cell cycle of the human tumor cell lines, the most sensitive and least sensitive to cytotoxic action (MDA-MB-231 breast adenocarcinoma and COLO201 colorectal adenocarcinoma, respectively), allows us to conclude that this compound is an inhibitor of DNA biosynthesis. The found group of purine conjugates may be of interest in the design of new antitumor agents