Selenoacyclovir and Selenoganciclovir: Discovery of a New Template for Antiviral Agents

TCCA/RSeSeR-Mediated Selenoalkoxy of Allenamides via a Radical Process: Synthesis of Selanyl-allylic N,O-Aminals

An efficient TCCA (trichloroisocyanuric acid)/RSeSeR-mediated selenoalkoxy of allenamides for the construction of selanyl-allylic N,OA-aminal derivatives was developed. The reaction exhibits good functional group tolerance and high efficiency, affording the products in good to excellent yields. Mechanistic investigations indicated that a selanyl-allylic radical intermediate was first formed via the RSe radical added to the central carbon of allenamides, which subsequently furnished highly stable selanyl-allylic carbocation intermediate by abstraction of an electron by the chlorine radical. Moreover, this is the first report of using selenium reagent (RSeCl) to activate allenamides via a radical process.

Enzyme-Catalyzed Regioselective Synthesis of 4-Hetero-Functionalized 1,5-Disubstituted 1,2,3-Triazoles

Enzyme-catalyzed novel protocols for the regioselective construction of fully substituted 1,2,3-triazoles by employing 2-azido-1,3,5-triazine (ADT) as a 1,3-dipole for the cycloaddition reaction with the activated alkene in an aqueous medium have been developed. Various 4-heterosubstituted-1,2,3-triazoles were readily assembled in good to excellent yields with high regioselectivity. This reaction also features wide substrate scope, strong functional group tolerance, gram-scale synthesis, and an environmentally friendly process.

Organoselenium Compounds in Medicinal Chemistry

The chemical and biological interest in this element and the molecules bearing selenium has been exponentially growing over the years. Selenium, formerly designated as a toxin, becomes a vital trace element for life that appears as selenocysteine and its dimeric form, selenocystine, in the active sites of selenoproteins, which catalyze a wide variety of reactions, including the detoxification of reactive oxygen species and modulation of redox activities. From the point of view of drug developments, organoselenium drugs are isosteres of sulfur-containing and oxygen-containing drugs with the advantage that the presence of the selenium atom confers antioxidant properties and high lipophilicity, which would increase cell membrane permeation leading to better oral bioavailability. This statement is the paramount relevance considering the big number of clinically employed compounds bearing sulfur or oxygen atoms in their structures including nucleosides and carbohydrates. Thus, in this article we have focused on the relevant features of the application of selenium in medicinal chemistry. With the increasing interest in selenium chemistry, we have attempted to highlight the most significant published data on this subject, mainly concentrating the analysis on the last years. In consequence, the recent advances of relevant pharmacological organoselenium compounds are discussed.

The antiherpetic and anti-inflammatory activity of the frog-derived peptide Hylin-a1

AIM

The high incidence of virus-related infections and the large diffusion of drug-resistant pathogens stimulate the search and identification of new antiviral agents with a broad spectrum of action. Antivirals can be designed to act on a single target by interfering with a specific step in the viral lifecycle. On the contrary, antiviral peptides (AVPs) are known for acting on a wide range of viruses, with a diversified mechanism of action targeting virus and/or host cell. In the present study, we evaluated the antiviral potential of the peptide Hylin-a1 secreted by the frog Hypsiobas albopunctatus against members of the Herpesviridae family.

METHODS AND RESULTS

The inhibitory capacity of the peptide was evaluated in vitro by plaque assays in order to understand the possible mechanism of action. The results were also confirmed by real-time PCR and Western blot evaluating the expression of viral genes. Hylin-a1 acts to block the herpetic infection interfering at the early stages of both herpes simplex virus type 1 (HSV-1) and type 2 infection. Its mechanism is mainly directed on the membrane, probably by damaging the viral envelope. The same effect was also observed against HSV-1 strains resistant to acyclovir.

CONCLUSIONS

The data presented in this study, such as the increased activity of the peptide when combined to acyclovir, a weak hemolytic profile, an anti-inflammatory effect, and a tolerable half-life in serum, indicates Hylin-a1 as a novel antiherpetic molecule with promising potential in the clinical setting.

Selenization of Small Molecule Drugs: A New Player on the Board

There is an urgent need to develop safer and more effective modalities for the treatment of a wide range of pathologies due to the increasing rates of drug resistance, undesired side effects, poor clinical outcomes, etc. Throughout the years, selenium (Se) has attracted a great deal of attention due to its important role in human health. Besides, a growing body of work has unveiled that the inclusion of Se motifs into a great number of molecules is a promising strategy for obtaining novel therapeutic agents. In the current Perspective, we have gathered the most recent literature related to the incorporation of different Se moieties into the scaffolds of a wide range of known drugs and their feasible pharmaceutical applications. In addition, we highlight different representative examples as well as provide our perspective on Se drugs and the possible future directions, promises, opportunities, and challenges of this ground-breaking area of research.

Electrochemical Oxidative Difunctionalization of Diazo Compounds with Diselenides and Nucleophiles

An electrochemical oxidative difunctionalization of diazo compounds with diselenides and nucleophiles has been developed. This innovative approach yields a diverse array of selenium-containing pyrazole esters and alkoxy esters, overcoming the limitations of traditional synthesis methods. Remarkably, various nucleophiles, including acids, alcohols, and pyrazoles, can be seamlessly incorporated. Notably, this protocol boasts high atom efficiency, excellent functional group tolerance, and good efficiency and operates under transition metal- and oxidant-free conditions, distinguishing it in the field.

Structural and Synthetic Aspects of Small Ring Oxa- and Aza-Heterocyclic Ring Systems as Antiviral Activities

Antiviral properties of different oxa- and aza-heterocycles are identified and properly correlated with their structural features and discussed in this review article. The primary objective is to explore the activity of such ring systems as antiviral agents, as well as their synthetic routes and biological significance. Eventually, the structure-activity relationship (SAR) of the heterocyclic compounds, along with their salient characteristics are exhibited to build a suitable platform for medicinal chemists and biotechnologists. The synergistic conclusions are extremely important for the introduction of a newer tool for the future drug discovery program.

Antiviral activities of Artemisia vulgaris L. extract against herpes simplex virus

BACKGROUND

Artemisia vulgaris L. is often used as a traditional Chinese medicine with the same origin of medicine and food. Its active ingredient in leaves have multiple biological functions such as anti-inflammatory, antibacterial and insecticidal, anti-tumor, antioxidant and immune regulation, etc. It is confirmed that folium Artemisiae argyi has obvious anti-HBV activity, however, its antiviral activity and mechanism against herpesvirus or other viruses are not clear. Hence, we aimed to screen the crude extracts (Fr.8.3) isolated and extracted from folium A. argyi to explore the anti-herpesvirus activity and mechanism.

METHODS

The antiherpes virus activity of Fr.8.3 was mainly characterized by cytopathic effects, real-time PCR detection of viral gene replication and expression levels, western blotting, viral titer determination and plaque reduction experiments. The main components of Fr.8.3 were identified by using LC-MS, and selected protein targets of these components were investigated through molecular docking.

RESULTS

We collected and isolated a variety of A. vulgaris L. samples from Tangyin County, Henan Province and then screened the A. vulgaris L. leaf extracts for anti-HSV-1 activity. The results of the plaque reduction test showed that the crude extract of A. vulgaris L.-Fr.8.3 had anti-HSV-1 activity, and we further verified the anti-HSV-1 activity of Fr.8.3 at the DNA, RNA and protein levels. Moreover, we found that Fr.8.3 also had a broad spectrum of antiviral activity. Finally, we explored its anti-HSV-1 mechanism, and the results showed that Fr.8.3 exerted an anti-HSV-1 effect by acting directly on the virus itself. Then, the extracts were screened on HSV-1 surface glycoproteins and host cell surface receptors for potential binding ability by molecular docking, which further verified the phenotypic results. LC-MS analysis showed that 1 and 2 were the two main components of the extracts. Docking analysis suggested that compounds from extract 1 might similarly cover the binding domain between the virus and the host cells, thus interfering with virus adhesion to cell receptors, which provides new ideas and insights for clinical drug development for herpes simplex virus type 1.

CONCLUSION

We found that Fr.8.3 has anti-herpesvirus and anti-rotavirus effects. The main 12 components in Fr.8.3 were analyzed by LC-MS, and the protein targets were finally predicted through molecular docking, which showed that alkaloids may play a major role in antiviral activity.

Recent Advances in Light-Induced Selenylation

Selenium-containing organic molecules have recently found a plethora of applications, ranging from organic synthesis to pharmacology and material sciences. In view of these concepts, the development of mild, efficient, and general protocols for the formation of C-Se bonds is desirable, and light induced approaches are appealing ways. The aim of this Review is to provide the reader with the most recent examples of light promoted selenylation processes.

Crystal structure of 1-isopropyl-3-(prop-1-en-2-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine, C11H15N5

C11H15N5, monoclinic, P21/c (no. 14), a = 9.5677(16) Å, b = 8.1755(15) Å, c = 14.846(3) Å, β = 93.783(4)°, V = 1158.7(4) Å3, Z = 4, R gt (F) = 0.0473, wR ref (F 2) = 0.1425, T = 173 K.

Incorporating Selenium into Heterocycles and Natural Products─From Chemical Properties to Pharmacological Activities

Selenium (Se)-containing compounds have emerged as potential therapeutic agents for the treatment of a range of diseases. Through tremendous effort, considerable knowledge has been acquired to understand the complex chemical properties and biological activities of selenium, especially after its incorporation into bioactive molecules. From this perspective, we compiled extensive literature evidence to summarize and critically discuss the relationship between the pharmacological activities and chemical properties of selenium compounds and the strategic incorporation of selenium into organic molecules, especially bioactive heterocycles and natural products. We also provide perspectives regarding the challenges in selenium-based medicinal chemistry and future research directions.

Visible-Light-Induced, Graphene Oxide-Promoted C3-Chalcogenylation of Indoles Strategy under Transition-Metal-Free Conditions

An efficient and general method for the synthesis of 3-sulfenylindoles and 3-selenylindoles employing visible-light irradiation with graphene oxide as a promoter at room temperature has been achieved. The reaction features are high yields, simple operation, metal-free and iodine-free conditions, an easy-to-handle oxidant, and gram-scalable synthesis. This simple protocol allows one to access a wide range of 3-arylthioindoles, 3-arylselenylindoles, and even 3-thiocyanatoindoles with good to excellent yields.

Identification of a pyridine derivative of diselenides as a potent inhibitor of the main protease of SARS-CoV-2 through in silico screening and biochemical evaluation

Among the 22 organoselenium compounds studied, 2-Py2Se2 & Nict2Se2 showed the highest affinity for Mpro. The biochemical studies confirmed their superiority as compared to standard compound like Ebselen in terms of the IC50 required for Mpro inhibition.

Mild and Expeditious Synthesis of Sulfenyl Enaminones of l-α-Amino Esters and Aryl/Alkyl Amines through NCS-Mediated Sulfenylation

Sulfenylation or selenylation of enaminones of l-α-amino esters requires mild reaction conditions due to the presence of a racemization-prone chiral center and reactive side chains. An N-chlorosuccinimide (NCS)-mediated methodology has been developed for rapid sulfenylation of enaminones of l-α-amino esters and aryl/alkyl amines at room temperature in open air under metal-free conditions. Enaminones of l-α-amino esters bearing aliphatic, aromatic, and heterocyclic side chains react efficiently with diverse aryl/alkyl/heteroaryl thiols (R1SH) in the presence of NCS to afford a library of biologically important sulfenyl enaminones in good-to-excellent yields (71-90%). Under similar reaction conditions, the enaminones also react with benzeneselenol to produce selenyl enaminones in good yield (73-83%). The NCS-mediated pathway generates sulfenyl chloride (R1SCl) as an intermediate which leads to rapid sulfenylation of enaminones through cross-dehydrogenative coupling (CDC) under mild reaction conditions.

Preparation of selenyl 1,3-oxazines via PhICl2/Cu2O-promoted aminoselenation of O-homoallyl benzimidates with diselenides

A practical electrophilic aminoselenation of O-homoallyl benzimidate with diselenides promoted by PhICl₂/Cu₂O has been developed. The easily available and stable diselenides were used as selenium sources. Various selenyl 1,3-oxazines, which are important frameworks in medicinal and biological chemistry, were easily obtained in moderate to good yields for the first time. Easy scaleup and scalability make this method attractive for the preparation of other valuable organoselenides.

Insight for Immunotherapy of HCMV Infection

Human cytomegalovirus (HCMV), a ubiquitous in humans, has a high prevalence rate. Young people are susceptible to HCMV infection in developing countries, while older individuals are more susceptible in developed countries. Most patients have no obvious symptoms from the primary infection. Studies have indicated that the virus has gradually adapted to the host immune system. Therefore, the control of HCMV infection requires strong immune modulation. With the recent advances in immunotherapy, its application to HCMV infections is receiving increasing attention. Here, we discuss the immune response to HCMV infection, the immune escape mechanism, and the different roles that HCMV plays in various types of immunotherapy, including vaccines, adoptive cell therapy, checkpoint blockade therapy, and targeted antibodies.

Small molecule selenium-containing compounds: Recent development and therapeutic applications

Selenium (Se) is an essential micronutrient of organism and has important function. It participates in the functions of selenoprotein in several manners. In recent years, Se has attracted much attention because of its therapeutic potential against several diseases. Many natural and synthetic organic Se-containing compounds were studied and explored for the treatment of cancer and other diseases. Studies have showed that incorporation of Se atom into small molecules significantly enhanced their bioactivities. In this paper, according to different applications and structural characteristics, the research progress and therapeutic application of Se-containing compounds are reviewed, and more than 110 Se-containing compounds were selected as representatives which showed potent activities such as anticancer, antioxidant, antifibrolytic, antiparasitic, antibacterial, antiviral, antifungal and central nervous system related effects. This review is expected to provide a basis for further study of new promising Se-containing compounds.

Optimized Biocatalytic Synthesis of 2-Selenopyrimidine Nucleosides by Transglycosylation*

Selenium-modified nucleosides are powerful tools to study the structure and function of nucleic acids and their protein interactions. The widespread application of 2-selenopyrimidine nucleosides is currently limited by low yields in established synthetic routes. Herein, we describe the optimization of the synthesis of 2-Se-uridine and 2-Se-thymidine derivatives by thermostable nucleoside phosphorylases in transglycosylation reactions using natural uridine or thymidine as sugar donors. Reactions were performed at 60 or 80 °C and at pH 9 under hypoxic conditions to improve the solubility and stability of the 2-Se-nucleobases in aqueous media. To optimize the conversion, the reaction equilibria in analytical transglycosylation reactions were studied. The equilibrium constants of phosphorolysis of the 2-Se-pyrimidines were between 5 and 10, and therefore differ by an order of magnitude from the equilibrium constants of any other known case. Hence, the thermodynamic properties of the target nucleosides are inherently unfavorable, and this complicates their synthesis significantly. A tenfold excess of sugar donor was needed to achieve 40-48 % conversion to the target nucleoside. Scale-up of the optimized conditions provided four Se-containing nucleosides in 6-40 % isolated yield, which compares favorably to established chemical routes.

Purine Nucleoside Derivatives Containing a Sulfa Ethylamine Moiety: Design, Synthesis, Antiviral Activity, and Mechanism

To find efficient and broad-spectrum viral agents, a series of purine nucleoside derivatives containing sulfa ethylamine moieties was designed and synthesized, and their antiviral activities against tobacco mosaic virus (TMV), cucumber mosaic virus (CMV), and potato virus Y (PVY) were evaluated. Some target compounds displayed good antiviral activities. Among them, compound 3 showed excellent protective activity against CMV and PVY with 50% effective concentration values (EC₅₀) of 137 and 209 μg/mL, respectively, which were better than that of the control agent ningnanmycin (508 and 431 μg/mL). Moreover, the EC₅₀ value of compound 3 for the inactivating activity against TMV was 48 μg/mL, which was better than that of ningnanmycin (88 μg/mL). In addition, compound 3 not only destroyed the structure of the TMV virus but also had a good interaction with the coat protein of the TMV virus. Therefore, compound 3 may further destroy the structure of the virus by binding to the coat protein of the TMV virus, thereby weakening the infectivity of the virus.

Selenium-Containing Polysaccharides—Structural Diversity, Biosynthesis, Chemical Modifications and Biological Activity

Selenosugars are a group of sugar derivatives of great structural diversity (e.g., molar masses, selenium oxidation state, and selenium binding), obtained as a result of biosynthesis, chemical modification of natural compounds, or chemical synthesis. Seleno-monosaccharides and disaccharides are known to be non-toxic products of the natural metabolism of selenium compounds in mammals. In the case of the selenium-containing polysaccharides of natural origin, their formation is also postulated as a form of detoxification of excess selenium in microorganisms, mushroom, and plants. The valency of selenium in selenium-containing polysaccharides can be: 0 (encapsulated nano-selenium), IV (selenites of polysaccharides), or II (selenoglycosides or selenium built into the sugar ring to replace oxygen). The great interest in Se-polysaccharides results from the expected synergy between selenium and polysaccharides. Several plant- and mushroom-derived polysaccharides are potent macromolecules with antitumor, immunomodulatory, antioxidant, and other biological properties. Selenium, a trace element of fundamental importance to human health, has been shown to possess several analogous functions. The mechanism by which selenium exerts anticancer and immunomodulatory activity differs from that of polysaccharide fractions, but a similar pharmacological effect suggests a possible synergy of these two agents. Various functions of Se-polysaccharides have been explored, including antitumor, immune-enhancement, antioxidant, antidiabetic, anti-inflammatory, hepatoprotective, and neuroprotective activities. Due to being non-toxic or much less toxic than inorganic selenium compounds, Se-polysaccharides are potential dietary supplements that could be used, e.g., in chemoprevention.

Meyer-Schuster-Type Rearrangement of Propargylic Alcohols into α-Selenoenals and -enones with Diselenides

We describe a mild and broadly applicable protocol for the preparation of a diverse array of multisubstituted α-selenoenals and -enones from readily accessible propargylic alcohols and diselenides. The transformation proceeds via the Selectfluor-promoted selenirenium pathway, which enables selenenylation/rearrangement of a variety of propargylic alcohols. Gram-scale experiments showed the potential of this synergistic protocol for practical application.

Synthesis and biological activity of selenopsammaplin A and its analogues as antitumor agents with DOT1L inhibitory activity

Disruptor of telomeric silencing-1 like (DOT1L) is a histone H3 methyltransferase which specifically catalyzes the methylation of histone H3 lysine-79 residue. Recent findings demonstrate that DOT1L is abnormally overexpressed and the upregulated DOT1L evokes the proliferation and metastasis in human breast cancer cells. Therefore, the DOT1L inhibitor is considered a promising strategy to treat breast cancers. Non-nucleoside DOT1L inhibitors, selenopsammaplin A and its analogues, were firstly reported in the present study. Selenopsammaplin A was newly designed and synthesized with 25% overall yield in 8 steps from 3-bromo-4-hydroxybenzaldahyde, and thirteen analogues of selenopsammaplin A were prepared for structure-activity relationship studies of their cytotoxicity against cancer cells and inhibitory activity toward DOT1L for antitumor potential. All synthetic selenopsammaplin A analogues exhibited the higher cytotoxicity compared to psammaplin A with up to 6 - 60 times depending on cancer cells, and most analogues showed significant inhibitory activities against DOT1L. Among the prepared analogues, the phenyl analogue (10) possessed the most potent activity with both cytotoxicity and inhibition of DOT1L. Compound 10 also exhibited the antitumor and antimetastatic activity in an orthotopic mouse metastasis model implanted with MDA-MB-231 human breast cancer cells. These biological findings suggest that analogue 10 is a promising candidate for development as a cancer chemotherapeutic agent in breast cancers.

The innovative potential of selenium-containing agents for fighting cancer and viral infections

Selenium-containing compounds have emerged as a potentially promising treatment for viral infections and tumor development and dissemination. Selenium per se is often considered as a toxic element with little or no beneficial effects, but considerable advances have been made in the understanding of the complex biology, chemistry and drug delivery of this element, especially when it is included in bioactive molecules. Here, we summarize and critically discuss recent findings in the field of selenium-based applications for the treatment of cancer and viral infections.

Copper/DTBP-Promoted Oxyselenation of Propargylic Amines with Diselenides and CO2: Synthesis of Selenyl 2-Oxazolidinones

A highly efficient electrophilic oxyselenation of propargylic amines with diselenides and CO₂ under atmospheric pressure promoted by copper/DTBP is reported. Various biologically important selenyl 2-oxazolidinones were produced in moderate to excellent yields. The developed method features a broad substrate scope, easy scalability, and mild reaction conditions.

The direct C3 chalcogenylation of indolines using a graphene-oxide-promoted and visible-light-induced synergistic effect

A green methodology for the construction of carbon–chalcogen (S and Se) bonds via a GO-promoted and metal-free light-induced synergistic effect is demonstrated.

Antiviral, Antimicrobial and Antibiofilm Activity of Selenoesters and Selenoanhydrides

Selenoesters and the selenium isostere of phthalic anhydride are bioactive selenium compounds with a reported promising activity in cancer, both due to their cytotoxicity and capacity to reverse multidrug resistance. Herein we evaluate the antiviral, the biofilm inhibitory, the antibacterial and the antifungal activities of these compounds. The selenoanhydride and 7 out of the 10 selenoesters were especially potent antiviral agents in Vero cells infected with herpes simplex virus-2 (HSV-2). In addition, the tested selenium derivatives showed interesting antibiofilm activity against Staphylococcus aureus and Salmonella enterica serovar Typhimurium, as well as a moderate antifungal activity in resistant strains of Candida spp. They were inactive against anaerobes, which may indicate that the mechanism of action of these derivatives depends on the presence of oxygen. The capacity to inhibit the bacterial biofilm can be of particular interest in the treatment of nosocomial infections and in the coating of surfaces of prostheses. Finally, the potent antiviral activity observed converts these selenium derivatives into promising antiviral agents with potential medical applications.

Synthesis, Antiviral Activity, and Mechanisms of Purine Nucleoside Derivatives Containing a Sulfonamide Moiety

Novel purine nucleoside derivatives containing a sulfonamide moiety were prepared, as well as their antiviral activities against potato virus Y (PVY), cucumber mosaic virus (CMV), and tobacco mosaic virus (TMV) were evaluated. The antiviral mechanisms of the compounds were investigated. Results showed that most of the compounds had good antiviral activities. Compound 5 at 500 μg/mL exhibited excellent curative and protective activities of 52.5% and 60.0% and of 52.0% and 60.2% for PVY and CMV, respectively, which are higher than those of ningnanmycin (48.1%, 49.6%; 45.3%, 47.7%), ribavirin (38.3%, 48.2%; 40.8%, 45.5%), and chitosan oligosaccharide (32.5%, 33.8%; 35.1%, 34.6%). Moreover, compound 5 displayed good inactivating activity against TMV, with an EC₅₀ value of 48.8 μg/mL, which is better than that of ningnanmycin (84.7 μg/mL), ribavirin (150.4 μg/mL), and chitosan oligosaccharide (521.3 μg/mL). The excellent antiviral activity of compound 5 is related to its immune induction effect which can regulate the physiological and biochemical processes in plants, including defense-related enzyme activities, defense-related genes, and photosynthesis-related proteins. These results indicate that purine nucleoside derivatives containing a sulfonamide moiety are worthy of further research and development as new antiviral agents.

Antiviral properties and interaction of novel chalcone derivatives containing a purine and benzenesulfonamide moiety

A new concise and facile method was explored to synthesize a series of novel chalcone derivatives containing a purine and benzenesulfonamide moiety and their antiviral properties were evaluated against TMV and CMV. Biological assays indicated that several of the derivatives exhibited significant anti-TMV and anti-CMV activities in vivo. In particular, compound d2 displayed excellent inactivating activity against TMV, with the EC50 value of 51.65 μg/mL, which was better than that of ribavirin (150.45 μg/mL). Molecular docking showed that there are four hydrogen bonds between compound d2 and TMV coat protein (TMV-CP). Compound d2 demonstrated strong binding capacity to TMV-CP with Ka = 1.58 × 105 L/mol and Kd = 12.16 μM. These findings indicated that chalcone derivatives are worthy of further research and development as templates for new antiviral agents.

Copper-Catalyzed Decarboxylative/Click Cascade Reaction: Regioselective Assembly of 5-Selenotriazole Anticancer Agents

A simple and efficient Cu-catalyzed decarboxylative/click reaction for the preparation of 1,4-disubstituted 5-arylselanyl-1,2,3-triazoles from propiolic acids, diselenides, and azides has been developed. The mechanistic study revealed that the intermolecular AAC reaction of an alkynyl selenium intermediate occurred. The resulting multisubstituted 5-seleno-1,2,3-triazoles were tested for in vitro anticancer activity by MTT assay, and compounds 4f, 4h, and 4p showed potent cancer cell-growth inhibition activities.

Structure-Activity Relationships of Acyclic Selenopurine Nucleosides as Antiviral Agents

A series of acyclic selenopurine nucleosides 3a–f and 4a–g were synthesized based on the bioisosteric rationale between oxygen and selenium, and then evaluated for antiviral activity. Among the compounds tested, seleno-acyclovir (4a) exhibited the most potent anti-herpes simplex virus (HSV)-1 (EC₅₀ = 1.47 µM) and HSV-2 (EC₅₀ = 6.34 µM) activities without cytotoxicity up to 100 µM, while 2,6-diaminopurine derivatives 4e–g exhibited significant anti-human cytomegalovirus (HCMV) activity, which is slightly more potent than the guanine derivative 4d, indicating that they might act as prodrugs of seleno-ganciclovir (4d).