Synthesis and evaluation of "AZT-HEPT", "AZT-pyridinone", and "ddC-HEPT" conjugates as inhibitors of HIV reverse transcriptase

The Use of Zidovudine Pharmacophore in Multi-Target-Directed Ligands for AIDS Therapy

The concept of polypharmacology embraces multiple drugs combined in a therapeutic regimen (drug combination or cocktail), fixed dose combinations (FDCs), and a single drug that binds to different targets (multi-target drug). A polypharmacology approach is widely applied in the treatment of acquired immunodeficiency syndrome (AIDS), providing life-saving therapies for millions of people living with HIV. Despite the success in viral load suppression and patient survival of combined antiretroviral therapy (cART), the development of new drugs has become imperative, owing to the emergence of resistant strains and poor adherence to cART. 3'-azido-2',3'-dideoxythymidine, also known as azidothymidine or zidovudine (AZT), is a widely applied starting scaffold in the search for new compounds, due to its good antiretroviral activity. Through the medicinal chemistry tool of molecular hybridization, AZT has been included in the structure of several compounds allowing for the development of multi-target-directed ligands (MTDLs) as antiretrovirals. This review aims to systematically explore and critically discuss AZT-based compounds as potential MTDLs for the treatment of AIDS. The review findings allowed us to conclude that: (i) AZT hybrids are still worth exploring, as they may provide highly active compounds targeting different steps of the HIV-1 replication cycle; (ii) AZT is a good starting point for the preparation of co-drugs with enhanced cell permeability.

Advance of structural modification of nucleosides scaffold

With Remdesivir being approved by FDA as a drug for the treatment of Corona Virus Disease 2019 (COVID-19), nucleoside drugs have once again received widespread attention in the medical community. Herein, we summarized modification of traditional nucleoside framework (sugar + base), traizole nucleosides, nucleoside analogues assembled by other drugs, macromolecule-modified nucleosides, and their bioactivity rules. 2'-"Ara"-substituted by -F or -CN group, and 3'-"ara" substituted by acetylenyl group can greatly influence their anti-tumor activities. Dideoxy dehydrogenation of 2',3'-sites can enhance antiviral efficiencies. Acyclic nucleosides and L-type nucleosides mainly represented antiviral capabilities. 5-F Substituted uracil analogues exihibit anti-tumor effects, and the substrates substituted by -I, -CF3, bromovinyl group usually show antiviral activities. The sugar coupled with 1-N of triazolid usually displays anti-tumor efficiencies, while the sugar coupled with 2-N of triazolid mainly represents antiviral activities. The nucleoside analogues assembled by cholesterol, polyethylene glycol, fatty acid and phospholipid would improve their bioavailabilities and bioactivities, or reduce their toxicities.

Discovery of potential dual-target prodrugs of HIV-1 reverse transcriptase and nucleocapsid protein 7

In the present work, we described the design, synthesis and biological evaluation of a novel series of potential dual-target prodrugs targeting the HIV-1 reverse transcriptase (RT) and nucleocapsid protein 7 (NCp7) simultaneously. Among them, the most effective compound 7c was found to inhibit HIV-1 wild-type (WT) strain at double-digit nanomolar concentration (EC₅₀ = 42 nM) in MT-4 cells, and sub-micromole (EC₅₀ = 0.308 μM) to inhibit HIV-1 NL4-3 strain in TZM-bl cells. This is a significant improvement over the parent drug MT. In addition, it showed moderate inhibitory potency (EC₅₀ = 1.329 μM) against the HIV-1 K103N/Y181C double mutant strain (MT-4 cells). The metabolic stability in human plasma of compound 7c indicated that it can release the active forms of the parent drugs MT and AZT in a linear time-independent manner and turn out to be a potential prodrug.

Theoretical calculations of molecular descriptors for anticancer activities of 1, 2, 3-triazole-pyrimidine derivatives against gastric cancer cell line (MGC-803): DFT, QSAR and docking approaches

This work used quantum chemical method via DFT to calculate molecular descriptors for the development of QSAR model to predict bioactivity (IC50- 50% inhibition concentration) of the selected 1, 2, 3-triazole-pyrimidine derivatives against receptor (human gastric cancer cell line, MGC-803). The selected molecular parameters were obtained by B3LYP/6-31G∗∗. QSAR model linked the molecular parameters of the studied compounds to their cytotoxicity and reproduced their observed bioactivities against MGC-803. The calculated IC50 tailored the observed IC50 and greater than standard compound, 5-fluorouracil, suggesting that the developed QSAR model reproduced the observed bioactivity. Statistical analyses (including R2, CV. R2 andR a 2 gave 0.950, 0.970 and 0.844 respectively) revealed a very good fitness. Molecular docking studies revealed the hydrogen bonding with the amino acid residues in the binding site, as well as ligand conformations which are essential feature for ligand-receptor interactions. Therefore, the methods used in this study are veritable tools that can be employed in pharmacological and medicinal chemistry researches in designing better drugs with improve potency.

Identification of novel bifunctional HIV-1 reverse transcriptase inhibitors

Objectives

The increasing prevalence of mutations in HIV-1 reverse transcriptase (RT) that confer resistance to existing NRTIs and NNRTIs underscores the need to develop RT inhibitors with novel mode-of-inhibition and distinct resistance profiles.

Methods

Biochemical assays were employed to identify inhibitors of RT activity and characterize their mode of inhibition. The antiviral activity of the inhibitors was assessed by cell-based assays using laboratory HIV-1 isolates and MT4 cells. RT variants were purified via avidin affinity columns.

Results

Compound A displayed equal or greater potency against many common NNRTI-resistant RTs (K103N and Y181C RTs) relative to WT RT. Despite possessing certain NNRTI-like properties, such as being unable to inhibit an engineered variant of RT lacking an NNRTI-binding pocket, we found that compound A was dependent on Mg2+ for binding to RT. Optimization of compound A led to more potent analogues, which retained similar activities against WT and K103N mutant viruses with submicromolar potency in a cell-based assay. One of the analogues, compound G, was crystallized in complex with RT and the structure was determined at 2.6 Å resolution. The structure indicated that compound G simultaneously interacts with the active site (Asp186), the highly conserved primer grip region (Leu234 and Trp229) and the NNRTI-binding pocket (Tyr188).

Conclusions

These findings reveal a novel class of RT bifunctional inhibitors that are not sensitive to the most common RT mutations, which can be further developed to address the deficiency of current RT inhibitors.

Cp*Co(iii)-catalyzed amidation of olefinic and aryl C-H bonds: highly selective synthesis of enamides and pyrimidones

A highly efficient and selective synthesis of enamides via C-H amidation of N-methoxy acrylamides with dioxazolones is realized under [Cp*CoIII] catalysis. The resulting enamide can further selectively cyclize to form pyrimidones, which can also act as a directing group for a second C-H amidation. All these three classes of products were selectively delivered under controlled conditions.

Polypharmacology in HIV inhibition: can a drug with simultaneous action against two relevant targets be an alternative to combination therapy?

HIV infection still has a serious health and socio-economical impact and is one of the primary causes of morbidity and mortality all over the world. HIV infection and the AIDS pandemic are still matters of great concern, especially in less developed countries where the access to highly active antiretroviral therapy (HAART) is limited. Patient compliance is another serious drawback. Nowadays, HAART is the treatment of choice although it is not the panacea. Despite the fact that it suppresses viral replication at undetectable viral loads and prevents progression of HIV infection into AIDS HAART has several pitfalls, namely, long-term side-effects, drug resistance development, emergence of drug-resistant viruses, low compliance and the intolerance of some patients to these drugs. Moreover, another serious health concern is the event of co-infection with more than one pathogen at the same time (e.g. HIV and HCV, HBV, herpes viruses, etc). Currently, the multi-target drug approach has become an exciting strategy to address complex diseases and overcome drug resistance development. Such multifunctional molecules combine in their structure pharmacophores that may simultaneously interfere with multiple targets and their use may eventually be more safe and efficacious than that involving a mixture of separate molecules because of avoidance or delay of drug resistance, lower incidence of unwanted drug-drug interactions and improved compliance. In this review we focus on multifunctional molecules with dual activity against different targets of the HIV life cycle or able to block replication, not only of HIV but also of other viruses that are often co-pathogens of HIV. The different approaches are documented by selected examples.

Conjugation of phosphonoacetic acid to nucleobase promotes a mechanism-based inhibition

Small molecule inhibitors have a powerful blocking action on viral polymerases. The bioavailability of the inhibitor, nevertheless, often raise a significant selectivity constraint and may substantially limit the efficacy of therapy. Phosphonoacetic acid has long been known to possess a restricted potential to block DNA biosynthesis. In order to achieve a better affinity, this compound has been linked with natural nucleotide at different positions. The structural context of the resulted conjugates has been found to be crucial for the acquisition by DNA polymerases. We show that nucleobase-conjugated phosphonoacetic acid is being accepted, but this alters the processivity of DNA polymerases. The data presented here not only provide a mechanistic rationale for a switch in the mode of DNA synthesis, but also highlight the nucleobase-targeted nucleotide functionalization as a route for enhancing the specificity of small molecule inhibitors.

Dual-targeted anti-TB/anti-HIV heterodimers

HIV and M. tuberculosis are two intersecting epidemics making the search for new dual action drugs against both pathogens extremely important. Here, we report on the synthesis and suppressive activities of five dual-targeted HIV/TB compounds. These compounds are heterodimers of AZT, as anti-HIV molecules, and 5-substituted uracil derivatives, as anti-TB molecules. We found that these compounds inhibit the growth of M. tuberculosis and suppress the replication of HIV in human cell cultures and human lymphoid tissues ex vivo. We identified one particular heterodimer that inhibited both HIV and the drug-resistant TB strain MS-115 most potently. This compound demonstrated low toxicity and had no cytostatic effect on cells in culture, constituting an ideal candidate for future development and further in vivo testing.

Ultrasonic-assisted synthesis of 1,4-disubstituted 1,2,3-triazoles via various terminal acetylenes and azide and their quorum sensing inhibition

An efficient synthesis of 1,4-disubstituted 1,2,3-triazole derivatives was studied. 1,4-Disubstituted 1,2,3-triazoles containing isoxazole and thymidine structures were synthesized in 84-96% yields starting from various terminal isoxazole ether alkynes and β-thymidine azide derivatives via a 1,3-dispolar cycloaddition using copper acetate, sodium ascorbate as the catalyst under ultrasonic assisted condition. All the target compounds were characterized by HRMS, FT-IR, ¹H NMR and ¹³C NMR spectroscopy. Furthermore, the quorum sensing inhibitory activities of synthesized compounds were evaluated with Chromobacterium violaceum (C. Violaceum CV026) based on their inhibition of violacein production, with compound C₁₀-HSL as a positive control. The compounds 8a, 8c and 8f exhibited considerable levels of inhibitory activity against violacein production, and IC₅₀ values were 217±19, 223±20 and 42.8±4.5μM, respectively, which highlighted the potential of these compounds as lead structures for further research towards the development of novel QS inhibitors.

Structure-Activity Relationship Studies on a Novel Family of Specific HIV-1 Reverse Transcriptase Inhibitors

We have previously reported the discovery and preliminary structure-activity relationships of a new class of specific HIV-1 reverse transcriptase (RT) inhibitors whose prototype compound is the 1-[2′,5′-bis- O-( tert-butyldimethylsilyl)-β-D-ribofuranosyl]-3- N-[(carboxy) methyl]-thymine. In an attempt to increase the inhibitory efficacy against HIV-1 RT of this new class of nucleosides, and to further explore the structural features required for anti-HIV-1 activity, different types of modifications have been carried out on the prototype compound. These include substitution of the tert-butyldimethylsilyl groups by other liphophilic groups, replacement of the carboxy group at the N-3 position of the nucleobase by other functional groups, change in the length of the spacer between the thymine and the carboxylic acid residue and substitution of the thymine moiety by other pyrimidine (uracil, 5-ethyluracil) or purine (hypoxanthine) nucleobases. In addition, the most salient structural features of this new class of HIV-1-specific nucleosides have been incorporated into classical HIV RT nucleoside inhibitors such as ddI, AZT, d4T. Our studies demonstrate that both the carboxymethyl moiety at the nucleobase and tert-butyldimethylsilyl groups at the sugar are important structural components since deletion of either of them is detrimental to the antiviral activity.

A new antiviral: chimeric 3TC-AZT phosphonate efficiently inhibits HIV-1 in human tissues ex vivo

Although more-recently developed antivirals target different molecules in the HIV-1 replication cycle, nucleoside reverse transcriptase inhibitors (NRTIs) remain central for HIV-1 therapy. Here, we test the anti-HIV activity of a phosphonate chimera of two well-known NRTIs, namely AZT and 3TC. We show that this newly synthesized compound suppressed HIV-1 infection in lymphoid tissue ex vivo more efficiently than did other phosphonates of NRTIs. Moreover, the new compound was not toxic for tissue cells, thus making the chimeric phosphonate strategy a valid approach for the development of anti HIV-1 compound heterodimers.

Design, Synthesis, and Antiviral Evaluation of Chimeric Inhibitors of HIV Reverse Transcriptase

In a continuing study of potent bifunctional anti-HIV agents, we rationally designed a novel chimeric inhibitor utilizing thymidine (THY) and a TMC derivative (a diarylpyrimidine NNRTI) linked via a polymethylene linker (ALK). The nucleoside, 5'-hydrogen-phosphonate (H-phosphonate), and 5'-triphosphate forms of this chimeric inhibitor (THY-ALK-TMC) were synthesized and the antiviral activity profiles were evaluated at the enzyme and cellular level. The nucleoside triphosphate (11) and the H-phosphonate (10) derivatives inhibited RT polymerization with an IC50 value of 6.0 and 4.3 nM, respectively. Additionally, chimeric nucleoside (9) and H-phosphonate (10) derivatives reduced HIV replication in a cell-based assay with low nanomolar antiviral potencies.

Synthesis, biological evaluation and molecular docking studies of some pyrimidine derivatives

Some novel pyrimidine-5-carbonitrile derivatives bearing various substituent have been synthesized. The structures of target compounds were confirmed by elemental analysis and spectral data. Some selected members of the newly synthesized compounds were investigated for their cytotoxic potency against certain human tumor cell lines. Five representative active anticancer compounds 6a, 6c, 6d, 17a and 18a were subjected to docking using MOE program on the 3D structure of two enzymes, namely; thymidylate synthase and dihydrofolate reductase. The antimicrobial activities of the synthesized compounds were tested against Staphylococcus aureus, Pseudomonas aeruginosa, Shigella flexneri and Candida albicans. Compounds 2c, 7a and 9c showed broad spectrum antimicrobial activity.

Bifunctional inhibition of human immunodeficiency virus type 1 reverse transcriptase: mechanism and proof-of-concept as a novel therapeutic design strategy

Human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) is a major target for currently approved anti-HIV drugs. These drugs are divided into two classes: nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs and NNRTIs). This study illustrates the synthesis and biochemical evaluation of a novel bifunctional RT inhibitor utilizing d4T (NRTI) and a TMC-derivative (a diarylpyrimidine NNRTI) linked via a poly(ethylene glycol) (PEG) linker. HIV-1 RT successfully incorporates the triphosphate of d4T-4PEG-TMC bifunctional inhibitor in a base-specific manner. Moreover, this inhibitor demonstrates low nanomolar potency that has 4.3-fold and 4300-fold enhancement of polymerization inhibition in vitro relative to the parent TMC-derivative and d4T, respectively. This study serves as a proof-of-concept for the development and optimization of bifunctional RT inhibitors as potent inhibitors of HIV-1 viral replication.

Bifunctional inhibition of HIV-1 reverse transcriptase: a first step in designing a bifunctional triphosphate

The onset of resistance to approved anti-AIDS drugs by HIV necessitates the search for novel inhibitors of HIV-1 reverse transcriptase (RT). Developing single molecular agents concurrently occupying the nucleoside and nonnucleoside binding sites in RT is an intriguing idea but the proof of concept has so far been elusive. As a first step, we describe molecular modeling to guide focused chemical syntheses of conjugates having nucleoside (d4T) and nonnucleoside (TIBO) moieties tethered by a flexible polyethylene glycol (PEG) linker. A triphosphate of d4T-6PEG-TIBO conjugate was successfully synthesized that is recognized as a substrate by HIV-1 RT and incorporated into a double-stranded DNA.

HIV-1 NNRTIs: structural diversity, pharmacophore similarity, and implications for drug design

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) nowadays represent very potent and most promising anti-AIDS agents that specifically target the HIV-1 reverse transcriptase (RT). However, the effectiveness of NNRTI drugs can be hampered by rapid emergence of drug-resistant viruses and severe side effects upon long-term use. Therefore, there is an urgent need to develop novel, highly potent NNRTIs with broad spectrum antiviral activity and improved pharmacokinetic properties, and more efficient strategies that facilitate and shorten the drug discovery process would be extremely beneficial. Fortunately, the structural diversity of NNRTIs provided a wide space for novel lead discovery, and the pharmacophore similarity of NNRTIs gave valuable hints for lead discovery and optimization. More importantly, with the continued efforts in the development of computational tools and increased crystallographic information on RT/NNRTI complexes, structure-based approaches using a combination of traditional medicinal chemistry, structural biology, and computational chemistry are being used increasingly in the design of NNRTIs. First, this review covers two decades of research and development for various NNRTI families based on their chemical scaffolds, and then describes the structural similarity of NNRTIs. We have attempted to assemble a comprehensive overview of the general approaches in NNRTI lead discovery and optimization reported in the literature during the last decade. The successful applications of medicinal chemistry strategies, crystallography, and computational tools for designing novel NNRTIs are highlighted. Future directions for research are also outlined.

[d4U]-spacer-[HI-236] double-drug inhibitors of HIV-1 reverse-transcriptase

Four double-drug HIV NRTI/NNRTI inhibitors 15a-d of the type [d4U]-spacer-[HI-236] in which the spacer is varied as 1-butynyl (15a), propargyl-1-PEG (15b), propargyl-2-PEG (15c) and propargyl-4-PEG (15d) have been synthesized and biologically evaluated as RT inhibitors against HIV-1. The key step in their synthesis involved a Sonogashira coupling of 5-iodo d4U's benzoate with an alkynylated tethered HI-236 precursor followed by introduction of the HI-236 thiourea functionality. Biological evaluation in both cell-culture (MT-2 cells) as well as using an in vitro RT assay revealed 15a-c to be all more active than d4T. However, overall the results indicate the derivatives are acting as chain-extended NNRTIs in which for 15b-d the nucleoside component is likely situated outside of the pocket but with no evidence for any synergistic double binding between the NRTI and NNRTI sites. This is attributed, in part, to the lack of phosphorylation of the nucleoside component of the double-drug as a result of kinase recognition failure, which is not improved upon with the phosphoramidate of 15d incorporating a 4-PEG spacer.

Symmetrical and unsymmetrical alpha,omega-nucleobase amide-conjugated systems

We present the synthesis and selected physicochemical properties of several novel symmetrical and unsymmetrical alpha,omega-nucleobase mono- and bis-amide conjugated systems containing aliphatic, aromatic or saccharidic linkages. The final stage of the synthesis involves condensation of a subunit bearing carboxylic group with an amine subunit. 4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) was found to be a particularly effective condensing agent. The subunits containing carboxylic groups were obtained by acidic hydrolysis of N-1 Michael adducts of uracils or N-9 Michael adducts of 6-chloropurine with methyl acrylate. The amines used were aliphatic/aromatic diamines, adenine, 5-substituted 1-(ω-aminoalkyl)uracils and 5'-amino-2',5'-dideoxythymidine. The title compounds may find application as antiprotozoal agents. Moreover, preliminary microscopy TEM studies of supramolecular behaviour showed that target molecules with bolaamphiphilic structures were capable of forming highly ordered assemblies, mainly nanofibres.

Novel acyclic amide-conjugated nucleosides and their analogues

An effective one-step synthesis of new amide-conjugated nucleosides and their analogues, in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) as the condensing agent, is presented. Substrate subunits carrying carboxylic group were obtained by acidic hydrolysis of Michael-type adducts of various 5-substituted uracil derivatives to methyl acrylate. Amine substrate was synthesized by reduction of 1-(2'-cyanoethyl)thymine with sodium borohydride in the presence of nickel (II) chloride as catalyst. Other applied amine substrates were 5'-amino-5'-deoxythymidine and 5-aminouracil.

C-2-aryl O-substituted HI-236 derivatives as non-nucleoside HIV-1 reverse-transcriptase inhibitors

Several novel thiourea derivatives of the NNRTI HI-236 substituted at the C-2 oxygen of the phenyl ring have been synthesized and evaluated for their inhibitory activity against HIV-1 (IIIB) replication in MT-2 cell cultures. The compounds were synthesized in order to fine-tune the activity of HI-236 as well as to gain insight into spatial characteristics in the pocket pertaining to the positional choice of tether in the design of [NRTI]-tether-[HI-236] bifunctional inhibitors. Two of the thiourea derivatives bearing a butynyl (6c) or hydroxyethyl tether (6n) were endowed with improved anti-HIV activity compared to HI-236. NNRTI activity was confirmed by a cell-free RT assay on six of the derivatives in which 6c returned an IC(50) of 3.8 nM compared to 28 nM for HI-236, establishing it as an improved lead for HI-236. The structure-activity profile is discussed in terms of potential interactions in the NNRTI pocket as suggested by a docking model using AutoDock, which have a bearing on the bifunctional drug design.

Studies on the inhibition of Moloney murine leukemia virus reverse transcriptase by N-tritylamino acids and N-tritylamino acid-nucleotide compounds

N-Acylated derivatives of 8-(6-aminohexyl) amino-adenosine-5 '-phosphate were prepared and studied with regard to their effect on DNA synthesis by the Moloney leukemia virus reverse transcriptase. N-palmitoyl and N-nicotinyl derivatives and bis-8-(6-aminohexyl) amino-5'-AMP inhibited the enzyme partially using poly (rA).oligo d(pT)(16-18) as template-primer with [(3)H]dTTP. In order to increase hydrophobicity in the acyl component tethered to the 8-(6-aminohexyl) amino group on the adenine nucleotide, N-trityl-L-phenylalanine and the N-trityl derivatives of the o, m, and p-fluoro-DL-phenylalanine were initially examined for inhibition of the enzyme using the above template-primer system. The compounds all inhibited the reverse transcriptase with IC(50) values of approximately 60-80 microM. However, when N-trityl-m-fluoro-DL-phenylalanine was coupled to the nucleotide 8-(6-aminohexyl) amino-adenosine-5'-phosphate, the inhibitory activity of this compound increased significantly (IC(50) = 5 microM).

Fluorous 2,4-Dichloro-1,3,5-triazines (F-DCTs) as Nucleophile Scavengers

1H,1H,2H,2H,3H,3H‐perfluoroundecanol‐ and 1H,1H,2H,2H‐perfluorodecanethiol‐displaced 2,4‐dichloro‐1,3,5‐triazines 1 and 2 are synthesized and used as nucleophile scavengers to remove thiols and amines from solution‐phase reactions. Two active sites on the triazine ring are able to remove two equivalents of nucleophiles. The purification of reaction mixtures is accomplished by plate‐to‐plate fluorous solid‐phase extraction or automated solid‐phase extraction on the RapidTrace system.

Fluorous 2,4-Dichloro-1,3,5-triazine (F-DCT) as Amide Coupling Agent

1H,1H,2H,2H,3H,3H‐perfluoroundecanol displaced 2,4‐dichloro‐1,3,5‐triazine 5 is synthesized and used as a condensation agent for amide synthesis. Two active sites on the triazine ring lead to formation of two equivalents of amidation products. The purification of reaction mixtures is accomplished by plate‐to‐plate fluorous solid‐phase extraction.

Antiviral activity of 4-benzyl pyridinone derivatives as HIV-1 reverse transcriptase inhibitors

In this overview, the antiviral properties of the Curie-pyridinone compounds, a new class of non-nucleoside reverse transcriptase inhibitors (NNRTIs) developed as anti-HIV agents, are described. These compounds are hybrids between hydroxyethoxymethyl-phenylthiothymine (HEPT) and Merck pyridinones. Several structure-activity relationships (SAR) studies between HIV-1 reverse transcriptase (RT) and the Curie-pyridinones are described. The Curie-pyridinones are potent inhibitors of both HIV-1 replication in cell culture and of HIV-1 RT activity in vitro. They are specific to HIV-1 and do not inhibit the replication of HIV-2. The mechanism of inhibition is non-competitive with respect to the natural substrate dGTP. For these reasons, the Curie-pyridinones can be considered as non-nucleoside inhibitors of HIV-1 RT. Moreover, they have the unusual ability to reach the reverse transcription complex inside the extracellular virions and may therefore be useful as retrovirucides. This might lead to the design and synthesis of new drugs able to interact with the retroviral enzyme inside the viral core.

Synthesis and anti-HIV activity of [d4U]-[trovirdine analogue] and [d4T]-[trovirdine analogue] heterodimers as inhibitors of HIV-1 reverse transcriptase

A series of eleven heterodimers containing both a nucleoside analogue (d4U, d4T) and a non-nucleoside type inhibitor (Trovirdine analogue) were synthesized and evaluated for their ability to inhibit HIV replication. Unfortunately, the (N-3)d4U-Trovirdine conjugates (9a-e) and (N-3)d4T-Trovirdine conjugates (10a-f) were found to be inactive suggesting that the two individual inhibitor compounds do not bind simultaneously in their respective sites.