Potential anti-HIV Agents Research Articles

Synthesis of a cholesteryl-HEG phosphoramidite derivative and its application to lipid-conjugates of the anti-HIV 5'TGGGAG³' Hotoda's sequence.

A novel phosphoramidite derivative of cholesterol, with an ether-linked hexaethylene glycol (HEG) spacer arm, has been obtained through simple and reproducible solid phase modified oligonucleotide synthesis manipulations. This building block and the known phosphoramidite derivative of 3β-(2-hydroxyethoxy)cholesterol have been exploited in standard oligonucleotide synthesis protocols for the preparation of 5'- conjugates of the G-quadruplex-forming 5'TGGGAG3' oligomer, known as the Hotoda’s sequence, to produce new potential anti-HIV agents.

Enantioselective Total Synthesis of (+)-Lithospermic Acid

An enantioselective synthesis of (+)-lithospermic acid, a potent anti-HIV agent, has been accomplished in a convergent manner in nine steps. The synthesis features an enantioselective intramolecular oxa-Michael addition catalyzed by a quinidine derivative, a hypervalent iodine-mediated rearrangement of chromanone to dihydrobenzofuran, an enantioselective α-oxyamination, and an intermolecular C-H olefination.

Structure–activity relationship study of pyrimido[1,2-c][1,3]benzothiazin-6-imine derivatives for potent anti-HIV agents

3,4-Dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (PD 404182) is an antiretroviral agent with submicromolar inhibitory activity against human immunodeficiency virus-1 (HIV-1) and HIV-2 infection. In the current study, the structure–activity relationships of accessory groups at the 3- and 9-positions of pyrimido[1,2-c][1,3]benzothiazin-6-imine were investigated for the development of more potent anti-HIV agents. Several different derivatives containing a 9-aryl group were designed and synthesized using Suzuki–Miyaura cross-coupling and Ullmann coupling reactions. Modification of the m-methoxyphenyl or benzo[d][1,3]dioxol-5-yl group resulted in improved anti-HIV activity. In addition, the 2,4-diazaspiro[5.5]undec-2-ene-fused benzo[e][1,3]thiazine derivatives were designed and tested for their anti-HIV activities. The most potent 9-(benzo[d][1,3]dioxol-5-yl) derivative was two–threefold more effective against several strains of HIV-1 and HIV-2 than the parent compound, PD 404182.

Synthesis and Conformation of Novel 3'-Branched Threosyl-5'-Deoxyphosphonic Acid Nucleoside Analogues

The discovery that threosyl phosphonate nucleoside (PMDTA, <TEX>$EC_{50}=2.53{\mu}M$</TEX>) is a potent anti-HIV agent has led to the synthesis and biological evaluation of 5'-deoxy versions of threosyl phosphonate nucleosides. In the present study, (E)-3'-phosphonoalkenyl and 3'-phosphonoalkyl nucleoside analogues 13, 16, 20 and 23 were synthesized from acetol and tested for anti-HIV activity and cytotoxicity. The adenine analogue 16 was found to exhibit moderate in vitro anti-HIV-1 activity (<TEX>$EC_{50}=22.2{\mu}M$</TEX>).

Molecular dynamics simulations of UC781-cyclodextrins inclusion complexes in aqueous solution

The inclusion complexes of highly potent anti-HIV agent, UC781, with β-cyclodextrin (βCD), 2,6-dimethyl-β-cyclodextrin (MβCD), and 2-hydroxypropyl-β-cyclodextrin (HPβCD) in aqueous solution were investigated by molecular dynamics simulations. Simulations show that the phenyl ring of UC781 is trapped inside CD cavities, while the NH group of UC781 interacts with secondary hydroxyl groups at the wider rim of CDs. The different types of CDs directly affect the binding energy and the stability of the inclusion complexes. MβCD provides the most stable inclusion complex of UC781 among all CDs in this study due to the effect of methoxy groups (–OCH3) at C2 and C6 positions on the glucopyranose of CDs. Structure analysis of CDs and the orientation of UC781 inside CD cavities as well as the effects of aqueous solution to the inclusion complexes of UC781/CDs are discussed. Results of this study have provided an agreeable output; therefore, a reliable prediction method for other drug/CD inclusion complex formations is introduced.

Design and Synthesis of Novel Threosyl-5′- Deoxyphosphonic Acid Purine Analogues as Potent Anti-Hiv Agents

The discovery of threosyl phosphonate nucleoside (PMDTA, EC50 = 2.53 μM) as a potent anti-HIV agent has led to the synthesis and biological evaluation of 5 ′-deoxyversions of threosyl phosphonate nucleosides from 1,4-dihydroxy-2-butene. The synthesized nucleoside phosphonic acid analogues 14 and 19 were tested for anti-HIV activity as well as cytotoxicity. The adenine analogue 14 exhibits moderate in vitro anti-HIV-1 activity (EC50 = 12.6 μM).

Synthesis, Anti‐HIV Activity Studies, and in silico Rationalization of Cyclobutane‐Fused Nucleosides

The present work describes some recent approaches to novel 3-oxabicyclo[3.2.0]heptane-type nucleosides structurally similar to the potent anti-HIV agent stavudine (d4T). To gain knowledge at the molecular level relevant for further synthetic designs, the lack of activity of these compounds was investigated by computational approaches accounting for three main physiological requirements of anti-HIV nucleosides: their drug-likeness, their activation process, and their subsequent interaction with HIV reverse transcriptase (HIV-RT). Our results show that the inclusion of the fused cyclobutane at the 2'- and 3'-positions of the sugar portion provides drug-like compounds. Nonetheless, the presence of this cyclobutane moiety prevents binding orientations consistent with the catalytic activation for at least one of the enzymes known to activate d4T. To the best of our knowledge, this is the first study to explicitly consider the simulation of the entire activation process to rationalize anti-HIV activities.

Treatment of Halogen Bonding in the OPLS-AA Force Field: Application to Potent Anti-HIV Agents

The representation of chlorine, bromine, and iodine in aryl halides has been modified in the OPLS-AA and OPLS/CM1A force fields in order to incorporate halogen bonding. The enhanced force fields, OPLS-AAx and OPLS/CM1Ax, have been tested in calculations on gas-phase complexes of halobenzenes with Lewis bases, and for free energies of hydration, densities, and heats of vaporization of halobenzenes. Comparisons with results of MP2/aug-cc-pVDZ(-PP) calculations for the complexes are included. Implementation in the MCPRO software also allowed computation of relative free energies of binding for a series of HIV reverse transcriptase inhibitors via Monte Carlo/free-energy perturbation calculations. The results support the notion that the activity of an unusually potent chloro analog likely benefits from halogen bonding with the carbonyl group of a proline residue.

Phosphoramidate Prodrugs of (−)-β-D-(2R,4R)-dioxolane-thymine (DOT) as Potent Anti-HIV Agents

Nucleoside reverse transcriptase inhibitors (NRTIs) are an effective class of agents that has played a vital role in the treatment of HIV infections. (-)-β-D-(2R,4R)-dioxolane-thymine (DOT) is a thymidine analogue that is active against wild-type and NRTI-resistant HIV-1 mutants. It has been shown that the anti-HIV activity of DOT is limited due to poor monophosphorylation. To further enhance the anti-HIV activity of DOT, an extensive structure-activity relationship analysis of phosphoramidate prodrugs of DOT monophosphate was undertaken. These prodrugs were evaluated for anti-HIV activity using Hela CD4 β-gal reporter cells (P4-CCR5 luc cells). Among the synthesized prodrugs, the 4-bromophenyl benzyloxy l-alanyl phosphate derivative of DOT was the most potent, with a 50% effective concentration of 0.089 μM corresponding to a 75-fold increase in activity relative to the parent nucleoside DOT with no increased cytotoxicity. The metabolic stability of a selected number of potent DOT phosphoramidates was also evaluated in simulated gastric fluid, simulated intestinal fluid, human plasma and liver S9 fractions. A series of new phosphoramidate prodrugs of DOT were prepared and evaluated as inhibitors of HIV replication in vitro. Metabolic stability studies indicated that these DOT phosphoramidate derivatives have the potential to show acceptable stability in the gastrointestinal tract, but they metabolize rapidly in the liver.

Hydroxyl may not be indispensable for raltegravir: Design, synthesis and SAR Studies of raltegravir derivatives as HIV-1 inhibitors

A series of raltegravir derivatives 20–42 were prepared and systematically evaluated for their anti-HIV activity. The bioassay results showed that most of the compounds possess good to excellent anti-HIV activity. Especially, compounds 25 and 35 with subpicomole IC50 values seemed to be the most potent anti-HIV agents among all of the reported synthesized compounds. These compounds may therefore be considered as new potent anti-HIV agents. The 5-hydroxyl modification of raltegravir derivatives significantly increased the anti-HIV activity, which indicates that the hydroxyl may not be indispensable for raltegravir. The introducing of acyl at 5-position of raltegravir derivatives is favorable for antiviral activity. In addition, a high-throughput cell-based assay method with pseudotyped virus stocks was developed and used to identify HIV inhibitors.

A ligand-based approach for the in silico discovery of multi-target inhibitors for proteins associated with HIV infection

Acquired immunodeficiency syndrome (AIDS) is a dangerous disease, which damages the immune system cells to the point that the immune system can no longer fight against other infections that it would usually be able to prevent. The causal agent is the human immunodeficiency virus (HIV), and for this reason, the search for more effective chemotherapies against HIV is a challenge for the scientific community. Chemoinformatics and Quantitative Structure-Activity Relationship (QSAR) studies have played an essential role in the design of potent inhibitors for proteins associated with the HIV infection. However, all previous studies took into consideration the discovery of future drug candidates using homogeneous series of compounds against only one protein. This fact limits the use of more efficient anti-HIV chemotherapies. In this work, we develop the first ligand-based approach for the in silico design of multi-target (mt) inhibitors for seven key proteins associated with the HIV infection. Two mt-QSAR models were constructed from a large and heterogeneous database of compounds. The first model was based on linear discriminant analysis (mt-QSAR-LDA) employing fragment-based descriptors. The second model was obtained using artificial neural networks (mt-QSAR-ANN) with global 2D descriptors. Both models correctly classified more than 90% of active and inactive compounds in training and prediction sets. Some fragments were extracted and their contributions to anti-HIV activity through inhibition of the different proteins were calculated using the mt-QSAR-LDA model. New molecules designed from fragments with positive contributions were suggested and correctly predicted by the two models as possible potent and versatile anti-HIV agents.

First Synthesis of [6-15N]-Cladribine Using Ribonucleoside as a Starting Material

We have synthesized two types of [6-N]-deoxyadenosine analogs: [6-N]-2′-deoxyadenosine (1) and [6-N]-2-chloro-2′-deoxyadenosine ([6-N]-cladribine, 2), which utilized the readily available ribonucleosides inosine and guanosine, respectively, via 3′-benzoyl-5′-trityl(or tert-butyldimethylsilyl)-substituted intermediates (6, 15). N-labelled adenosine derivatives can be applicable to a variety of intended purposes. Practically speaking, many of the [N]-nitrogen-stable isotope-labeled nucleosides are synthetic building blocks of N-labelled oligonucleotides, which are more commonly utilized as probes that help clarify the structure of nucleic acids, the mechanism of drug binding, and the interactions between proteins and nucleosides by the use of H-NMR spectra, N-NMR spectra, or both. In particular, [6-N]-2′-deoxyadenosine (1) was synthesized relatively early once this nucleoside analog started to attract attention as a probe material. Jones et al. reported a synthetic process of this labeled compound in which deoxyadenosine was enzymatically deaminated to give deoxyinosine, which was then di-acetylated at the 3′and 5′-hydroxy groups, and then O-sulfonylation, followed by [N]-benzylamination at the 6-position of the adenine skeleton, following oxidation with ruthenium oxide. In addition, Kelly and co-workers have synthesized [6-N]-deoxyadenosine (1) in two steps from commercially available starting material, 6-chloropurine using the enzymatic transglycosylation method. Their approach has allowed for the simple and straightforward construction of large quantities of this material. While Maruyama et al. in our laboratory synthesized an effectively potent anti-HIV agent, FddA, using a 6-chloropurine riboside analog as a starting material via the conversion of selective 3′-benzoylation, 2′-fluorination, and 3′-deoxygenation in the sugar moiety. In this study, we adapted Maruyama’s approach to develop an alternative synthetic route to [6-N]-2′-deoxyadenosine (1) from the readily available and economical ribonucleoside inosine, using it as the starting substance. HETEROCYCLES, Vol. 85, No. 1, 2012 171

Large-scale Synthesis of GMP Grade N'-[2-(2-Thiophene)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea (HI-443), a New Anti-HIV Drug Candidate

The thiourea compound N'-[2-(2-thiophene)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea (HI-443, CAS 258340-15-7), was found to be a potent anti-HIV agent with remarkable activity against nucleoside analog reverse transcriptase (NRT)-resistant, non-nucleoside analog reverse transcriptase (NNRT)-resistant, as well as multidrug-resistant HIV. Now the method of producing HI-443 under current Good Manufacturing Practice (cGMP) conditions on the scale of kilograms is reported. The availability of GMP-grade HI-443 will promote the preclinical and clinical development efforts aimed at making this new drug candidate available to HIV-infected persons.

Computationally-Guided Optimization of a Docking Hit to Yield Catechol Diethers as Potent Anti-HIV Agents

A 5-μM docking hit has been optimized to an extraordinarily potent (55 pM) non-nucleoside inhibitor of HIV reverse transcriptase. Use of free energy perturbation (FEP) calculations to predict relative free energies of binding aided the optimizations by identifying optimal substitution patterns for phenyl rings and a linker. The most potent resultant catechol diethers feature terminal uracil and cyanovinylphenyl groups. A halogen bond with Pro95 likely contributes to the extreme potency of compound 42. In addition, several examples are provided illustrating failures of attempted grafting of a substructure from a very active compound onto a seemingly related scaffold to improve its activity.

Synthesis of Novel 6′-Spirocyclopropyl-5′-Norcarbocyclic Adenosine Phosphonic Acid Analogues as Potent Anti-Hiv Agents

Novel 5′-norcarbocyclic adenosine phosphonic acid analogues with 6′-electropositive moiety such as spirocyclopropane were designed and synthesized from the commercially available diethylmalonate 5. Regioselective Mitsunobu reaction proceeded in the presence of an allylic functional group at a low reaction temperature in polar cosolvent [dimethylformamide (DMF)/1,4-dioxane] to give purine analogue 15. To improve cellular permeability and enhance the anti-human immunodeficiency virus (HIV) activity of this phosphonic acid, a SATE phosphonodiester nucleoside prodrug 23 was prepared. The synthesized adenosine phosphonic acids analogues 18–21 and 23 were subjected to antiviral screening against HIV-1.

Design and Synthesis of Carbocyclic Versions of Furanoid Nucleoside Phosphonic Acid Analogues as Potential Anti-Hiv Agents

Novel 5′-norcarbocyclic adenine and guanine phosphonic acid analogues with 6′,6′-difluorine moiety were designed and synthesized from commercially available epichlorohydrin 5. A regioselective Mitsunobu reaction successfully proceeded from an allylic functional group 16b at low reaction temperature in polar cosolvent to give purine phosphonate analogues 17 and 24, respectively. The purine nucleoside phosphonate and phosphonic acid analogues were subjected to antiviral screening against HIV-1. Adenine analogue 21 and its SATE prodrug 29 show significant anti-HIV activity in MT-4 cell lines.

Efficient discovery of potent anti-HIV agents targeting the Tyr181Cys variant of HIV reverse transcriptase.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) that interfere with the replication of human immunodeficiency virus (HIV) are being pursued with guidance from molecular modeling including free-energy perturbation (FEP) calculations for protein-inhibitor binding affinities. The previously reported pyrimidinylphenylamine 1 and its chloro analogue 2 are potent anti-HIV agents; they inhibit replication of wild-type HIV-1 in infected human T-cells with EC(50) values of 2 and 10 nM, respectively. However, they show no activity against viral strains containing the Tyr181Cys (Y181C) mutation in HIV-RT. Modeling indicates that the problem is likely associated with extensive interaction between the dimethylallyloxy substituent and Tyr181. As an alternative, a phenoxy group is computed to be oriented in a manner diminishing the contact with Tyr181. However, this replacement leads to a roughly 1000-fold loss of activity for 3 (2.5 μM). The present report details the efficient, computationally driven evolution of 3 to novel NNRTIs with sub-10 nM potency toward both wild-type HIV-1 and Y181C-containing variants. The critical contributors were FEP substituent scans for the phenoxy and pyrimidine rings and recognition of potential benefits of addition of a cyanovinyl group to the phenoxy ring.

Enantioselective Total Synthesis of the Potent Anti-HIV Nucleoside EFdA

A concise enantioselective total synthesis of 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA), an extremely potent anti-HIV agent, has been accomplished from (R)-glyceraldehyde acetonide in 18% overall yield by a 12-step sequence involving a highly diastereoselective ethynylation of an α-alkoxy ketone intermediate.

Analogues of a lupane-type triterpene as potential anti-HIV agents

Infection with human immunodeficiency virus (HIV), the etiologic agent of acquired immunodeficiency syndrome (AIDS), continues to be ranked high on the list of the most important health issues facing the world. Although significant progress has been made since the introduction of highly active antiretroviral therapy, it has also led to increased adverse effects and the emergence of multidrug-resistant viral strains. Therefore, there is a need for new classes of drugs involving novel molecular mechanisms [1].

Synthesis of new 2′-deoxy-2′-fluoro-4′-azido nucleoside analogues as potent anti-HIV agents

We prepared 1-(4′-azido-2′-deoxy-2′-fluoro- β- d-arabinofuranosyl)cytosine ( 10) and its hydrochloride salt ( 11) as potential antiviral agents based on the favorable antiviral profiles of 4′-substituted nucleosides. Compounds 10 and 11 were synthesized from 1,3,5- O-tribenzoyl-2-deoxy-2-fluoro- d-arabinofuranoside in multiple steps, and their structures were unequivocally established by IR, 1H NMR, 13C NMR, and 19F NMR spectroscopy, HRMS, and X-ray crystallography. Compounds 10 and 11 exhibited potent anti-HIV-1 activity (EC 50: 0.3 and 0.13 nM, respectively) without significant cytotoxicity in concentrations up to 100 μM. Compound 11 exhibited extremely potent anti-HIV activity against NL4-3 (wild-type), NL4-3 (K101E), and RTMDR viral strains, with EC 50 values of 0.086, 0.15, and 0.11 nM, respectively. Due to the high potency of 11, it was also screened against an NIH Reagent Program NRTI-resistant virus panel containing eleven mutated viral strains and for cytotoxicity against six different human cell lines. The results of this screening indicated that 11 is a novel NRTI that could be developed as an anti-AIDS clinical trial candidate to overcome drug-resistance issues.