Anti-AIDS agents 88. Anti-HIV conjugates of betulin and betulinic acid with AZT prepared via click chemistry

In the present study, a new strategy to link AZT with betulin/betulinic acid (BA) by click chemistry was designed and achieved. This conjugation via a triazole linkage offers a new direction for modification of anti-HIV triterpenes. Click chemistry provides an easy and productive way for linking two molecules, even when one of them is a large natural product. Among the newly synthesized conjugates, compounds 15 and 16 showed potent anti-HIV activity with EC(50) values of 0.067 and 0.10 μM, respectively, which are comparable to that of AZT (EC(50): 0.10 μM) in the same assay.     

Synthesis and biological evaluation of 5′-O-dicarboxylic fatty acyl monoester derivatives of anti-HIV nucleoside reverse transcriptase inhibitors

A number of 5′-O-dicarboxylic fatty acyl monoester derivatives of 3′-azido-3′-deoxythymidine (zidovudine, AZT), 2′,3′-didehydro-2′,3′-dideoxythymidine (stavudine, d4T), and 3′-fluoro-3′-deoxythymidine (alovudine, FLT) were synthesized to improve the lipophilicity and potentially the cellular delivery of parent polar 2′,3′-dideoxynucleoside (ddN) analogs. The compounds were evaluated for their anti-HIV activity. Three different fatty acids with varying chain length of suberic acid (octanedioic acid), sebacic acid (decanedioic acid), and dodecanedioic acid were used for the conjugation with the nucleosides. The compounds were evaluated for anti-HIV activity and cytotoxicity. All dicarboxylic ester conjugates of nucleosides exhibited significantly higher anti-HIV activity than that of the corresponding parent nucleoside analogs. Among all the tested conjugates, 5′-O-suberate derivative of AZT (EC₅₀ = 0.10 nM) was found to be the most potent compound and showed 80-fold higher anti-HIV activity than AZT without any significant toxicity (TC₅₀ >500 nM).     

Anti‐AIDS active polyrotaxane‐AZT conjugates with bioactive bulky stoppers and their nanoparticles

New anti‐HIV active agents, polyrotaxane‐AZT conjugates with various bioactive bulky stoppers such as 3′‐azido‐3′‐deoxythymidine (AZT) and tocopherol and their nanoparticles were synthesized and characterized. The degree of AZT substitution of the conjugates was calculated from ELEM . ANAL and ranged from 1.8 to 5.9, respectively. The in vitro antiviral activity of these conjugates was determined and used to evaluate their potential applications in anti‐AIDS drugs. The in vitro anti‐HIV activities indicate that the synthesized polyrotaxane‐AZT conjugates and their nanoparticles against HIV‐1 and HIV‐2 strains were more potent inhibitors than free AZT, with reduced cytotoxicities against uninfected MT‐4 cells. The effect of the conjugates against HIV‐1 and HIV‐2 strains increased with decreasing particle size. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Neamine-heterocycle conjugates as potential anti-HIV agents

A series of neamine-heterocycle conjugates were designed and synthesized. All new compounds displayed more potent inhibitory effect on HIV replication than neamine, among them two compounds displayed stronger anti-HIV activity than neomycin B. The results suggested that itmight be a promising approach to modify neamine for the discovery of new anti-HIV agents.     

Synthesis of sulfated alkyl oligosaccharides with potent anti-HIV activity

Sulfated alkyl malto- and laminari-oligosaccharides with potent anti-human immunodeficiency virus (HIV) activities were synthesized. Present work focusses on the syntheses of high anti-HIV active compounds from low molecular weight carbohydrates which will react selectively with AIDS virus protein only. A surface-active agent type compound consisting of both hydrophilic sulfated oligosaccharide and hydrophobic alkyl group portion was prepared. Individual pure malto-oligosaccharides from malto-tetraose to -heptaose and laminarioligosaccharides from laminari-pentaose to -nonaose were used as the starting carbohydrates. Synthesis of peracetylated alkyl oligosaccharide was carried out with β-peracetylated oligosaccharides and corresponding alcohols by using Lewis acid catalysts. Sulfation was performed with sulfur trioxide-pyridine complex. The anti-HIV activity was assayed by means of MT-4 cells and HIV-1 or HIV-2 viruses. Almost all sulfated alkyl oligosaccharides exhibited potent inhibitory effects on HIV infection. Sulfated alkyl laminari-oligosaccharides which have various kind of aklyl portion such as fluoro alkyl, chiral alkyl, cyclic alkyl, and phenyl alkyl were also examined. In addition, this study also provides an assessment of activity levels of sulfated alkyl oligosaccharides in small mammals.     

Chemical modification of oleanene type triterpenes and their inhibitory activity against HIV-1 protease dimerization

Oleanolic acid derivatives with different lengths of 3-O-acidic acyl chains were synthesized and evaluated for their inhibitory activity against HIV-1 protease. The lengths of the acidic chains were optimized to 6 and 8 carbons. Changing a 3-ester bond to an amide bond or dimerization of the triterpenes retained their inhibitory activity against HIV-1 protease. Introduction of an additional acidic chain to C-28 of oleanolic acid increased the inhibitory activity appreciably, though a derivative with only one acidic chain linked at C-28 also showed potent activity against HIV-1 protease. The inhibitory mechanism was proved directly by size exclusion chromatography to be inhibition of dimerization of the enzyme polypeptides. The ester bonds of the triterpene derivatives were found to be stable to lipase under mild alkaline conditions.     

Computational Studies and Drug Design for HIV-1 Reverse Transcriptase Inhibitors of 3′,4′-di-O-(S)-camphanoyl-(+)-cis-Khellactone (DCK) Analogs

Molecular docking and molecular dynamics simulation were applied to study the binding mode of 3',4'-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) analogs anti-HIV inhibitors with HIV-1 RT. The results suggest that there is a strong hydrogen bond between DCK O16 and NH of Lys101, and that DCK analogues might act similarly as other types of HIV-1 RT inhibitors. The investigation about drug resistance for DCK shows no remarkable influence on the most frequently observed mutation K103N of HIV-1 RT. Based on the proposed mechanism, some new structures were designed and predicted by a SVM model. All compounds exhibited potent inhibitory activities against HIV replication in H9 lymphocytes with EC50 values lower than 1.95 microM. The rationality of the method was validated by experimental results.     

Stapled SC34EK fusion inhibitors with high potency against HIV-1 and improved protease resistance

A single all-hydrocarbon staple introduction in SC34EK can afford a potent HIV inhibitor with high protease resistance for ADIS treatment.     

Structure and anti-HIV activity of micrandilactones B and C, new nortriterpenoids possessing a unique skeleton from Schisandra micrantha

Two new highly oxygenated nortriterpenoids with a unique norcycloartane skeleton, micrandilactones B and C, were isolated from Schisandra micrantha; micrandilactone C exhibited an EC50 value of 7.71 microg/mL (SI > 25.94) against HIV-1 replication with minimal cytotoxicity, and the potent anti-HIV-1 activity and unique structural features of make it a promising lead for therapeutic development of a new generation of anti-HIV drug.     

Design and synthesis of novel camptothecin/5-fluorouracil conjugates as cytotoxic agents

In an effort to overcome several limitations associated with the synthesis of camptothecin (CPT), seven conjugates (10a-10g) composed of CPT and a 5-fluorouracil derivative joined by suitable dipeptide linkages were synthesised, and their cytotoxic activity against four human tumour cell lines as well as an in vitro pharmacokinetic determination of their lactone stability were studied. Among these compounds, most tested conjugates showed cytotoxic activities comparable or superior to CPT-11 (2), but they were less potent when compared with CPT (1). Interestingly, all of the compounds showed selective inhibitory activities against BGC-823, with IC?? values lower than 0.1 μmol, which is more potent than CPT-11 (2). Also, the in vitro pharmacokinetic determination of the lactone levels of the representative compound 10b showed that the biological life span of their lactone forms in human and mouse plasma were significantly increased when compared with their mother compound CPT (1).     

Molecular alteration in drug susceptibility against subtype B and C-SA HIV-1 proteases: MD study

Structural Chemistry - HIV-1 protease (HIV PR) is one of the most promising targets for anti-HIV drug discovery. Extensive anti-HIV drug discovery research was focused on HIV-1 subtype B protease...     

Structure-based linker optimization of 6-(2-cyclohexyl-1-alkyl)-2-(2-oxo-2-phenylethylsulfanyl)pyrimidin-4(3H)-ones as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

In continuation of our efforts toward the discovery of potent HIV-1 NNRTIs with diverse structures,a series of novel S-DACO analogues of 6-(2-cyclohexyl-1-allkyl)-2-(2-oxo-2-phenyl-ethylsulfanyl)pyrimidin-4(3 H)-ones were designed,synthesized and evaluated for their antiviral activities in MT-4 cells.Most of these new compounds showed moderate to good activities against wild type HIV-1 with IC_(50) values ranging from 7.55 μmol/L to 0.018 μmol/L.Among them,compound 5 c was identified as the most promising inhibitor against HIV-1 replication with an IC_(50)=0.018 μmol/L,CC_(50)=194 μmol/L,and SI=12791,which was much more potent than the reference drugs NVP and DLV and comparable to AZT and EFV.In addition,5 c also exhibited improved activity against double mutant HIV-1 strain RES056 compared to that of the reference drugs NVP/DLV and DB02.The preliminary structure-activity relationship(SAR) and molecular modeling studies were also discussed,which provides some useful indications for guiding the further rational design of new S-DACO analogues.     

Potent HIV-1 protease inhibitors incorporating meso-bicyclic urethanes as P2-ligands: structure-based design, synthesis, biological evaluation and protein-ligand X-ray studies

Recently, we designed a series of novel HIV-1 protease inhibitors incorporating a stereochemically defined bicyclic fused cyclopentyl (Cp-THF) urethane as the high affinity P2-ligand. Inhibitor with this P2-ligand has shown very impressive potency against multi-drug-resistant clinical isolates. Based upon the -bound HIV-1 protease X-ray structure, we have now designed and synthesized a number of meso-bicyclic ligands which can conceivably interact similarly to the Cp-THF ligand. The design of meso-ligands is quite attractive as they do not contain any stereocenters. Inhibitors incorporating urethanes of bicyclic-1,3-dioxolane and bicyclic-1,4-dioxane have shown potent enzyme inhibitory and antiviral activities. Inhibitor (K(i) = 0.11 nM; IC(50) = 3.8 nM) displayed very potent antiviral activity in this series. While inhibitor showed comparable enzyme inhibitory activity (K(i) = 0.18 nM) its antiviral activity (IC(50) = 170 nM) was significantly weaker than inhibitor . Inhibitor maintained an antiviral potency against a series of multi-drug resistant clinical isolates comparable to amprenavir. A protein-ligand X-ray structure of -bound HIV-1 protease revealed a number of key hydrogen bonding interactions at the S2-subsite. We have created an active model of inhibitor based upon this X-ray structure.     

Inhibition of influenza virus sialidase and anti-influenza virus activity by plant flavonoids

Flavonoids (103 species) were tested for inhibitory activity against influenza virus sialidase using sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate as substrate. 5,7,4'-Trihydroxy-8-methoxyflavone from the root of Scutellaria baicalensis showed the most potent activity (IC50, 55 microM), and this flavone appeared to be a non-competitive inhibitor of the enzyme. Whereas, negligible or weak inhibitory activities were observed for mouse liver sialidase, beta-galactosidase and alpha-mannosidase as tested. This flavone also inhibited the infection by influenza virus A/PR/8/34 of Madin-Darby canine kidney cells, and replication of the virus in the allantoic sack of embryonated egg. These results suggest that flavone, which has potent influenza virus sialidase inhibitory activity, may have anti-influenza virus activity.     

Synthesis and α-amylase inhibitory activity of glucose-deoxynojirimycin conjugates

Inhibitors of α-amylase have attracted attention for their putative effects against diabetes mellitus. Although numerous studies have explored natural small molecule inhibitors, acarbose is currently the only compound with sufficient inhibitory potency and drug-like characteristics to be considered as a potential therapeutic agent. We have synthesized conjugates of the potent glucosidase inhibitor, 1-deoxynojirimycin, and glucose, with the aim of enhancing inhibitory activity against α-amylase. This synthetic conjugate showed increased inhibition of α-amylase compared to 1-deoxynojirimycin alone, suggesting that similar modifications of existing glucosidase inhibitors may yield more potent α-amylase inhibitors.     

An insight to the molecular interactions of the FDA approved HIV PR drugs against L38L↑N↑L PR mutant

The aspartate protease of the human immune deficiency type-1 virus (HIV-1) has become a crucial antiviral target in which many useful antiretroviral inhibitors have been developed. However, it seems the emergence of new HIV-1 PR mutations enhances drug resistance, hence, the available FDA approved drugs show less activity towards the protease. A mutation and insertion designated L38L↑N↑L PR was recently reported from subtype of C-SA HIV-1. An integrated two-layered ONIOM (QM:MM) method was employed in this study to examine the binding affinities of the nine HIV PR inhibitors against this mutant. The computed binding free energies as well as experimental data revealed a reduced inhibitory activity towards the L38L↑N↑L PR in comparison with subtype C-SA HIV-1 PR. This observation suggests that the insertion and mutations significantly affect the binding affinities or characteristics of the HIV PIs and/or parent PR. The same trend for the computational binding free energies was observed for eight of the nine inhibitors with respect to the experimental binding free energies. The outcome of this study shows that ONIOM method can be used as a reliable computational approach to rationalize lead compounds against specific targets. The nature of the intermolecular interactions in terms of the host–guest hydrogen bond interactions is discussed using the atoms in molecules (AIM) analysis. Natural bond orbital analysis was also used to determine the extent of charge transfer between the QM region of the L38L↑N↑L PR enzyme and FDA approved drugs. AIM analysis showed that the interaction between the QM region of the L38L↑N↑L PR and FDA approved drugs are electrostatic dominant, the bond stability computed from the NBO analysis supports the results from the AIM application. Future studies will focus on the improvement of the computational model by considering explicit water molecules in the active pocket. We believe that this approach has the potential to provide information that will aid in the design of much improved HIV-1 PR antiviral drugs.