Through a structure-based molecular hybridization and bioisosterism approach, a series of novel 2-(pyridin-3-yloxy)acetamide derivatives were designed, synthesized, and evaluated for their anti-HIV activities in MT-4 cell cultures. Biological results showed that three compounds (Ia, Ih, and Ij) exhibited moderate inhibitory activities against wild-type (wt) HIV-1 strain (III_B) with EC₅₀ values ranging from 8.18 μm to 41.52 μm. Among them, Ij was the most active analogue possessing an EC₅₀ value of 8.18 μm. To further confirm the binding target, four compounds were selected to implement an HIV-1 RT inhibitory assay. In addition, preliminary structure–activity relationship (SAR) analysis and some predicted physicochemical properties of three active compounds Ia, Ih, and Ij were discussed in detail. Molecular docking studies were also carried out to investigate the binding modes of Ij and the lead compound GW678248 in the binding pocket of RT, which provided beneficial information for further rational design of non-nucleoside reverse transcriptase inhibitors.

With the continuation of our unremitting efforts toward the discovery of potent HIV-1 NNRTIs, a series of novel imidazo[4,5-b]pyridin-2-ylthioacetanilides were designed, synthesized, and evaluated for their antiviral activities through combining bioisosteric replacement and structure-based drug design. Almost all of the title compounds displayed moderate to good activities against wild-type (wt) HIV-1 strain with EC₅₀ values ranging from 0.059 to 1.41 μm in a cell-based antiviral assay. Thereinto, compounds 12 and 13 were the most active two analogues possessing an EC₅₀ value of 0.059 and 0.073 μm against wt HIV-1, respectively, which was much more effective than the control drug nevirapine (EC₅₀ = 0.26 μm) and comparable to delavirdine (EC₅₀ = 0.038 μm). In addition, one selected compound showed a remarkable reverse transcriptase inhibitory activity compared to nevirapine and etravirine. In the end of this manuscript, preliminary structure–activity relationships (SARs) and molecular modeling studies were detailedly discussed, which may provide valuable insights for further optimization.

A series of novel 5-alkyl-6-Adamantylmethylpyrimidin-4(3H)-ones bearing various substituents at the C-2 position of the pyrimidinone ring were synthesized using a facile route and evaluated for their anti-HIV activity in MT-4 cells. The biological results demonstrated that the majority of the newly designed compounds possessed moderate efficiency in inhibiting the replication of the wild-type (WT) HIV-1 strain (III_B) with EC₅₀ values in the range from 0.10 to 5.39 μm. Among them, 5b1 and 5b3 proved to be the two most active inhibitors against WT HIV-1 with EC₅₀ values of 0.10 and 0.12 μm, respectively, which were more active than nevirapine (NVP) in the same assay. In addition, HIV-1 reverse-transcriptase (RT) inhibition assay indicated that the representative compound 5b1 showed affinity to WT HIV-1 RT, and inhibited the activity of RT with an IC₅₀ value superior to the reference drug NVP. Moreover, the preliminary structure–activity relationship (SAR) and the molecular modeling analysis of these new derivatives are also discussed.

Based on the hybridization of the privileged fragments in DABO and DAPY-typed HIV-1 NNRTIs, a novel series of 4-aminopiperidinyl-linked 3,5-disubstituted-1,2,6-thiadiazine-1,1-dione derivatives were designed, synthesized, and evaluated for their in vitro anti-HIV activities in MT-4 cells. Most of the target compounds showed weak inhibitory activity against WT HIV-1. In order to confirm the mode of action of the target compounds, representative compounds Ba8 and Bb8 were selected to perform the HIV-1 RT inhibitory assay. In this assay, Ba8 and Bb8 displayed good activity with IC₅₀ values of 3.15 and 1.52 μm, respectively. Additionally, preliminary structure–activity relationships (SARs) analysis and molecular docking studies of newly synthesized compounds are also discussed.

A series of benzoyl diarylamine/ether derivatives were designed, synthesized, and evaluated for their activity against human immunodeficiency virus (HIV) in MT-4 cells. Three compounds (3b, 5a, and 6a1) exhibited moderate activities against wild-type (wt) HIV-1 with EC₅₀ values ranging from 11 to 56 μm. Among them, compound 5a was the most potent inhibitor with a novel chemical skeleton, affording a new lead compound for further molecular optimization. An enzyme assay was also implemented to confirm the binding target of the active compounds represented by 6a1. Molecular simulation studies on compound 5a, 6a1, and 7a4 were carried out to understand their binding mode with wt HIV-1 reverse transcriptase (RT) and provided useful information for further rational design of NNRTIs.

A series of 4-(naphthalen-1-yl)-1,2,5-thiadiazol-3-hydroxyl derivatives (Ia–Im and IIa–IIe) designed as novel HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) was synthesized via an expeditious route and evaluated for their anti-HIV activities in MT-4 cell cultures. All the synthesized compounds were structurally confirmed by spectral analyses. Biological results showed that three analogues displayed moderate inhibitory activity against wild-type (wt) HIV-1 replication with EC₅₀ values ranging from 16 to 22 μm. Molecular docking of compound Ih with wt HIV-1 RT was performed to understand the binding mode between these inhibitors and the wt HIV-1 RT and to rationalize some SARs.

On the basis of structural features, binding mode, and structure–activity relationship studies of two pyrimidine-derived non-nucleoside reverse-transcriptase inhibitors, DABOs, and diaryl pyrimidines, a novel class of 1,2,6-thiadiazine-1,1-dione derivatives were rationally designed using the strategies of bioisosterism and molecular hybridization, synthesized, and evaluated for their anti-HIV activity in MT4 cell cultures. Three compounds were found to have moderate activity against HIV-1 replication with EC₅₀ values ranging from 23 to 32 μm. To further confirm the binding target, compound IIg was selected to conduct an HIV-1 reverse-transcriptase inhibitory assay. In addition, preliminary structure–activity relationship analysis among the newly synthesized compounds was discussed, and the binding mode of the active compound IIg was rationalized by molecular docking and physicochemical studies.

We reported a facile and efficient methodology to synthesize derivatives of pyrrolo[1,2-b][1,2,4,6]thiatriazine (PTTD): a new bridgehead nitrogen heterocyclic system. Treatment of methyl pyrrole-2-carboxylate with N-benzylsulfamoyl chlorides followed by subsequent hydrolysis reaction afforded 1-benzylsulfamoyl-1H-pyrrole-2-carboxylic acids, which underwent ring-closing reaction by treatment with diphenyl phosphorazidate via Curtius rearrangement; subsequent alkylation reaction afforded the desired 2,4-disubstituted-1,1,3-trioxo-2H,4H-PTTDs.

In our continued efforts to discover more active and less toxic HIV-1 non-nucleoside reverse transcriptase inhibitors, we recently designed a novel series of piperidine-linked pyridine analogues on the basis of diarylpyrimidine derivatives, among which two drugs—etravirine and rilpivirine—are approved for use by the US FDA. The title compounds were evaluated for activity against wild-type and resistant mutant strains of HIV-1 as well as HIV-2 in MT-4 cells. The highly potent compound BD-c1 (EC₅₀=10 nM, CC₅₀≥146 μM, SI≥14 126) displays lower cytotoxicity and higher selectivity than etravirine (EC₅₀=2.2 nM, CC₅₀=28 μM, SI=12 884) against wild-type HIV-1. Compound BD-e2 (EC₅₀=5.1 nM) shows greater antiviral efficacy against wild-type HIV-1 than do the four reference drugs nevirapine, delavirdine, efavirenz, and zidovudine. Many compounds were also found to be active against the frequently observed drug-resistant double mutant (K103N+Y181C) HIV-1 strain. Herein we report the design, synthesis, anti-HIV evaluation, preliminary structure–activity relationships, and molecular simulations of novel piperidine-linked pyridine analogues.

The diversity-oriented chemistry synthesis together with the random screening approach has permitted the discovery and optimization of novel antiviral lead compounds. In this paper, a series of novel 5-substituted-2-(4-substituted phenyl)-1,3-benzoxazoles was synthesized and evaluated for their in vitro anti-influenza A virus and anti-influenza B virus activity. The activity was monitored by the MTS assay in the Madin–Darby canine kidney cells. Compound 7h showed excellent inhibitory activity and selective index against A/H3N2 (EC₅₀ = 37.03 μm, SI > 5), which were all higher than that of the reference drug oseltamivir (EC₅₀ > 59.00 μm, SI > 1). However, no compound displays inhibitory activity against influenza B virus.

A series of novel stilbene derivatives containing ligustrazinyl moiety was designed, synthesized, and assayed for their protective effects on damaged endothelial cells. The results showed that most ligustrazinyl stilbene derivatives exhibited high protective effects on the human umbilical vascular endothelial cells (HUVECs) damaged by hydrogen peroxide in comparison with Ligustrazine. The stilbene derivatives A6, A9, A11, A21, A24, A25, and A27 exhibited high potency with low EC₅₀ values ranged from 0.0249 μm to 0.0898 mm. Compound A27 displayed EC₅₀ 0.0249 μm, which is 30 000 times higher than that of Ligustrazine, presenting a most promising lead for further investigation. Structure–activity relationships were briefly discussed.

A series of novel dihydro-alkyloxy-benzyl-oxopyrimidine derivatives were synthesized and evaluated for their activity against influenza virus in Madin–Darby canine kidney cells. Four dihydro-alkyloxy-benzyl-oxopyrimidine derivatives (4a1, 4a2, 4a3, and 4d1) showed potent activity against influenza virus. Among them, compound 4a3 was the most promising lead with broad activity against influenza A (antiviral EC₅₀ values of 9 and 18 μm for the A/H1N1 and A/H3N2 subtype, respectively) and influenza B viruses (EC₅₀: 33 μm). The antiviral mechanism of action of these dihydro-alkyloxy-benzyl-oxopyrimidine derivatives must be quite different from that of the currently approved anti-influenza virus drugs that target the viral M2 or neuraminidase proteins. The dihydro-alkyloxy-benzyl-oxopyrimidine derivatives represent a new avenue for further optimization and development of novel anti-influenza virus agents.

A series of new 5-alkyl-2-phenylaminocarbonylmethylthiopyrimidin-4(3H)-ones bearing variously substituted arylmethyl moieties at the C6 position of the pyrimidine ring were synthesized and evaluated for anti-HIV activity in MT-4 cells. Most of these new congeners exhibited moderate to good activities against the wild-type virus, with EC₅₀ values in the range of 1.40–0.19 μM. Among them, 2-[(4-cyanophenylamino)carbonylmethylthio]-6-(2-chloro-6-fluorobenzyl)-5-ethylpyrimidin-4(3H)-one 4 b6 is one of the compounds endowed with the highest broad-spectrum HIV-1 inhibitory activity, with EC₅₀ values of 0.19±0.005 μM against the wild-type virus, 1.05±0.24 μM (twofold resistance) against the E138K strain, and 2.38±0.13 μM (4.5-fold resistance) against the Y181C strain. Furthermore, reverse transcriptase (RT) inhibition assays against wild-type HIV-1 RT were performed with selected derivatives, confirming that the main target of these compounds is HIV-1 RT and that these new S-DABO analogues act as non-nucleoside RT inhibitors (NNRTIs). Structure–activity relationship and molecular modeling analyses of these new congeners are also discussed.

As part of our studies to discover new HIV-1 reverse transcriptase inhibitors, a series of 3,4-dichlorophenyl substituted 1,2,3-thiadiazole thioacetanilide (TTA=[(1,2,3-thiadiazole-5-yl)sulfanyl]acetanilide) derivatives were synthesized, and in vitro anti-HIV activity was evaluated. The results revealed that nearly half of the compounds show moderate-to-good inhibitory potency against HIV-1. In particular, compound 7f is highly potent, with an EC₅₀ value of 0.95±0.33 μM. The preliminary structure–activity relationship among the newly synthesized congeners is discussed.

A poly(ethylene glycol) (PEG) conjugate of 3′-azido-3′- deoxythymidine (AZT, zidovudine) was designed and synthesized as a novel sustained-release prodrug. In the synthetic process, a succinate diester spacer was used to covalently couple AZT with methoxy poly(ethylene glycol) (mPEG; MW=2000). The conjugate was characterized by Fourier transform infrared (FTIR) and NMR spectroscopies and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS). The in vitro release was determined in hydrochloride (HCl) solution (pH 1.2) and phosphate-buffered solution (PBS; pH 6.8), which showed the release rate of AZT from the conjugate was slower than that from the free drug, suggesting its possible increased retention in gastrointestinal conditions. Pharmacokinetic properties were evaluated experimentally by oral administration in mice. Compared to free AZT, the absorption half-life (t_ka) and elimination half life (t_β) of AZT released from the conjugate were both extended to 0.51±0.03 h (p <0.01) and 2.94±0.24 h (p <0.01), respectively. Evaluation of the in vitro anti-HIV activities showed mPEG-AZT exhibited good inhibition of HIV-1, with an EC₅₀ value of 0.0634 μM, but it is lower than that of free AZT. These results show that the conjugate is capable of releasing the parent drug in a sustained profile, potentially providing a feasible alternative to oral administration of AZT in a clinical setting.

A series of novel 2,4-disubstituted 7-methyl-1,1,3-trioxo-2,4-dihydro-pyrazolo[4,5-e] [1,2,4]thiadiazines (PTDs) was synthesized, structurally confirmed by spectral analysis, and evaluated for their anti-HIV activities by inhibition of HIV-induced cytopathogenicity in MT-4 cell culture. The results showed that some compounds exhibited inhibitory activity specifically against HIV-2 replication. The most active HIV-2 inhibitor was compound 7i (R₁ = benzyl, R₂ = 4-t-butyl-benzyl) with an EC₅₀ value of 18.7 μM and SI=15, which may provide a useful lead for further molecular optimization.