Wenmin Chen

8-Hydroxyquinoline: a privileged structure with a broad-ranging pharmacological potential

Privileged structures can bind to a diverse range of targets with high affinities, thus benefiting the discovery of novel bioactive agents. 8-Hydroxyquinoline derivatives represent an important type of “privileged structure”, possessing a rich diversity of biological properties. Numerous encouraging investigations have demonstrated that this privileged structure should be further exploited for therapeutic applications in the future. In view of its predominance, and on the basis of our research interest in this scaffold, an updated and detailed account of the pharmacological properties of 8-hydroxyquinoline derivatives, as well as recent insights from structural biology, are described. Finally, some outlooks on current issues and future directions in this field of research are also provided.

Fused heterocycles bearing bridgehead nitrogen as potent HIV-1 NNRTIs. Part 4: Design, synthesis and biological evaluation of novel imidazo[1,2-a]pyrazines

Through a structure-guided core-refining approach, a series of novel imidazo[1,2-a]pyrazine derivatives were designed, synthesized and evaluated as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). Biological results of antiviral assay in MT-4 cell cultures showed that 12 target compounds displayed moderate activities against wild-type (wt) HIV-1 strain (IIIB) with EC50 values ranging from 0.26 μM to 19 μM. Among them, 4a and 5a were found to be the two most active analogues possessing EC50 values of 0.26 μM and 0.32 μM respectively, comparable to delavirdine (DLV, EC50 = 0.54 μM) and nevirapine (NVP, EC50 = 0.31 μM) in a cell-based assay. Additionally, 9 compounds showed RT inhibitory activity superior to that of NVP. Moreover, some predicted drug-like properties of representative compounds 4a and 5a, as well as the structure-activity relationship (SAR) analysis were discussed in detail. The binding mode of compound 4a was investigated by molecular simulation studies.

Design, synthesis and anti-HIV evaluation of novel diarylnicotinamide derivatives (DANAs) targeting the entrance channel of the NNRTI binding pocket through structure-guided molecular hybridization

Through a structure-based molecular hybridization approach, a novel series of diarylnicotinamide derivatives (DANAs) targeting the entrance channel of HIV-1 NNRTIs binding pocket (NNIBP) were rationally designed, synthesized and evaluated for their anti-HIV activities in MT-4 cells together with the inhibition against the reverse transcriptase (RT) in an enzymatic assay. Encouragingly, most of the new DANAs were found to be active against wild-type HIV-1 with an EC50 in the range of 0.027-4.54 μM. Among them, compound 6b11 (EC50 = 0.027 μM, SI > 12518) and 6b5 (EC50 = 0.029 μM, SI = 2471) were identified as the most potent inhibitors, which were more potent than the reference drugs nevirapine (EC50 = 0.31 μM) and delavirdine (EC50 = 0.66 μM). Some DANAs were also active at micromolar concentrations against the K103N + Y181C resistant mutant. Compound 6b11 exhibited the highest enzymatic inhibition activity (IC50 = 20 nM), which is equal to that of efavirenz (EC50 = 20 nM) and 31 times higher than that of nevirapine (EC50 = 0.62 μM). Preliminary structure-activity relationships (SARs) and molecular modeling of these new DANAs have been discussed.

Discovery of novel diarylpyrimidines as potent HIV NNRTIs via a structure-guided core-refining approach

Guided by crystal structures of HIV-1 RT/DAPY complex and molecular modeling studies, a series of novel DAPY derivatives were rationally designed, synthesized and evaluated for their anti-HIV activities. Among them, 16 compounds significantly inhibited HIV-1 IIIB replication with EC50 values lower than 66 nM. Particularly, compound 7a was the most potent inhibitor against HIV-1 wild-type and double RT mutant HIV-1 strain K103N/Y181C, with an EC50 value of 2.5 nM (SI = 13,740) and 0.33 μM (SI = 107), respectively. Unexpectedly, compound 8c was found to show moderate anti-HIV-2 potency (EC50 = 5.57 μM). Preliminary structure-activity relationships (SARs) and molecular modeling of these new analogues were also discussed in detail.

Structure-based bioisosterism design, synthesis and biological evaluation of novel 1,2,4-triazin-6-ylthioacetamides as potent HIV-1 NNRTIs

The development of new HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) offers the possibility of generating novel chemical entities of increased potency. Previous investigations in our laboratory resulted in the discovery of several novel series of arylazolylthioacetanilides as potent NNRTIs. In this study, based on the structure-based bioisosterism strategy, novel 1,2,4-triazin-6-yl thioacetamide derivatives were designed, synthesized and evaluated for their anti-HIV activity in MT-4 cells. Among them, the most promising compound was 8b15 with double-digit nanomolar activity against wild-type HIV-1 (EC(50)=0.018±0.007 μM) and moderate activity against the double mutant strain RES056 (EC(50)=3.3±0.1 μM), which indicated that 1,2,4-triazin-6-yl thioacetamide can be used as a novel scaffold to develop a new class of potent NNRTIs active against both wild-type and drug-resistant HIV-1 strains. In addition, preliminary structure-activity relationship (SAR) and molecular modeling results are also briefly discussed, which provide some useful information for the further design of novel NNRTIs.

Discovery of 2-pyridone derivatives as potent HIV-1 NNRTIs using molecular hybridization based on crystallographic overlays

Based on crystallographic overlays of the known inhibitors TMC125 and R221239 complexed in RT, we designed a novel series of 4-phenoxy-6-(phenylamino)pyridin-2(1H)-one derivatives as HIV NNRTIs by molecular hybridization approach. The biological testing results indicated that 2-pyridone scaffold of these inhibitors was indispensable for their anti-HIV-1 activity, and substitution of halogen at the 3-position of the 2-pyridone ring would decrease the anti-HIV activity. Four most potent compounds had anti-HIV-1 IIIB activities at low micromolar concentrations (EC₅₀=0.15-0.84 μM), comparable to that of nevirapine and delavidine. Some compounds were selected to test their anti-HIV-1 RT inhibitory action and to perform molecular modeling studies to predict the binding mode of these 2-pyridone derivatives.

Synthesis and Anti-HIV Activity of 4-(Naphthalen-1-yl)-1,2,5-thiadiazol-3-hydroxyl Derivatives

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.

Discovery of novel 2-(3-(2-chlorophenyl)pyrazin-2-ylthio)-N-arylacetamides as potent HIV-1 inhibitors using a structure-based bioisosterism approach.

The present work is an extension of our ongoing efforts towards the development and identification of new molecules with anti-HIV activity which have previously led to the discovery of arylazolylthioacetanilides as highly active NNRTIs. In this article, a series of 2-2-(3-(2-chlorophenyl)pyrazin-2-ylthio)-N-arylacetamide derivatives were synthesized and evaluated for in vitro anti-HIV activity. Most of the tested compounds exhibited moderate activities against wild-type HIV-1. Among them, compound 6k showed significant activity against wild-type HIV-1 with an EC(50) value of 1.7μM, along with moderate activity against wild-type reverse transcriptase (RT). The preliminary structure-activity relationship (SAR) and docking calculations of this new series of compounds were also investigated, which may help designing more potent molecules.

Ligustrazine Derivatives. Part 8: Design, Synthesis, and Preliminary Biological Evaluation of Novel Ligustrazinyl Amides as Cardiovascular Agents

A series of novel Ligustrazinyl amides was designed, synthesized and evaluated for their protective effect on the injured vascular endothelial cells. The preliminary results demonstrated that some compounds possessed more potent activities than that of Ligustrazine in stimulating replication of the injured human umbilical vascular endothelial cells (HUVECs) that is damaged by hydrogen peroxide. Among the active compounds, compounds 8i, 8t and 8u exhibited the highest potency with low EC₅₀ values of 0.037, 0.070 and 0.055 mM, respectively. Structure-activity relationships were briefly discussed.

Discovery of novel pyridazinylthioacetamides as potent HIV-1 NNRTIs using a structure-based bioisosterism approach

In continuation of our endeavors to develop new, potent, selective, and less toxic anti-HIV agents, we describe our structure-based bioisosterism design, synthetic strategy, and structure–activity relationship (SAR) studies that led to the identification of pyridazinylthioacetamides, a novel class of NNRTIs, isosteres of arylazolylthioacetanilide derivatives. Nearly all of the tested compounds inhibited HIV-1 strain IIIB replication in the lower micromolar concentration range (EC50: 0.046–5.46 μM). Notably, the most promising compound 8k exhibited extremely potent inhibitory activity against HIV-1 replication with an EC50 value of 0.046 μM, CC50 of 99.9 μM and the viral selectivity index amounted to 2149. These values were much better than those of NVP (EC50 = 0.09 μM) and DDC (EC50 = 1.04 μM). Compound 8k also exhibited moderate inhibition of enzymatic activity with an IC50 value of 4.06 μM, which was of the same order of magnitude as that of NVP (2.74 μM). Docking calculations were also performed to investigate the binding mode of compound 8k into the non-nucleoside binding site of HIV-1 RT and to rationalize some SARs.