Synthesis and structure–activity relationships of N-(4-amino-2,6-diisopropylphenyl)-N’-(1,4-diarylpiperidine-4-yl)methylureas as anti-hyperlipidemic agents

Based on 1,4-diarylpiperidine-4-methylureas, a new class of ACAT inhibitors, we examined in the study the SAR of a series of compounds prepared by replacing the substituent at the three aromatic parts. Introduction of long alkoxy group onto the phenyl moiety at the B-part was effective in improving both the inhibitory activity for ACAT and the up-regulatory activity for LDL-R expression. Particularly, 3-hydroxypropoxy group (43) on the phenyl moiety of B-part led to improved solubility, while keeping both biological activities. Compound 43 inhibited ACAT activity with an IC₅₀ value of 18 nM, which is superior to that of a known ACAT inhibitor, CI-1011. In addition, compound 43 revealed an LDL-R up-regulatory activity comparable to that of SMP-797. We therefore expect this compound to be a novel ACAT inhibitor.     

A small molecule inhibitor of PCSK9 that antagonizes LDL receptor binding via interaction with a cryptic PCSK9 binding groove

Proprotein convertase (PC) subtilisin kexin type 9 (PCSK9) inhibits the clearance of low density lipoprotein (LDL) cholesterol from plasma by directly interacting with the LDL receptor (LDLR). As the interaction promotes elevated plasma LDL cholesterol levels and a predisposition to cardiovascular disease (CVD), it has attracted much interest as a therapeutic target. While anti-PCSK9 monoclonal antibodies have been successful in the treatment of hypercholesteremia by decreasing CVD risk, their high cost and a requirement for injection have prohibited widespread use. The advent of an orally bioavailable small molecule inhibitor of the PCSK9-LDLR interaction is an attractive alternative, however efforts have been tempered as the binding interface is unfavourable for binding by small organic molecules. Despite its challenging nature, we report herein the discovery of compound 3f as a small molecule inhibitor of PCSK9. The kinase inhibitor nilotinib emerged from a computational screen that was applied to identify compounds that may bind to a cryptic groove within PCSK9 and proximal to the LDLR-binding interface. A subsequent in vitro PCSK9-LDLR binding assay established that nilotinib was a bona fide but modest inhibitor of the interaction (IC₅₀ = 9.8 µM). Through multiple rounds of medicinal chemistry, 3f emerged as a lead-like molecule by demonstrating disruption of the PCSK9-LDLR interaction at nanomolar levels in vitro (IC₅₀ = 537 nM) with no inhibitory activity (IC₅₀ > 10 µM) against a small panel of kinases. Compound 3f restored LDL uptake by liver cells at sub-micromolar levels and demonstrated excellent bioavailability when delivered subcutaneously in mice. Most significantly, compound 3f lowered total cholesterol levels in the plasma of wild-type mice, thereby providing proof-of-concept that the notion of a small molecule inhibitor against PCSK9 is therapeutically viable.     

Ethyl nitrobenzoate: A novel scaffold for cholinesterase inhibition

A series of novel cholinesterase inhibitors containing nitrobenzoate core structure were synthesized by a facile and efficient method. The structure of the novel compounds were fully characterized and confirmed by analytical as well as spectroscopic methods. Compound indicated as 2f was found to possess the best cholinesterase inhibitory activities of all the evaluated compounds. Results suggest that 2f is a selective acetylcholinesterase inhibitor, although it also inhibits butyrylcholinesterase at higher concentration. Kinetics inhibition result suggest that 2f is a mixed-mode inhibitor of acetylcholinesterase. In addition, it was found to have low cytotoxicity. Molecular docking on compound 2f was carried out to rationalize the observed in vitro enzymatic assay results. Most importantly, the potential of nitrobenzoate derivatives as cholinesterase inhibitor was shown through this study. In summary, we discovered nitrobenzoates as a new scaffold that may eventually yield useful compounds in treatment of Alzheimer’s disease.     

Design,synthesis and biological evaluation of novel 6-phenyl-1,3a,4,10b-tetrahydro-2H-benzo[c]thiazolo[4,5-e]azepin-2-one derivatives as potential BRD4 inhibitors

Bromodomain-containing protein 4 (BRD4) is a key epigenetic regulator in cancer, and inhibitors targeting BRD4 exhibit great anticancer activity. By replacing the methyltriazole ring of the BRD4 inhibitor I-BET-762 with an N-methylthiazolidone heterocyclic ring, fifteen novel BRD4 inhibitors were designed and synthesized. Compound 13f had a hydrophobic acetylcyclopentanyl side chain, showing the most potent BRD4 inhibitory activity in the BRD4-BD1 inhibition assay (IC₅₀ value of 110 nM), it also significantly suppressed the proliferation of MV-4-11 cells with high BRD4 level (IC₅₀ value of 0.42 μM). Furthermore, the potent apoptosis-promoting and G0/G1 cycle-arresting activity of compound 13f were indicated by flow cytometry. As the downstream-protein of BRD4, c-Myc was in significantly low expression by compound 13f treatment in a dose-dependent manner. All the findings supported that this novel compound 13f provided a perspective for developing effective BRD4 inhibitors.     

Discovery of thiapyran-pyrimidine derivatives as potential EGFR inhibitors

A series of novel thiapyran-pyrimidine derivatives (10a–10h, 11a–11g, 12a–12f, 13a–13f, 14a–14f) were synthesized and their antiproliferative activities were tested. Most of the target compounds showed good activity on one or more cancer cell lines but low activity on human normal cell LO2. The most promising compound 13a exhibited the similar IC₅₀ values on A549 and H1975 cell lines to the lead drug Olmutinib, and exhibited excellent activity and selectivity on EGFR^T790M/L858R in the kinase experiment. AO and Hoechst33258 staining indicated that 13a could effectively induce H1975 cells apoptosis. Cell cycle and apoptosis analysis suggested that 13a could block cancer cells in G2/M phase and induce into late apoptosis in a manner of concentration-dependent. The structure–activity relationship of 13a was analyzed to explore its mechanism. All the results showed that 13a was a promising EGFR inhibitor.     

Design,synthesis, and biological evaluation of histone deacetylase inhibitors possessing glutathione peroxidase-like and antioxidant activities against Alzheimer’s disease

A series of hybrids containing the pharmacophores of the histone deacetylase (HDAC) inhibitor, SAHA, and the antioxidant ebselen were designed and synthesized as multi-target-directed ligands against Alzheimer’s disease. An in vitro assay indicated that some of these molecules exhibit potent HDAC inhibitory activity and ebselen-related pharmacological effects. Specifically, the optimal compound 7f was found to be a potent HDAC inhibitor (IC₅₀?=?0.037?μM), possessing rapid hydrogen peroxide scavenging activity and glutathione peroxidase-like activity (ν₀?=?150.0?μM?min^?1) and good free oxygen radical absorbance capacity (value of ORAC: 2.2). Furthermore, compound 7f showed significant protective effects against damage induced by H₂O₂ and the ability to prevent ROS accumulation in PC12 cells.     

Design,synthesis and biological evaluation of novel indole-xanthendione hybrids as selective estrogen receptor modulators

Ground breaking clinical therapeutic advances in the treatment of breast cancer (BC) is the introduction of selective estrogen receptor modulators (SERMs). We have expeditiously designed and synthesized indole-xanthendione hybrids by coalescing the indole nucleus with xanthendione. All the compounds were first screened for anti-proliferative activity, cytotoxicity and ER-α binding affinity by utilizing ER-α dominant T47D BC cell lines, PBMCs and ER-α competitor assay kit. From this study, two representative compounds 6e and 6f showing most promising activity were advanced for gene expression studies for targeting ER-α. Cell imaging experiment undoubtedly indicate that both the compounds were able to cross cellular bio membrane and accumulate thus instigating cytotoxicity. RT-PCR and Western blotting experiments further strengthened that both compounds altered the expression of mRNA and receptor protein of ER-α, thereby forestalling downstream transactivation and signalling pathway in T47D cells line. Structural investigation from induced fit simulation study suggest that indole moiety of the compounds 6e and 6f helps in the anchoring of the xanthendione moiety in the hydrophobic region of the cavity thus enabling the compound to bind in antagonistic conformation similar to bazedoxifene by extensive hydrogen bonding and Van der Waals forces. All these finding collectively imply that compound 6e and 6f represents a novel potent ER-α antagonist and in the development of SERMs for the management of BC.     

Synthesis of thymol-based pyrazolines: An effort to perceive novel potent-antimalarials

A series of thymol based substituted pyrazolines and chalcones was synthesized and evaluated for antimalarial activity, using in-vitro and in-vivo malaria models. All the target compounds (5a-k and 6a-j) were found to be active against human malaria parasite strain Plasmodium falciparum NF54. Among all, compounds 5e and 5f of chalcone series and 6c and 6f of pyrazoline series exhibited prominent antimalarial activity with IC₅₀ less than 3 and 2 μM respectively, while other pyrazolines also significantly inhibited the P. falciparum with IC₅₀ less than 10 μM. The designed pharmacophores were found to be effective against P. falciparum. Compound 6f was found to be able to retard malaria progression in mice. This was evident through decreased parasitemia, increased mean survival time and hemoglobin content in the treated animals. Moreover, 6f was observed as an inhibitor of heme polymerization pathway of the malaria parasite. It also inhibited free heme degradation, which could be possibly responsible for higher reactive oxygen species (ROS) in parasite, thus inhibiting the rapid proliferation of the parasite. In addition to this, compound 6f was found to be non-toxic with a good selectivity index. Based on these observations, the compound 6f could be taken up for further antimalarial lead optimization studies.     

Synthesis,evaluation and docking of novel pyrazolo pyrimidines as potent p38α MAP kinase inhibitors with improved anti-inflammatory,ulcerogenic and TNF-α inhibitory properties

A series of nine new N-substituted-4-((1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl)amino)benzamides (6a-i) derivatives was synthesized. All the compounds were screened in-vitro for BSA anti-denaturation property, antioxidant assay and p38α MAP kinase inhibition. The in vitro anti-inflammatory assay results revealed that the compounds (6f-i) showed better activity than the compounds 6a-e. Compound 6f bearing the 4-chlorophenyl group showed in vitro anti-inflammatory activity (82.35 ± 4.04) comparable to standard drug diclofenac sodium (84.13 ± 1.63) and better p38α MAP kinase inhibitory activity (IC₅₀ = 0.032 ± 1.63 µM) than the prototypic inhibitor SB203580 (IC₅₀ = 0.041 ± 1.75 µM). The selected active compounds (6f-i) were further studied in animal models for anti-inflammatory activity, ulcerogenic liability, lipid peroxidation and TNF-α inhibition potential. Compound 6f showed promising anti-inflammatory potential with a percentage inhibition of 83.73% when compared to the standard, diclofenac sodium (78.05%). Compound 6f was also found to show reduced ulcerogenic liability and lipid peroxidation in comparison to the standard. This compound also potently inhibited the lipopolysaccharide (LPS)-induced TNF-α production in mice model (ID₅₀ = 8.23 mg/kg) in comparison to SB 203580 (ID₅₀ = 26.38 mg/kg). The molecular docking of compounds 6a-i against p38α MAP kinase receptor was also performed to understand ligand receptor interaction. Amongst all synthesized molecules compound 6f displayed highest docking score of −9.824. It showed hydrogen bonding interactions with Asn115 and pi-cation interaction with Lys53.     

New benzyl pyridinium derivatives bearing 2,4-dioxochroman moiety as potent agents for treatment of Alzheimer’s disease: Design,synthesis, biological evaluation,and docking study

A new series of benzyl pyridinium-2,4-dioxochroman derivatives 7a-o was synthesized and evaluated as new anti-Alzheimer agents. Among the synthesized compounds, the compounds 7f and 7i exhibited the most potent anti-AChE and anti-BuChE activities, respectively. The kinetic study of the compound 7f revealed that this compound inhibited AChE in a mixed-type inhibition mode. Furthermore, the docking study of the compounds 7f and 7i showed that these compounds bound to both the catalytic site (CS) and peripheral anionic site (PAS) of AChE and BuChE, respectively. The compound 7f also exhibited a greater self-induced Aβ peptide aggregation inhibitory activity in compare to donepezil. Furthermore, the neuroprotective activity of this compound at 20 μM was comparable to that of the standard neuroprotective agent (quercetin).     

Expanding the structural diversity of diarylureas as multi-target tyrosine kinase inhibitors

Recently approved multi-target inhibitors of receptor tyrosine kinases (RTKs) have significantly improved the clinical treatment of cancers. A series of N,N′-diarylureas incorporated with aromatic heterocycle have been designed, synthesized and evaluated as novel multi-target RTK inhibitors. The preliminary biological evaluation indicated that several compounds exhibited comparable potency with Sorafenib. Among them, compound 6f was identified as the most potent multikinase inhibitor of EGFR, KDR and FGFR1 with IC₅₀ values of 14.83 nM, 21.57 nM, and 28.23 nM, respectively. These compounds expanded the structural diversity of diarylureas as RTK inhibitors. The results demonstrated that compound 6f could be served as novel lead compound for further development of multi-target RTK inhibitors.     

Design,synthesis and evaluation of N-hydroxypropenamides based on adamantane to overcome resistance in NSCLC

A series of novel N-hydroxypropenamides containing adamantane moiety were identified and most of them exhibited HDAC inhibitory activity and could reverse the resistance of cisplatin in NSCLC cell lines. In this process, molecular docking was employed to verify the rationality of designing, subsequently, target compounds were synthesized and conducted to enzyme- and cell-based biological evaluation. Most of synthesized compounds could inhibit HDAC activity with the IC₅₀ values lower than 50 nM and result in the increase of Ac-H4 and p21 in A549 cells. Importantly, we assessed the reversal effect of those compounds and found several compounds display an anti-resistant effect in lung cancer cells, especially compound 8f.As compared to belinostat and cisplatin, compound 8f showed improved inhibitory activity against A549/CDDP cell lines with IC₅₀ value of 5.76 μM, and far lower resistance index of 1.24. Moreover, the structure–activity relationships of these compounds were summarized and compound 8f could serve as a research tool for identifying the mechanism of reversing resistance and a template for designing novel compounds to reverse cisplatin resistance.     

Synthesis and evaluation of 4-(2-hydroxypropyl)piperazin-1-yl) derivatives as Hsp90 inhibitors

We previously reported 4-(3-((6-bromonaphthalen-2-yl)oxy)-2-hydroxypropyl)-N,N-dimethylpiperazine-1-sulfonamide (1) as a novel heat shock protein 90 inhibitor with moderate activity. In our ongoing efforts for the discovery of Hsp90 modulators we undertake structural investigations on 1. Series of the titled compound were designed, synthesized and evaluated. We have found that compounds with a hydroxyl group at C-4 of the aryl ring on the piperazine moiety possess Hsp90 inhibition properties. Compound 6f with improved activity could be further developed and optimized as Hsp90 inhibitor.     

Click chemistry-assisted synthesis of novel aminonaphthoquinone-1,2,3-triazole hybrids and investigation of their cytotoxicity and cancer cell cycle alterations

A series of 12 novel 1,4-naphthoquinone-1,2,3-triazole hybrids were designed and synthesized through copper-catalyzed click reaction of 2-(prop-2-ynylamino)naphthalene-1,4-dione (3) and different azidomethyl-benzene derivatives. The synthesized compounds were assessed for their anticancer activity against three cancer cell lines (MCF-7, HT-29 and MOLT-4) by MTT assay. The results showed that the majority of the synthesized compounds displayed cytotoxic activity. Derivatives 6f and 6h, bearing 4-trifluoromethyl-benzyl and 4-tert-butyl-benzyl groups, respectively, as well as intermediate 3 demonstrated good cytotoxic potential against all tested cancer cell lines, among which compound 6f showed the highest activity. Flow cytometric analysis revealed that compounds 3, 6f and 6h arrested cell cycle at G0/G1 phase in MCF-7 cells. Therefore, synthesized aminonaphthoquinone-1,2,3-triazole derivatives can be introduced as promising molecules for further development as potential anticancer agents.     

Novel cytisine derivatives exert anti-liver fibrosis effect via PI3K/Akt/Smad pathway

A series of new cytisine derivatives with a unique endocyclic scaffold were synthesized and evaluated for their inhibitory effect on collagen α1 (I) (COL1A1) promotor in human LX2 cells, taking cytisine as the lead. Structure-activity relationship (SAR) revealed that introducing a 12N-benzyl substitution might significantly enhance the activity. Compound 5f exhibited a promising inhibitory potency against COL1A1 with an IC₅₀ value of 12.8 μM in human LX2 cells, and an inspiring inhibition activity against COL1A1 on both mRNA and protein levels. It also effectively inhibited the expression of α smooth muscle actin (α-SMA), connective tissue growth factor (CTGA), matrix metalloprotein 2 (MMP-2), and transforming growth factor β1 (TGFβ1), indicating an extensive inhibitory effect against fibrogenetic proteins. In addition, compound 5f displayed reasonable PK and safety profiles. The primary mechanism study indicated that it might repress the hepatic fibrogenesis via PI3K/Akt/Smad signaling pathway. The results provided powerful information for further structure optimization, and compound 5f was selected as a novel anti-liver fibrosis agent for further investigation.     

Design,synthesis and evaluation of new 4-arylthiazole-2-amine derivatives as acetylcholinesterase inhibitors

A series of new 4-arylthiazole-2-amine derivatives as acetylcholinesterase inhibitors (AChEIs) were designed and synthesized, Furthermore, their inhibitory activities against acetylcholinesterase in vitro were tested by Ellman spectrophotometry, and the results of inhibitory activity test showed that most of them had a certain acetylcholinesterase inhibitory activity in vitro. Moreover, the IC₅₀ value of compound 4f was to 0.66 μM, which was higher than that of Rivastigmine and Huperzine-A as reference compounds, and it had a weak inhibitory effect on butyrylcholinesterase. The potential binding mode of compound 4f with AChE was investigated by the molecular docking, and the results showed that 4f was strongly bound up with AChE with the optimal conformation, in addition, their binding energy reached −11.27 Kcal*mol⁻¹. At last, in silico molecular property of the synthesized compounds were predicted by using Molinspiration online servers. It can be concluded that the lead AChEIs compound 4f presented satisfactory drug-like characteristics.     

Discovery of 3-benzyl-1,3-benzoxazine-2,4-dione analogues as allosteric mitogen-activated kinase kinase (MEK) inhibitors and anti-enterovirus 71 (EV71) agents

Enterovirus 71 (EV71) is a kind of RNA virus and one of the two causes of Hand, foot and mouth disease (HFMD). Inhibitors that target key components of Ras/Raf/MEK/ERK pathway in host cells could impair replication of EV71. A series of 3-benzyl-1,3-benzoxazine-2,4-diones were designed from a specific MEK inhibitor G8935, by replacing the double bond between C3 and C4 within the coumarin scaffold with amide bond. One compound (9f) showed submicromolar inhibitory activity among the 12 derivatives. Further optimization on 9f led to two active compounds (9k and 9m) with nanomolar bioactivities (55 nM and 60 nM). The results of enzymatic assays also demonstrated that this series of compounds were allosteric inhibitors of unphosphorylated MEK1. The binding mode of compound 9k was predicted by molecular dynamic simulation and the key interactions were same as published MEK1/2 allosteric inhibitors. In the cell-based assays, compounds 9k and 9m could effectively suppress the ERK1/2 pathway, expression of EV71 VP1, and EV71 induced cytopathic effect (CPE) in rhabdomyosarcoma (RD) cells.     

Synthesis,molecular properties prediction and biological evaluation of indole-vinyl sulfone derivatives as novel tubulin polymerization inhibitors targeting the colchicine binding site

Twenty-two novel indole-vinyl sulfone derivatives were designed, synthesized and evaluated as tubulin polymerization inhibitors. The physicochemical and drug-likeness properties of all target compounds were predicted by Osiris calculations. All compounds were evaluated for their antiproliferative activities, among them, compound 7f exhibited the most potent activity against a panel of cancer cell lines, which was 2–7 folds more potent than our previously reported compound 4. Especially, 7f displayed about 8-fold improvement of selective index as compared with compound 4, indicating that 7f might have lower toxicity. Besides, 7f inhibited the microtubule polymerization by binding to the colchicine site of tubulin. Further investigations showed that compound 7f effectively disrupted microtubule network, caused cell cycle arrest at G2/M phase and induced cell apoptosis in K562 cells. Moreover, 7f reduced the cell migration and disrupted capillary-like tube formation in HUVEC cells. Importantly, the in vivo anti-tumor activity of 7f was validated in H22 liver cancer xenograft mouse model without apparent toxicity, suggesting that 7f is a promising anti-tubulin agent for cancer therapy.     

Design,synthesis and biological evaluation of novel series of 2H-benzo[b][1,4]oxazin-3(4H)-one and 2H-benzo[b][1,4]oxazine scaffold derivatives as PI3Kα inhibitors

The abnormal activation of PI3K signaling pathway leads to the occurrence of various cancers. The PI3Kα is frequently mutated and overexpressed in many human cancers. Therefore, the PI3Kα was considered as a promising target in therapeutic treatment of cancer. In this study, two series of compounds containing 2H-benzo[b][1,4]oxazin-3(4H)-one and 2H-benzo[b][1,4]oxazine scaffold were synthesized and evaluated antiproliferative activities against three cancer cell lines, including HCT-116, MDA-MB-231 and SNU638. Compound 7f with the most potent antiproliferative activity was selected for further evaluation on normal cells and PI3K kinase. Studies indicated that compound 7f could decrease the phospho-Akt (T308) in a dose-dependent manner. Four key hydrogen bonding interactions were found in the docking of 7f with PI3K enzyme. All the results suggested that 7f was a potent PI3Kα inhibitor.