Design,synthesis and evaluation of 2-amino-imidazol-4-one derivatives as potent β-site amyloid precursor protein cleaving enzyme 1 (BACE-1) inhibitors

Inhibition of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) to prevent brain β-amyloid (Aβ) peptide’s formation is a potential effective approach to treat Alzheimer’s disease. In this report we described a structure-based optimization of a series of BACE1 inhibitors derived from an iminopyrimidinone scaffold W-41 (IC₅₀ = 7.1 μM) by Wyeth, which had good selectivity and brain permeability but low activity. The results showed that occupying the S₃ cavity of BACE1 enzyme could be an effective strategy to increase the biological activity, and five compounds exhibited stronger inhibitory activity and higher liposolubility than W-41, with L-5 was the most potent inhibitor against BACE1 (IC₅₀ = 0.12 μM, logP = 2.49).     

Potent ACE inhibitors from 5-hydroxy indanone derivatives

A novel triazole derivatives(±)-2-(hydroxymethyl)-7,8-dihydro-1H-indeno[5,4-b]furan-6(2H)-one (12a–j) were designed and synthesized by the reaction between racemic azide and terminal acetylenes under click chemistry reaction conditions followed by biological evaluation as angiotensin converting enzyme (ACE) inhibitors. β-Amino alcohol derivatives of 1-indanone (15a–l) were synthesized from 5-hydroxy indanone, it was reacted with epichlorohydrin and followed by oxirane ring opening with various piperazine derivatives. Among the newly synthesized compounds 12b (IC₅₀: 1.388024 µM), 12g (IC₅₀: 1.220696 µM), 12j (IC₅₀: 1.312428 µM) and 15k (IC₅₀: 1.349671 µM) and 15l (IC₅₀: 1.330764 µM) emerged as most active non-carboxylic acid ACE inhibitors with minimal toxicity comparable to clinical drug Lisinopril.     

Synthesis and biological evaluation of quinazolinone-based hydrazones with potential use in Alzheimer’s disease

Discovering multifunctional agents for the treatment of Alzheimer’s disease (AD) is an attractive therapeutic approach. BACE1 (β-site amyloid precursor protein cleaving enzyme 1) inhibitors may play a pivotal role in treating AD. Therefore, the discovery of novel non-peptide BACE1 inhibitors with desirable blood brain barrier permeability is a favorable approach for treatment. Moreover, the antioxidant potential of a drug could serve as an added value for designing dual-acting therapeutic agents. Here, we report the design, synthesis and biological evaluation of quinazolinone-hydrazone derivatives as new multi-target candidates for the treatment of AD. The compounds were investigated for their in vitro BACE1 inhibitory potential using a FRET-based enzymatic assay and also screened for antioxidant activity using DPPH. Among them, compound 4h bearing a 2,3-dichlorophenyl moiety showed the highest activity with an IC₅₀ value of 3.7 μM against BACE1. In addition, compound 4i with a 2,4-dihydroxyphenyl scaffold demonstrated moderate BACE1 inhibitory activity (IC₅₀ = 27.6 μM) with a significant antioxidant effect (IC₅₀ = 8.4 μM). Furthermore, docking studies revealed strong interaction between compound 4h and the key residues of BACE1 active site. These results demonstrate that quinazolinone-hydrazone derivatives represent a valuable scaffold for the discovery of novel non-peptidic BACE1 inhibitors.     

Diastereoselective synthesis of fused cyclopropyl-3-amino-2,4-oxazine β-amyloid cleaving enzyme (BACE) inhibitors and their biological evaluation

The diastereoselective synthesis and structure activity relationship (SAR) of a series of fused cyclopropyl-3-amino-2,4-oxazine (2-oxa-4-azabicyclo[4.1.0]hept-3-en-3-amine)-containing BACE inhibitors is described. Through these efforts compound 2 was identified as a potent (cell IC₅₀ = 15?nM) BACE inhibitor with acceptable ADME properties. When tested in vivo, compound 2 demonstrated a significant reduction of brain and cerebral spinal fluid (CSF) Aβ₄₀ levels (46% and 66%, respectively) in a rat pharmacodynamic study and thus represents a suitable starting point for the further development of in vivo efficacious compounds for the treatment of Alzheimer's disease.     

Sulfonamido-derivatives of unsubstituted carbazoles as BACE1 inhibitors

A novel series of variously substituted N-[3-(9H-carbazol-9-yl)-2-hydroxypropyl]-arylsulfonamides has been synthesized and assayed for β-Secretase (BACE1) inhibitory activity. BACE1 is a widely recognized drug target for the prevention and treatment of Alzheimer's Disease (AD). The introduction of benzyl substituents on the nitrogen atom of the arylsulfonamide moiety has so far led to the best results, with three derivatives showing IC₅₀ values ranging from 1.6 to 1.9?μM. Therefore, a significant improvement over the previously reported series of N-carboxamides (displaying IC₅₀’s?≥?2.5?μM) has been achieved, thus suggesting an active role of the sulfonamido-portion in the inhibition process. Preliminary molecular modeling studies have been carried out to rationalize the observed structure-activity relationships.     

Synthesis and bioevaluation of 6-chloropyridazin-3-yl hydrazones and 6-chloro-3-substituted-[1,2,4]triazolo[4,3-b]pyridazines as cytotoxic agents

An efficient synthesis of a series of 6-chloro-3-substituted-[1,2,4]triazolo[4,3-b]pyridazines is described via intramolecular oxidative cyclization of various 6-chloropyridazin-3-yl hydrazones with iodobenzene diacetate. The structures of the newly synthesized compounds were assigned on the basis of elemental analysis, IR, NMR (¹H and ¹³C) and mass spectral data. All the thirty three compounds 3a-q and 4b-q synthesized in the present study were evaluated for their in vitro cytotoxic activities against two Acute Lymphoblastic Leukemia (ALL) cell lines named, SB-ALL and NALM-6, and a human breast adenocarcinoma cell lines (MCF-7). The results revealed that triazoles 4 exhibit better cytotoxicity than their hydrazone precursors 3. Among triazoles, compounds 4f, 4j and 4q exhibited potent cytotoxic activity against SB-ALL and NALM-6 with IC₅₀ values in the range of ∼1.64–5.66 μM and ∼1.14–3.7 μM, respectively, compared with doxorubicin (IC₅₀ = 0.167 μM, SB-ALL). Compounds 4f, 4j and 4q were subjected to apoptosis assay after 48 h treatment and these compounds induced apoptosis of NALM-6 cells via caspase 3/7 activation. Results revealed that compound 4q represents potential promising lead.     

Discovery of new inhibitors against both NF-κB and osteoclastogenesis from in-house library with α, β-unsaturated-enone fragment

The α,β-unsaturated-enone contained natural products have been reported showing NF-κB inhibition effect. It is well known that NF-κB inhibitors can also be used to inhibit osteoclastogenesis. In a continual discovery new agents for anti-osteoclastogenesis, 8 different type compounds with α,β-unsaturated-enone fragments from our in-house library were evaluated for NF-κB inhibition and anti-osteoclastogenesis. Experimental results indicated five compounds exhibited inhibition of NF-κB signal pathway. Among them, one compound ((E)-2-(4-fluorobenzylidene)-3,4-dihydronaphthalen-1(2H)-one, 6a) simultaneously inhibits both osteoclastogenesis and NF-κB signal pathway. Furthermore, 12 compounds with similar scaffold with 6a were tested for anti-osteoclastogenesis. As a result, 9 compounds inhibited both NF-κB and osteoclastogenesis. Among them, compound 6b is the most potent inhibitor against NF-κB (IC₅₀ = 2.09 μM) and osteoclast differentiation (IC₅₀ = 0.86 μM). Further studies show that compound 6b blocks the phosphorylation of both p65 and IκBα, and suppresses NF-κB targeted gene expression without interfering MAPKs and PI3K/Akt signal transduction pathways. This study demonstrates that we can identify promising synthesized compounds with new scaffolds as therapeutic solutions against osteoclastogenesis inspired by the privileged fragment derived from natural leads.     

Design and synthesis of novel anti-Alzheimer’s agents: Acridine-chromenone and quinoline-chromenone hybrids

A novel series of acridine-chromenone and quinoline-chromenone hybrids were designed, synthesized, and evaluated as anti-Alzheimer’s agents. All synthesized compounds were evaluated as cholinesterases (ChEs) inhibitors and among them, 7-(4-(6-chloro-2,3-dihydro-1H-cyclopenta[b]quinolin-9-ylamino)phenoxy)-4-methyl-2H-chromen-2-one (8e) exhibited the most potent anti-acetylcholinesterase (AChE) inhibitory activity (IC₅₀ = 16.17 μM) comparing with rivastigmine (IC₅₀ = 11.07 μM) as the reference drug. Also, compound 8e was assessed for its β-secretase (BACE1) inhibitory and neuroprotective activities which demonstrated satisfactory results. It should be noted that both kinetic study on the inhibition of AChE and molecular modeling revealed that compound 8e interacted simultaneously with both the catalytic active site (CAS) and peripheral anionic site (PAS) of AChE.     

Novel N-benzylpyridinium moiety linked to arylisoxazole derivatives as selective butyrylcholinesterase inhibitors: Synthesis,biological evaluation,and docking study

A novel series of N-benzylpyridinium moiety linked to arylisoxazole ring were designed, synthesized, and evaluated for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Synthesized compounds were classified into two series of 5a-i and 5j-q considering the position of positively charged nitrogen of pyridinium moiety (3- or 4- position, respectively) connected to isoxazole carboxamide group. Among the synthesized compounds, compound 5n from the second series of compounds possessing 2,4-dichloroaryl group connected to isoxazole ring was found to be the most potent AChE inhibitor (IC₅₀ = 5.96 µM) and compound 5j also from the same series of compounds containing phenyl group connected to isoxazole ring demonstrated the most promising inhibitory activity against BChE (IC₅₀ = 0.32 µM). Also, kinetic study demonstrated competitive inhibition mode for both AChE and BChE inhibitory activity. Docking study was also performed for those compounds and desired interactions with those active site amino acid residues were confirmed through hydrogen bonding as well as π-π and π-anion interactions. In addition, the most potent compounds were tested against BACE1 and their neuroprotectivity on Aβ-treated neurotoxicity in PC12 cells which depicted negligible activity. It should be noted that most of the synthesized compounds from both categories 5a-i and 5j-q showed a significant selectivity toward BChE. However, series 5j-q were more active toward AChE than series 5a-i.     

Synthesis and anticancer evaluation of 3-aryl-6-phenylimidazo[2,1-b]thiazoles

A series of new 3,6-diphenylimidazo[2,1-b]thiazole derivatives (4a–l) are synthesized and evaluated for their anticancer activity. Some of the synthesized compounds have shown potent anti-proliferative activity against HeLa, MDA-MB-231, A549 and THP1 human cancer cell lines. Among the active compounds, 3-(3-trifluoromethylphenyl)-6-phenylimidazo[2,1-b]thiazole (4j) has caused significant cytotoxicity in HeLa cells, with IC₅₀ as low as 6.5 μM. Compound 4j has induced caspase-3 and caspase-8 activation, leading to an apoptotic cell death. FACS analysis has revealed that compound 4j arrests cells in G0/G1 phase. The presence of 3-(3-trifluoromethylphenyl)- or 3-(3-chlorophenyl)-substituent, in that order, on the 6-phenylimidazo[2,1-b]thiazole impacts more positively than other aryl-substituents, on the anti-proliferative properties of these compounds.     

Stereoisomeric guaiacylglycerol-β-coniferyl aldehyde ether induces distinctive apoptosis by downregulation of MEK/ERK pathway in hepatocellular carcinoma cells

Two 8-O-4′-type neolignan epimers erythro-guaiacylglycerol-β-coniferyl aldehyde ether (1) and threo-guaiacylglycerol-β-coniferyl aldehyde ether (2) were isolated from the stems of Picrasma quassioides. Further chiral separation gave two pairs of enantiomers 1a/1b and 2a/2b. The cytotoxicity assay against hepatocellular carcinoma Hep3B and HepG2 cells was evaluated by MTT assay. The results showed that 1b (IC₅₀ = 45.56 μM) and 2b (IC₅₀ = 39.02 μM) had more cytotoxic effect than its enantiomers 1a (IC₅₀ = 82.66 μM) and 2a (IC₅₀ = 67.97 μM) in Hep3B cells, respectively. Moreover, 1b and 2b could induce more apoptotic cells as well as higher reactive oxygen species (ROS) generation than 1a and 2a at 50 μM. In addition, a further study on the phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways was investigated. The results revealed that all compounds had no significant effect on PI3K/AKT pathway, however, 1b and 2b attenuated the relative levels of p-MEK and p-ERK when compared with 1a and 2a. Taken together, the absolute configurations of guaiacylglycerol-β-coniferyl aldehyde ether had an impact on the inhibitory effect on Hep3B cells. The inactivation of MEK/ERK signaling pathway might contribute to apoptosis induction and ROS generation in 1b- and 2b-treated cells.     

Design and synthesis of pyrazolopyridine derivatives as sphingosine 1-phosphate receptor 2 ligands

Eleven new sphingosine 1-phosphate receptor 2 (S1PR2) ligands were synthesized by modifying lead compound N-(2,6-dichloropyridin-4-yl)-2-(4-isopropyl-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridin-6-yl)hydrazine-1-carboxamide (JTE-013) and their binding affinities toward S1PRs were determined in vitro using [³²P]S1P and cell membranes expressing recombinant human S1PRs. Among these ligands, 35a (IC₅₀?=?29.1?±?2.6?nM) and 35b (IC₅₀?=?56.5?±?4.0?nM) exhibit binding potency toward S1PR2 comparable to JTE-013 (IC₅₀?=?58.4?±?7.4?nM) with good selectivity for S1PR2 over the other S1PRs (IC₅₀?>?1000?nM). Further optimization of these analogues may identify additional and more potent and selective compounds targeting S1PR2.     

Synthesis and in vitro anticancer evaluation of some fused indazoles,quinazolines and quinolines as potential EGFR inhibitors

derivatives of benzo[g]indazole 5a, b, benzo[h]quinazoline 7, 12a-c, 13a-c and 15a-c and benzo[h]quinoline 17a-c and 19a-c were synthesized from 6-methoxy-3,4-dihydronaphthalen-1(2H)-one (1). Anticancer activity of all the synthesized compounds was evaluated against four cancerous cell lines; HepG2, MCF-7, HCT116 and Caco-2. MCF-7 cells emerged as the most sensitive cell line against the target compounds. All the examined compounds, except 5a and 5b, displayed potent to moderate anticancer activity against MCF-7 cells with an IC₅₀ values ranging from 7.21 to 21.55 µM. In particular, compounds 15c and 19b emerged as the most potent derivatives against EGFR-expressing MCF-7 cells with IC₅₀ values = 7.70 ± 0.39 and 7.21 ± 0.43 μM, respectively. Additionally, both compounds did not display any significant cytotoxicity towards normal BHK-21 fibroblast cells (IC₅₀ value > 200 µM), thereby providing a good safety profile as anticancer agents. Furthermore, compounds 15c and 19b displayed potent inhibitory activity towards EGFR in the sub-micromolar range (IC₅₀ = 0.13 ± 0.01 and 0.14 ± 0.01 μM, respectively), compared to that of Erlotinib (IC₅₀ = 0.11 ± 0.01 μM). Docking studies for 15c and 19b into EGFR active site was carried out to explore their potential binding modes. Therefore, compounds 15c and 19b can be considered as interesting candidates for further development of more potent anticancer agents.     

Design,synthesis and anticancer activity of N-(1-(4-(dibenzo[b,f][1,4]thiazepin-11-yl)piperazin-1-yl)-1-oxo-3-phenylpropan-2-yl derivatives

Novel N-(1-(4-(dibenzo[b,f][1,4]thiazepin-11-yl)piperazin-1-yl)-1-oxo-3-phenylpropan-2-yl derivatives were designed, synthesized and their chemical structures were confirmed by ¹H NMR, ¹³C NMR and Mass spectra. The anticancer activities of the newly synthesized compounds were evaluated in vitro against three human cancer cell lines including K562, Colo-205 and MDA-MB 231 by MTT assay. The screening results showed that five compounds (16b, 16d, 16i, 16p and 16q) exhibited potent cytotoxic activities with IC₅₀ values between 20 and 40 μM. Further in vitro studies revealed that inhibition of sirtuins could be the possible mechanism of action of these molecules.     

1,4-Dihydroquinazolin-3(2H)-yl benzamide derivatives as anti-inflammatory and analgesic agents with an improved gastric profile: Design,synthesis, COX-1/2 inhibitory activity and molecular docking study

The design and synthesis of a new series of 1,4-dihydroquinazolin-3(2H)-yl benzamide derivatives (4a–o) as anti-inflammatory and analgesic agents and COX-1/2 inhibitors are reported. The target compounds (4a–o) were synthesized using a two-step scheme, and their chemical structures were confirmed with ¹H NMR, ¹³C NMR, and mass spectra and elemental analysis. Compounds 4b, 4d, 4h, 4l, 4n and 4o showed the best in vitro COX-2 inhibitory activity (IC₅₀ 0.04–0.07 μM), which was nearly the same as that of the reference drug celecoxib (IC₅₀ 0.049 μM), but had a lower selectivity index, as dictated in our target design. In the in vivo anti-inflammatory inhibition assay, compounds 4b, 4c, 4e, 4f, 4m and 4o showed better oedema inhibition percentages, ranging from 38.1% to 54.1%, than did diclofenac sodium (37.8%). An in vivo analgesic assay revealed that compounds 4b and 4n had a potential analgesic effect 4- to 21-fold more potent than that of indomethacin and diclofenac sodium. All the tested compounds showed an improved ulcerogenic index when compared to indomethacin. In the synthesized series, compound 4b showed the best biological activity in all the experiments. The docking study results agreed with the in vitro COX inhibition assay results. Moreover, the predicted in silico studies of all the compounds support their potential as drug candidates.     

Anti-inflammatory drug approach: Synthesis and biological evaluation of novel pyrazolo[3,4-d]pyrimidine compounds

In this study, the acid chlorides of pyrazolo[3,4-d]pyrimidine compounds were prepared and reacted with a number of nucleophiles. The novel compounds were experimentally tested via enzyme assay and they showed cyclooxygenase-2 inhibition activity in the middle micro molar range (4b had a COX-1 IC₅₀ of 26 µM and a COX-2 IC₅₀ of 34 µM, 3b had a COX-1 IC₅₀ of 19 µM and a COX-2 IC₅₀ of 31 µM, 3a had a COX-2 IC₅₀ of 42 µM). These compounds were analyzed via docking and were predicted to interact with some of the COX-2 key residues. Our best hit, 4d (COX-1 IC₅₀ of 28 µM, COX-2 IC₅₀ of 23 µM), appears to adopt similar binding modes to the standard COX-2 inhibitor, celecoxib, proposing room for possible selectivity. Additionally, the resultant novel compounds were tested in several in vivo assays. Four compounds 3a (COX-2 IC₅₀ of 42 µM), 3d, 4d and 4f were notable for their anti-inflammatory activity that was comparable to that of the clinically available COX-2 inhibitor celecoxib. Interestingly, they showed greater potency than the famous non-steroidal anti-inflammatory drug, Diclofenac sodium. In summary, these novel pyrazolo[3,4-d]pyrimidine analogues showed interesting anti-inflammatory activity and could act as a starting point for future drugs.     

Design,synthesis and biological evaluation of 1H-pyrrolo[2,3-b]pyridine and 1H-pyrazolo[3,4-b]pyridine derivatives as c-Met inhibitors

Five novel 1H-pyrrolo[2,3-b]pyridine or 1H-pyrazolo[3,4-b]pyridine derivatives, with a methylene, sulfur, sulfoxide or cyclopropyl group as a linker, were designed, synthesized and biologically evaluated against c-Met and ALK. The development of these methods of compound synthesis may provide an important reference for the construction of novel 7-azaindole and 7-azaindazole derivatives with a single atom linker. The enzyme assay and cell assay in vitro showed that compound 9 displayed strong c-Met kinase inhibition with IC₅₀ of 22.8 nM, moderate ALK kinase inhibition, and strong cell inhibition with MKN-45 IC₅₀ of 329 nM and EBC-1 IC₅₀ of 479 nM. In order to find the better candidate compounds, compounds 8, 9 and 10 have been selected as tool compounds for further optimization.     

Design,synthesis, and structure–activity relationships of pyrimido[4,5-b]indole-4-amines as microtubule depolymerizing agents that are effective against multidrug resistant cells

To identify the structural features of 9H-pyrimido[4,5-b]indoles as microtubule depolymerizers, pyrimido[4,5-b]indoles 2–8 with varied substituents at the 2-, 4- and 5-positions were designed and synthesized. Nucleophilic displacement of 2,5-substituted-4-chloro-pyrimido[4,5-b]indoles with appropriate arylamines was the final step employed in the synthesis of target compounds 2–8. Compounds 2 and 6 had two-digit nanomolar potency (IC₅₀) against MDA-MB-435, SK-OV-3 and HeLa cancer cells in vitro. Compounds 2 and 6 also depolymerized microtubules comparable to the lead compound 1. Compounds 2, 3, 6 and 8 were effective in cells expressing P-glycoprotein or the βIII isotype of tubulin, mechanisms that are associated with clinical drug resistance to microtubule targeting drugs. Proton NMR and molecular modeling studies were employed to identify the structural basis for the microtubule depolymerizing activity of pyrimido[4,5-b]indoles.     

Discovery of novel tricyclic pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amine derivatives as VEGFR-2 inhibitors

In an effort to develop ATP-competitive VEGFR-2 selective inhibitors, a novel series of tricyclic pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amine derivatives were designed and synthesized. These compounds were characterized by IR, ¹H NMR, ¹³C NMR, elemental and mass spectral analyses. Docking studies have given a partial insight into the molecular determinants of the activity of this novel series in VEGFR-2 kinase active site. Moreover, these compounds were assessed at 10 μM for their selective inhibitory activities over a panel of 6 human kinases, namely VEGFR-1/Flt-1, VEGFR-2/KDR, EGFR, CDK5/p25, GSK3α and GSK3β. Compound N-(4,6-dimethylthieno[2,3-b]pyridine)-7,9-dimethylpyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amine (9d) exhibited the most potent and selective inhibitory activity against VEGFR-2/KDR over the six human kinases, with an IC₅₀ value 2.6 μM. The identification of this hit candidate could aid the design of new tricyclic-based VEGFR-2 kinase modulators.