Discovery of novel resorcinol diphenyl ether-based PROTAC-like molecules as dual inhibitors and degraders of PD-L1.

Novel resorcinol diphenyl ether-based PROTACs (PROteolysis TArgeting Chimeras) were designed and evaluated for their inhibitory activity against the programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) pathway and their ability to degrade PD-L1 protein. Most of the compounds displayed excellent inhibitory activities against PD-1/PD-L1, as assessed by the homogenous time-resolved fluorescence (HTRF) binding assay, with IC50 values ranging from 25 nM to 200 nM. Among them, compound P22 is one of the best with an IC50 value of 39.2 nM. In addition to inhibiting PD-1/PD-L1 interaction, P22 also significantly restored the immunity repressed in a co-culture model of Hep3B/OS-8/hPD-L1 and CD3 T cells. Furthermore, flow cytometry (FCM) and western-blot data demonstrated that P22 could moderately reduce the protein levels of PD-L1 in a lysosome-dependent manner, which may contribute to its immune effects. Preliminary FCM and western-blot data suggest that it is possible to build PD-L1-targeting PROTAC-like molecules based on PD-1/PD-L1 small molecule inhibitors, though these compounds showed only modest degradation efficiencies. Collectively, this work suggests that P22 may serve as a starting point for exploring the degradation of PD-L1 by PROTAC-like strategy.

Design, Synthesis, and Herbicidal Activity of Novel Diphenyl Ether Derivatives Containing Fast Degrading Tetrahydrophthalimide.

To seek new protoporphyrinogen oxidase (PPO) inhibitors with better biological activity, a series of novel diphenyl ether derivatives containing tetrahydrophthalimide were designed based on the principle of substructure splicing and bioisomerization. PPO inhibition experiments exhibited that 6c is the most potential compound, with the half-maximal inhibitory concentration (IC50) value of 0.00667 mg/L, showing 7 times higher activity than Oxyfluorfen (IC50 = 0.0426 mg/L) against maize PPO and similar herbicidal activities to Oxyfluorfen in weeding experiments in greenhouses and field weeding experiments. In view of the inspected bioactivities, the structure-activity relationship (SAR) of this series of compounds was also discussed. Crop selection experiments demonstrate that compound 6c is safe for soybeans, maize, rice, peanuts, and cotton at a dose of 300 g ai/ha. Accumulation analysis experiments showed that the accumulation of 6c in some crops (soybeans, peanuts, and cotton) was significantly lower than Oxyfluorfen. Current work suggests that compound 6c may be developed as a new herbicide candidate in fields.

Design, synthesis, in silico and in vitro evaluation of novel diphenyl ether derivatives as potential antitubercular agents.

Diphenyl ether derivatives inhibit mycobacterial cell wall synthesis by inhibiting an enzyme, enoyl-acyl carrier protein reductase (InhA), which catalyses the last step in the fatty acid synthesis cycle of genus Mycobacterium. To select and validate a protein crystal structure of enoyl-acyl carrier protein reductase of Mycobacterium tuberculosis for designing inhibitors using molecular modelling, a cross-docking and correlation study was performed. A series of novel 1-(3-(3-hydroxy-4-phenoxyphenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl) ethan-1-ones were synthesized from this model and screened for their antitubercular activity against M. tuberculosis H37Rv. Compound PYN-8 showed good antitubercular activity on M. tuberculosis H37Rv (MIC = 4-7 µM) and Mycobacterium bovis (% inhibition at 10 µM = 95.91%). Cytotoxicity of all the synthesized derivatives was assessed using various cell lines, and they were found to be safe. Structure of PYN-8 was also confirmed by single-crystal X-ray diffraction. The molecular modelling studies also corroborated the biological activity of the compounds. Further, in silico findings revealed that all these tested compounds exhibited good ADME properties and drug likeness and thus may be considered as potential candidates for further drug development.

Synthesis, Biological Evaluation and Molecular Dynamics Simulation Studies of Novel Diphenyl Ethers.

BACKGROUND: The well-known antibacterial agent Triclosan (TCL) that targets bacterial enoylacyl protein reductase has been described to inhibit human fatty acid synthase (FASN) via the enoylacyl reductase domain. A Literature survey indicates that TCL is selectively toxic to cancer cells and furthermore might indeed reduce cancer incidence in vivo. A recent study found that TCL inhibits FASN by acting as an allosteric protein-protein interface (PPI) inhibitor. It induces dimer orientation changes that effect in a downstream reorientation of catalytic residues in the NADPH binding site proposing TCL as a viable scaffold to design a superior molecule that might have more inhibitory potential. This unveils tons of potential interaction space to take advantage of future inhibitor design. OBJECTIVES: Synthesis of TCL mimicking novel diphenyl ether derivatives, biological evaluation as potential antiproliferative agents and molecular docking and molecular dynamics simulation studies. METHODS: A series of novel N-(1-(3-hydroxy-4-phenoxyphenyl)-3-oxo-3-phenylpropyl)acetamides (3a-n) and N-(3(3-hydroxy-4phenoxyphenyl)-3-oxo-1-phenylpropyl) acetamides (6a-n) were designed, synthesized, characterized and evaluated against HepG2, A-549, MCF-7 and Vero cell lines. The induction of antiproliferative activity of selected compounds (3d and 6c) was done by AO/EB (acridine orange/ethidium bromide) nuclear staining method, DNA fragmentation study, and cell cycle analysis was performed by flow cytometry. Molecular docking and dynamics simulation study was also performed. RESULTS: Among the tested compounds, compound 3d was most active (IC50 13.76 ± 0.43 µM) against A-549 cell line. Compounds 3d and 3g were found to be moderately active with IC50 30.56 ± 1.1 µM and 25.05 ± 0.8 µM respectively against MCF-7 cell line. Morphological analysis of A-549 cells treated with 3d and 6c clearly demonstrated the reduction of cell viability and induction of apoptosis. DNA fragmentation was observed as a characteristic of apoptosis in treated cells. Further, cell cycle analysis by flow cytometry confirmed that compounds 3d and 6c significantly arrested the cell cycle at the G0/G1 phase. Molecular docking study demonstrated that these compounds exhibit high affinity for the human fatty acid synthase (hFASN) target. Molecular dynamics simulation study of the most active compound 3d was performed for calculating binding free energies using Molecular Mechanics-Generalized Born Surface Area (MM/GBSA). CONCLUSION: Compound 3d (IC50 13.76 ± 0.43 µM) has been identified as a potential lead molecule for anticancer activity against A-549 cells followed by 3l, 6c, and 3g. Thus, the design of diphenyl ether derivatives with enhanced affinity to the binding site of hER may lead to the discovery of potential anticancer agents.

Potentials of Diphenyl Ether Scaffold as a Therapeutic Agent: A Review.

Diphenyl ethers (DPE) and its analogs have exhibited excellent potential for therapeutic and industrial applications. Since the 19th century, intensive research is perpetuating on the synthetic routes and biological properties of DPEs. Few well-known DPEs are Nimesulide, Fenclofenac, Triclosan, Sorafenib, MK-4965, and MK-1439 which have shown the potential of this moiety as a lead scaffold for different pharmacological properties. In this review, we recapitulate the diverse synthetic route of DPE moiety inclusive of merits and demerits over the classical synthetic route and how this moiety sparked an interest in researchers to discern the SAR (Structure Activity Relationship) for the development of diversified biological properties of DPEs such as antimicrobial, antifungal, antiinflammatory & antiviral activities.

Diphenyl ether derivatives occupy the expanded binding site of cyclohexanedione compounds at the colchicine site in tubulin by movement of the αT5 loop.

Microtubule targeting agents represent a very active arena in the development of anticancer agents. In particular, compounds binding at the colchicine site in tubulin are being deeply studied, and the structural information recently available on this binding site allows structure-directed design of new ligands. Structural comparison of our recently reported high resolution X-Ray structure of the cyclohexanedione derivative TUB075 bound to tubulin and the tubulin-DAMA-colchicine complex has revealed a conformational change in the αT5 loop. By a grid-based computational analysis of the tubulin-DAMA-colchicine binding site, we have identified a new favourable binding area in the colchicine-site that was unexplored by our lead TUB075. Thus, based on a structure-guided design, new cyclohexanedione derivatives have been synthesized and tested for tubulin binding and in cellular assays. As a result, we have identified diphenyl ether derivatives with IC50 values around 10-40 nM against three different tumor cell lines and affinity constants for tubulin similar to that of colchicine around 107 M-1. As expected, they halted the cell cycle progression at G2/M phase at concentrations as low as 0.08 µM.

[Design, synthesis and antiproliferative activity in cancer cells of novel dihydropyrazolyl and pyrazolyl artemisinin-phenyl ethers].

To explore potent anticancer agent based on artemisinin scaffold, a series of 10-O-phenyl ethers derivatives containing dihydropyrazolyl or pyrazolyl moiety have been designed and synthesized. Their structures were determined by LC-MS and ¹H-NMR date. Inhibitory effects of the target compounds in human breast cancer MCF-7, MCF/Adr, MDA-MB-231 cells and prostate cell line PC-3 were determined by MTT assay. Those derivatives displayed good antiproliferative activity against the tested cancer cells. Particularly, target compounds exhibited significant cytotoxicity against drug-resistance cells MCF/Adr, which was worthy for further investigation.

Phosphorogenic sensors for biothiols derived from cyclometalated iridium(III) polypyridine complexes containing a dinitrophenyl ether moiety.

We report the synthesis and characterization of three cyclometalated iridium(III) polypyridine complexes containing a 2,4-dinitrophenyl ether moiety [Ir(pq)2(N^N)](PF6) (Hpq=2-phenylquinoline; N^N=4-(N-(4-(2,4-dinitrophenoxy)benzyloxy)carbonyl)aminomethyl-4'-methyl-2,2'-bipyridine (bpy-dinitro-1) (1a), 4-(2,4-dinitrophenoxy)methyl-4'-methyl-2,2'-bipyridine (bpy-dinitro-2) (2a), 4-(4-(2,4-dinitrophenoxy)phenyl)-2,2'-bipyridine (bpy-dinitro-3) (3a)) as intracellular sensors for biothiols. Due to the quenching effect of the dinitroaromatic moiety, these complexes were extremely weakly emissive. Upon the reaction with biothiols, however, the emission was turned on as a consequence of the departure of the quenching unit. The results from a range of experiments demonstrated that complex 1a was noncytotoxic under the conditions used for confocal imaging, showed facile cellular uptake, and can serve as a phosphorogenic intracellular sensor for biothiols including glutathione (GSH) and hydrogen sulfide.

Discovery of Clinical Candidate 4-[2-(5-Amino-1H-pyrazol-4-yl)-4-chlorophenoxy]-5-chloro-2-fluoro-N-1,3-thiazol-4-ylbenzenesulfonamide (PF-05089771): Design and Optimization of Diaryl Ether Aryl Sulfonamides as Selective Inhibitors of NaV1.7.

A series of acidic diaryl ether heterocyclic sulfonamides that are potent and subtype selective NaV1.7 inhibitors is described. Optimization of early lead matter focused on removal of structural alerts, improving metabolic stability and reducing cytochrome P450 inhibition driven drug-drug interaction concerns to deliver the desired balance of preclinical in vitro properties. Concerns over nonmetabolic routes of clearance, variable clearance in preclinical species, and subsequent low confidence human pharmacokinetic predictions led to the decision to conduct a human microdose study to determine clinical pharmacokinetics. The design strategies and results from preclinical PK and clinical human microdose PK data are described leading to the discovery of the first subtype selective NaV1.7 inhibitor clinical candidate PF-05089771 (34) which binds to a site in the voltage sensing domain.

A 4-Phenoxyphenol Derivative Exerts Inhibitory Effects on Human Hepatocellular Carcinoma Cells through Regulating Autophagy and Apoptosis Accompanied by Downregulating α-Tubulin Expression.

Hepatocellular carcinoma (HCC) is a leading cancer worldwide. Advanced HCCs are usually resistant to anticancer drugs, causing unsatisfactory chemotherapy outcomes. In this study, we showed that a 4-phenoxyphenol derivative, 4-[4-(4-hydroxyphenoxy)phenoxy]phenol (4-HPPP), exerts an inhibitory activity against two HCC cell lines, Huh7 and Ha22T. We further investigated the anti-HCC activities of 4-HPPP, including anti-proliferation and induction of apoptosis. Our results showed that higher dosage of 4-HPPP downregulates the expression of α-tubulin and causes nuclear enlargement in both the Huh-7 and Ha22T cell lines. Interestingly, the colony formation results showed a discrepancy in the inhibitory effect of 4-HPPP on HCC and rat liver epithelial Clone 9 cells, suggesting the selective cytotoxicity of 4-HPPP toward HCC cells. Furthermore, the cell proliferation and apoptosis assay results illustrated the differences between the two HCC cell lines. The results of cellular proliferation assays, including trypan blue exclusion and colony formation, revealed that 4-HPPP inhibits the growth of Huh7 cells, but exerts less cytotoxicity in Ha22T cells. Furthermore, the annexin V assay performed for detecting the apoptosis showed similar results. Western blotting results showed 4-HPPP caused the increase of pro-apoptotic factors including cleaved caspase-3, Bid and Bax in HCC cells, especially in Huh-7. Furthermore, an increase of autophagy-associated protein microtubule-associated protein-1 light chain-3B (LC3B)-II and the decrease of Beclin-1 and p62/SQSTM1 were observed following 4-HPPP treatment. Additionally, the level of γH2A histone family, member X (γH2AX), an endogenous DNA damage biomarker, was dramatically increased in Huh7 cells after 4-HPPP treatment, suggesting the involvement of DNA damage pathway in 4-HPPP-induced apoptosis. On the contrary, the western blotting results showed that treatment up-regulates pro-survival proteins, including the phosphorylation of protein kinase B (Akt) and the level of survivin on Ha22T cells, which may confer a resistance toward 4-HPPP. Notably, the blockade of extracellular signal-regulated kinases (ERK), but not Akt, enhanced the cytotoxicity of 4-HPPP against Ha22T cells, indicating the pro-survival role of ERK in 4-HPPP-induced anti-HCC effect. Our present work suggests that selective anti-HCC activity of 4-HPPP acts through induction of DNA damage. Accordingly, the combination of ERK inhibitor may significantly enhance the anti-cancer effect of 4-HPPP for those HCC cells which overexpress ERK in the future.

Comparison of Properties among Dendritic and Hyperbranched Poly(ether ether ketone)s and Linear Poly(ether ketone)s.

Poly(ether ether ketone) dendrimers and hyperbranched polymers were prepared from 3,5-dimethoxy-4'-(4-fluorobenzoyl)diphenyl ether and 3,5-dihydroxy-4'-(4-fluorobenzoyl)diphenyl ether through aromatic nucleophilic substitution reactions. 1-(tert-Butyldimethylsiloxy)-3,5-bis(4-fluorobenzoyl)benzene was polycondensed with bisphenols, followed by cleavage of the protective group to form linear poly(ether ketone)s having the same hydroxyl groups in the side chains as the chain ends of the dendrimer and hyperbranched polymers. Their properties, such as solubilities, reduced viscosities, and thermal properties, were compared with one another. Similar comparisons were also carried out among the corresponding methoxy group polymers, and the size of the molecules was shown to affect the properties.

Chemistry and Pharmacology of a Series of Unichiral Analogues of 2-(2-Pyrrolidinyl)-1,4-benzodioxane, Prolinol Phenyl Ether, and Prolinol 3-Pyridyl Ether Designed as α4ß2-Nicotinic Acetylcholine Receptor Agonists.

Some unichiral analogues of 2R,2'S-2-(1'-methyl-2'-pyrrolidinyl)-7-hydroxy-1,4-benzodioxane, a potent and selective α4ß2-nAChR partial agonist, were designed by opening dioxane and replacing hydroxyl carbon with nitrogen. The resulting 3-pyridyl and m-hydroxyphenyl ethers have high α4ß2 affinity and good subtype selectivity, which get lost if OH is removed from phenyl or the position of pyridine nitrogen is changed. High α4ß2 affinity and selectivity are also attained by meta hydroxylating the 3-pyridyl and the phenyl ethers of (S)-N-methylprolinol and the phenyl ether of (S)-2-azetidinemethanol, known α4ß2 agonists, although the interaction mode of the aryloxymethylene substructure cannot be assimilated to that of benzodioxane. Indeed, the α4ß2 and α3ß4 functional tests well differentiate behaviors that the binding tests homologize: both the 3-hydroxyphenyl and the 5-hydroxy-3-pyridyl ether of N-methylprolinol are α4ß2 full agonists, but only the latter is highly α4ß2/α3ß4 selective, while potent and selective partial α4ß2 agonism characterizes the hydroxybenzodioxane derivative and its two opened semirigid analogues.

A convenient method for the synthesis of (prop-2-ynyloxy)benzene derivatives via reaction with propargyl bromide, their optimization, scope and biological evaluation.

A highly convenient method has been developed for the synthesis of (prop-2-ynyloxy) benzene and its derivatives. Differently substituted phenol and aniline derivatives were allowed to react with propargyl bromide in the presence of K2CO3 base and acetone as solvent. The compounds were synthesized in good yields (53-85%). Low cost, high yields and easy availability of compounds helped in the synthesis. Electron withdrawing groups favor the formation of stable phenoxide ion thus in turn favors the formation of product while electron donating groups do not favor the reaction. Phenol derivatives gave good yields as compared to that of aniline. As aprotic polar solvents favor SN2 type reactions so acetone provided best solvation for the reactions. K2CO3 was proved to be good for the synthesis. Antibacterial, Antiurease and NO scavenging activity of synthesized compounds were also examined. 4-bromo-2-chloro-1-(prop-2-ynyloxy)benzene 2a was found most active compound against urease enzyme with a percentage inhibition of 82.00±0.09 at 100 µg/mL with IC50 value of 60.2. 2-bromo-4-methyl-1-(prop-2-ynyloxy)benzene 2d was found potent antibacterial against Bacillus subtillus showing excellent inhibitory action with percentage inhibition of 55.67±0.26 at 100 µg/ml wih IC50 value of 79.9. Based on results, it can be concluded that some of the synthesized compounds may have potential antiurease and antibacterial effects against several harmful substances.

Poly-guanidinoethylphenylethers organised around a benzene ring: synthesis and evaluation of their antibacterial and cytotoxic properties.

A new family of poly-guanidinium species with a benzene core as the organising agent has been developed. Their antibacterial properties have been evaluated against reference Gram positive and Gram negative bacteria, and their cytotoxicity against eukaryotic cells. Most of these compounds exhibited Minimum Inhibitory Concentrations in the micromolar range.

Synthesis and biological evaluation of 3-phenethylazetidine derivatives as triple reuptake inhibitors.

We report the synthesis of 3-phenethylazetidine derivatives 2 and their biological activities against 5-HT, NE and DA transporters as well as microsomal stability, CYP inhibition, and hERG inhibition profiles. Compound 2at showed most potent triple reuptake inhibitor with good selectivity as a candidate for depression.

Synthesis and evaluation of a novel class Hsp90 inhibitors containing 1-phenylpiperazine scaffold.

Previously, we identified 1-(2-(4-bromophenoxy)ethoxy)-3-(4-(2-methoxyphenyl)piperazin-1-yl)propan-2-ol (1) as a novel Hsp90 inhibitor with moderate activity through virtual screening. In this study, we report the optimization process of 1. A series of analogues containing the 1-phenylpiperazine core scaffold were synthesized and evaluated. The structure-activity relationships (SAR) for these compounds was also discussed for further molecular design. This effort afforded the most active inhibitor 13f with improved activity in not only target-based level, but also cell-based level compared with the original hit 1.

4,4'-Diaminodiphenyl ether derivatives: synthesis, spectral, optical, thermal characterization and in-vitro cytotoxicity against Hep 3B and IMR 32 human cell lines.

4,4'-Diaminodiphenyl ether was selected as a lead compound to prepare a novel series of bisimine derivatives bearing polyaromatic hydrocarbon substituents and their reduced benzyl forms. The new compounds were structurally characterized by microanalysis, mass, IR, (1)H, (13)C, DEPT-135, HSQC, g-COSY NMR spectroscopy, UV-visible, fluorescence spectrophotometers and by thermogravimetric analysis. The antitumor activity of these derivatives was evaluated in-vitro against Hep 3B and IMR 32 by the MTT assay and the results were compared with cisplatin. Interestingly, some compounds were found extremely active against both the cell lines and proved to be more potent as cytotoxic agents than cisplatin. Morphological evidences suggest the induction of apoptosis and explain the mode of action of these derivatives as antitumor agents.

Modulation of cyclins, p53 and mitogen-activated protein kinases signaling in breast cancer cell lines by 4-(3,4,5-trimethoxyphenoxy)benzoic acid.

Despite the advances in cancer therapy and early detection, breast cancer remains a leading cause of cancer-related deaths among females worldwide. The aim of the current study was to investigate the antitumor activity of a novel compound, 4-(3,4,5-trimethoxyphenoxy)benzoic acid (TMPBA) and its mechanism of action, in breast cancer. Results indicated the relatively high sensitivity of human breast cancer cell-7 and MDA-468 cells towards TMPBA with IC50 values of 5.9 and 7.9 µM, respectively compared to hepatocarcinoma cell line Huh-7, hepatocarcinoma cell line HepG2, and cervical cancer cell line Hela cells. Mechanistically, TMPBA induced apoptotic cell death in MCF-7 cells as indicated by 4',6-diamidino-2-phenylindole (DAPI) nuclear staining, cell cycle analysis and the activation of caspase-3. Western blot analysis revealed the ability of TMPBA to target pathways mediated by mitogen-activated protein (MAP) kinases, 5' adenosine monophosphate-activated protein kinase (AMPK), and p53, of which the concerted action underlined its antitumor efficacy. In addition, TMPBA induced alteration of cyclin proteins' expression and consequently modulated the cell cycle. Taken together, the current study underscores evidence that TMPBA induces apoptosis in breast cancer cells via the modulation of cyclins and p53 expression as well as the modulation of AMPK and mitogen-activated protein kinases (MAPK) signaling. These findings support TMPBA's clinical promise as a potential candidate for breast cancer therapy.

Synthesis and antiprotozoal activities of benzyl phenyl ether diamidine derivatives.

Sixty-two cationic benzyl phenyl ether derivatives (36 amidines and 26 prodrugs) were prepared and assayed for activities in vitro and in vivo against Trypanosoma brucei rhodesiense (STIB900), and in vitro against Plasmodium falciparum (K1) and Leishmania donovani axenic amastigotes. 3-Amidinobenzyl 4-amidino-2-iodo-6-methoxyphenyl ether dihydrochloride (55, IC50 = 3.0 nM) and seven other compounds exhibited IC50 values below 10 nM against T. b. rhodesiense in vitro. The 2-bromo-4,4'-diamidino analogue 19 (IC50 = 4.0 nM) and 12 other analogues were more potent than pentamidine (IC50 = 46 nM) against P. falciparum. The 3',4-diamidino-2,6-diiodo analogue 49 (IC50 = 1.4 µM) and two other compounds were more effective than pentamidine (IC50 = 1.8 µM) against L. donovani. A prodrug, 3',4-bis(N″-methoxy)amidino-2-bromo derivative 38, was the most efficacious against trypanosome infected mice, attaining 4/4 cures in four daily 25 mg/kg oral doses, and the 2-chloro-4,4'-diamidine 18 cured 3/4 mice in four daily 5 mg/kg intraperitoneal doses.

Preparation of 1,3-bis(allyloxy)benzene under a new multi-site phase-transfer catalyst combined with ultrasonication--a kinetic study.

In the present work, kinetics of synthesis of 1,3-bis(allyloxy)benzene was successfully carried out by O-allylation of resorcinol with allyl bromide using aqueous potassium hydroxide and catalyzed by a new multi-site phase-transfer catalyst viz., 1,3,5,7-tetrabenzylhexamethylenetetraammonium tetrachloride, MPTC under ultrasonic (40 kHz, 300 W) assisted organic solvent condition. The pseudo first-order kinetic equation was applied to describe the overall reaction. Under ultrasound irradiation (40 kHz, 300 W) in a batch reactor, it shows that the overall reaction rate can be greatly enhanced to seven fold faster with ultrasound irradiation than without ultrasound. The present study provides a method to synthesize ethers by ultrasound assisted liquid-liquid phase-transfer catalysis condition.