Design,synthesis and antimalarial activity of novel bis{N-[(pyrrolo[1,2-a]quinoxalin-4-yl)benzyl]-3-aminopropyl}amine derivatives

Novel series of bis- and tris-pyrrolo[1,2-a]quinoxaline derivatives 1 were synthesized and tested for in vitro activity upon the intraerythrocytic stage of W2 and 3D7 Plasmodium falciparum strains. Biological results showed good antimalarial activity with IC₅₀ in the μM range. In attempting to investigate the large broad-spectrum antiprotozoal activities of these new derivatives, their properties toward Leishmania donovani were also investigated and revealed their selective antiplasmodial profile. In parallel, the in vitro cytotoxicity of these molecules was assessed on the human HepG2 cell line. Structure–activity relationships of these new synthetic compounds are discussed here. The bis-pyrrolo[1,2-a]quinoxalines 1n and 1p were identified as the most potent antimalarial candidates with selectivity index (SI) of 40.6 on W2 strain, and 39.25 on 3D7 strain, respectively. As the telomeres of the parasite could constitute an attractive target, we investigated the possibility of targeting Plasmodium telomeres by stabilizing the Plasmodium telomeric G-quadruplexes through a FRET melting assay by our new compounds.     

Synthesis and antibacterial activity of a new series of 3-[3-(substituted phenyl)-1-phenyl-1H-pyrazol-5-yl]-2H-chromen-2-one derivatives

A series of 3-[3-(substituted phenyl)-1-phenyl-1H-pyrazol-5-yl]-2H-chromen-2-one (4a–k) were synthesized by reaction of 3-[2,3-dibromo-3-(substituted phenyl)propanoyl]-2H-chromen-2-one (3 a-k) with phenyl hydrazine in presence of triethylamine in absolute ethanol, characterized by spectral data and screened for their in vitro antibacterial activity against gram-positive and gram-negative bacteria. Among the series, compounds 4d, 4h and 4i displayed an encouraging antibacterial activity profile as compared to reference standard drug ciprofloxacin against tested bacterial strains.     

Effects of Methylglyoxal bis(Guanylhydrazone) on Trypanosomatid Flagellates: Inhibition of Growth and Nucleoside Incorporation in Trypanosoma brucei*

SYNOPSIS. Methylglyoxal bis(guanylhydrazone) (MGBG) at 0.5 mm had little effect in vitro on Blastocrithidia culicis, Crithidia oncopelti, and Leishmania spp., but completely inhibited growth of Trypanosoma brucei. Inhibition became irreversible after a 3-h exposure of T. brucei culture procyclics. Treated organisms remained motile, but failed to divide. Polyamines, spermidine, and spermine, did not reverse the anti-trypanosome action of MGBG (preloading of cells or concurrent administration). Two intraperitoneal injections of the drug at a concentration of 50 mg kg body weight at a 1-day interval greatly reduced the parasitemia of T. brucei and T. congolense in rats. Trypanosome infections, however, relapsed and killed the animals in 6 days after treatment. It was evident from the results of tracer experiments with T. brucei that MGBG significantly lowered incorporation of [³H]thymidine by culture procyclics and of [³H]uridine by bloodstream forms; in both stages [³H]leucine incorporation was only slightly inhibited. It is suggested that MGBG interferes with nucleoside incorporation by Trypanosoma and that its mode of action is different in bloodstream and culture procyclics.     

Asymmetric biocatalytic reduction of 3,5-bis(trifluoromethyl) acetophenone to (<Emphasis Type="Italic">1R</Emphasis>)-[3,5-bis(trifluoromethyl)phenyl] ethanol using whole cells of newly isolated <Emphasis Type="Italic">Leifsonia xyli</Emphasis> HS0904

A novel bacterial strain HS0904 was isolated from a soil sample using 3,5-bis(trifluoromethyl) acetophenone as the sole carbon source. This bacterial isolate can asymmetrically reduce 3,5-bis(trifluoromethyl) acetophenone to (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol with high enantiometric excess (ee) value. Based on its morphological, physiological characteristics, Biolog, 16S rDNA sequence and phylogenetic analysis, strain HS0904 was identified as Leifsonia xyli HS0904. To our knowledge, this is the first reported case on the species L. xyli exhibited R-stereospecific carbonyl reductase and used for the preparation of chiral (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol. The optimization of parameters for microbial transformation of 3,5-bis(trifluoromethyl) acetophenone to (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol catalyzed by whole cells of L. xyli HS0904 was carried out by examining some key factors including buffer pH, reaction temperature, shaking speed, substrate concentration, and reaction time. The obtained optimized conditions for the bioreduction are as follows: buffer pH 8.0, 70 mM of 3,5-bis(trifluoromethyl) acetophenone, 100 g l⁻¹ of glucose as co-substrate, 200 g l⁻¹ of resting cells as biocatalyst, reaction for 30 h at 30 °C and 200 rpm. Under above conditions, 99.4% of product ee and best yield of 62% were obtained, respectively. The results indicated that isolate L. xyli HS0904 is a novel potential biocatalyst for the production of (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol.     

Efficient biocatalytic synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol by a newly isolated Trichoderma asperellum ZJPH0810 using dual cosubstrate: ethanol and glycerol

(R)-[3,5-bis(trifluoromethyl)phenyl] ethanol is a crucial intermediate for the synthesis of Aprepitant. An efficient biocatalytic process for (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol was developed via the asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone, catalyzed by whole cells of newly isolated Trichoderma asperellum ZJPH0810 using ethanol and glycerol as dual cosubstrate for cofactor recycling. A fungal strain ZJPH0810, showing asymmetric biocatalytic activity of 3,5-bis(trifluoromethyl) acetophenone to its corresponding (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol, was isolated from a soil sample. Based on its morphological and physiological characteristics and internal transcribed spacer sequence, this isolate was identified as T. asperellum ZJPH0810, which afforded an NADH-dependent (R)-stereospecific carbonyl reductase and was a promising biocatalyst for the synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol. Some key reaction parameters involved in the bioreduction catalyzed by T. asperellum ZJPH0810 were subsequently optimized. The effectiveness of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol production was significantly enhanced by employing a novel dual cosubstrate-coupled system for cofactor recycling. The established efficient bioreduction system contained 50 mM of 3,5-bis(trifluoromethyl) acetophenone and 60 g l^?1 of resting cells, employing ethanol (6.0 %, v/v) and glycerol (0.5 %, v/v) as dual cosubstrate. The bioreduction was performed in distilled water medium, at 30 °C and 200 rpm. Under the above conditions, a best yield of 93.4 % was obtained, which is nearly a 3.5-fold increase in contrast to no addition of cosubstrate. The ee value of the product reached above 98 %. This biocatalytic process shows great potential in the production of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol, a valuable chiral building block in the pharmaceutical industry.     

Synthesis of 5-enamine-4-thiazolidinone derivatives with trypanocidal and anticancer activity

A series of novel 2-(5-aminomethylene-4-oxo-2-thioxothiazolidin-3-yl)-3-phenylpropionic acid ethyl esters has been synthesized. Target compounds were evaluated for their trypanocidal activity towards Trypanosoma brucei brucei and Trypanosoma brucei gambiense. Several hit-compounds (8, 10, 12) inhibited growth of the parasites at sub-micromolar concentrations (IC₅₀ 0.027–1.936 µM) and showed significant selectivity indices (SI = 108–1396.2) being non-toxic towards the human primary fibroblasts. The screening of anticancer activity in vitro within NCI DTP protocol allowed to identify active 2-(5-{[5-(2,4-dichlorobenzyl)-thiazol-2-ylamino]-methylene}-4-oxo-2-thioxothiazolidin-3-yl)-3-phenylpropionic acid ethyl ester 14 that demonstrated inhibition against all 59 human tumor cell lines with the average GI₅₀ value of 2.57 μM. It was established that the activity type (antitrypanosomal or anticancer) as well as its level depends on the character of enamine fragment in the C5 position of thiazolidinone core.     

2,4-Diaminopyrimidines as potent inhibitors of Trypanosoma brucei and identification of molecular targets by a chemical proteomics approach

Background

There is an urgent need to develop new, safe and effective treatments for human African trypanosomiasis (HAT) because current drugs have extremely poor safety profiles and are difficult to administer. Here we report the discovery of 2,4-diaminopyrimidines, exemplified by 4-[4-amino-5-(2-methoxy-benzoyl)-pyrimidin-2-ylamino]-piperidine-1-carboxylic acid phenylamide (SCYX-5070), as potent inhibitors of Trypanosoma brucei and the related trypanosomatid protozoans Leishmania spp.

Methodology/Principal Findings

In this work we show that loss of T. brucei viability following SCYX-5070 exposure was dependent on compound concentration and incubation time. Pulse incubation of T. brucei with SCYX-5070 demonstrates that a short period of exposure (10–12 hrs) is required to produce irreversible effects on survival or commit the parasites to death. SCYX-5070 cured an acute trypanosomiasis infection in mice without exhibiting signs of compound related acute or chronic toxicity. To identify the molecular target(s) responsible for the mechanism of action of 2,4-diaminopyrimidines against trypanosomatid protozoa, a representative analogue was immobilized on a solid matrix (sepharose) and used to isolate target proteins from parasite extracts. Mitogen-activated protein kinases (MAPKs) and cdc2-related kinases (CRKs) were identified as the major proteins specifically bound to the immobilized compound, suggesting their participation in the pharmacological effects of 2,4-diaminopyrimidines against trypanosomatid protozoan parasites.

Conclusions/Significance

Results show that 2,4-diaminopyrimidines have a good in vitro and in vivo pharmacological profile against trypanosomatid protozoans and that MAPKs and CRKs are potential molecular targets of these compounds. The 2,4-diminipyrimidines may serve as suitable leads for the development of novel treatments for HAT.     

Phenyl and Diaryl Ureas with Thiazolo[5,4‐d]pyrimidine Scaffold as Angiogenesis Inhibitors: Design,Synthesis and Biological Evaluation

Angiogenesis is crucial for tumor growth and inhibition of angiogenesis has been regarded as a promising approach for cancer therapy. Vascular endothelial growth factor receptor‐2 (VEGFR‐2) is an important factor in angiogenesis. In this work, a novel series of thiazolo[5,4‐d]pyrimidine derivatives inhibiting angiogenesis were rationally designed and synthesized. Their inhibitory activities against human umbilical vein endothelial cells (HUVEC) were investigated in vitro. 1‐(4‐Fluorophenyl)‐3‐{4‐[(5‐methyl‐2‐phenyl[1,3]thiazolo[5,4‐d]pyrimidin‐7‐yl)amino]phenyl}urea ( 19b ) and 1‐(3‐Fluorophenyl)‐3‐{4‐[(5‐methyl‐2‐phenyl[1,3]thiazolo[5,4‐d]pyrimidin‐7‐yl)amino]phenyl}urea ( 19g ) exhibited the most potent inhibitory effect on HUVEC proliferation (IC₅₀=12.8 and 5.3 μm , respectively). Compound 19g could inhibit the migration of human umbilical vein endothelial cells. These results support the further investigation of these compounds as potent anticancer agents.     

2- and 3-[(Aryl)(azolyl)methyl]indoles as Potential Non-steroidal Aromatase Inhibitors

The present study was designed to follow our pharmacomodulation work in the field of non-steroidal aromatase inhibitors. All target compounds 12a–h and 28a–h were tested in vitro for human placental aromatase inhibition, using testosterone or androstenedione as the substrate for the aromatase enzyme and the IC₅₀ and relative potency to aminoglutethimide data are included. A SAR study indicated that 3-[(4-fluorophenyl)(1H-imidazol-1-yl)methyl]-1-ethyl-2-methyl-1H-indole (28?g) was a highly potent and selective aromatase inhibitor with IC₅₀ value of 0.025?μM. 28?g was also a weak inhibitor of androstenedione synthesis.     

Discovery of 2-(1H-imidazo-2-yl)piperazines as a new class of potent and non-cytotoxic inhibitors of Trypanosoma brucei growth in vitro

The identification of a new series of growth inhibitors of Trypanosoma brucei rhodesiense, causative agent of Human African Trypanosomiasis (HAT), is described. A selection of compounds from our in-house compound collection was screened in vitro against the parasite leading to the identification of compounds with nanomolar inhibition of T. brucei growth. Preliminary SAR on the hit compound led to the identification of compound 34 that shows low nanomolar parasite growth inhibition (T. brucei EC₅₀ 5?nM), is not cytotoxic (HeLa CC₅₀?>?25,000?nM) and is selective over other parasites, such as Trypanosoma cruzi and Plasmodium falciparum (T. cruzi EC₅₀ 8120?nM, P. falciparum EC₅₀ 3624?nM).     

Synthesis and in vitro antitubercular activity of some 1-[(4-sub)phenyl]-3-(4-{1-[(pyridine-4-carbonyl)hydrazono]ethyl}phenyl)thiourea

Various isonicotinyl hydrazones were prepared by reacting isonicotinyl hydrazide [INH] with 1-(4-acetylphenyl)-3-[(4-sub)phenyl]thiourea and were tested for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv and INH-resistant M. tuberculosis using the BACTEC 460 radiometric system. Among the synthesized compounds, 1-(4-fluorophenyl)-3-(4-{1-[(pyridine-4-carbonyl)-hydrazono]ethyl}phenyl)thiourea (4d) was found to be the most potent compound with a minimum inhibitory concentration of 0.49 microM against M. tuberculosis H37Rv and INH-resistant M. tuberculosis. When compared to INH, 4d was found to be 3 and 185 times more active against M. tuberculosis H37Rv and INH-resistant M. tuberculosis, respectively, with a selectivity index of >300.     

Alkynamide phthalazinones as a new class of TbrPDEB1 inhibitors

Several 3′,5′-cyclic nucleotide phosphodiesterases (PDEs) have been validated as good drug targets for a large variety of diseases. Trypanosoma brucei PDEB1 (TbrPDEB1) has been designated as a promising drug target for the treatment of human African trypanosomiasis. Recently, the first class of selective nanomolar TbrPDEB1 inhibitors was obtained by targeting the parasite specific P-pocket. However, these biphenyl-substituted tetrahydrophthalazinone-based inhibitors did not show potent cellular activity against Trypanosoma brucei (T. brucei) parasites, leaving room for further optimization. Herein, we report the discovery of a new class of potent TbrPDEB1 inhibitors that display improved activities against T. brucei parasites. Exploring different linkers between the reported tetrahydrophthalazinone core scaffold and the amide tail group resulted in the discovery of alkynamide phthalazinones as new TbrPDEB1 inhibitors, which exhibit submicromolar activities versus T. brucei parasites and no cytotoxicity to human MRC-5 cells. Elucidation of the crystal structure of alkynamide 8b (NPD-048) bound to the catalytic domain of TbrPDEB1 shows a bidentate interaction with the key-residue Gln874 and good directionality towards the P-pocket. Incubation of trypanosomes with alkynamide 8b results in an increase of intracellular cAMP, validating a PDE-mediated effect in vitro and providing a new interesting compound series for further studies towards selective TbrPDEB1 inhibitors with potent phenotypic activity.     

Discovery of a quinoline-based phenyl sulfone derivative as an antitrypanosomal agent

A series of natural products-based phenyl sulfone derivative and their property-based analogues were investigated as potential growth inhibitors of Trypanosoma brucei. Trypanosoma brucei is a kinetoplastid protozoan parasite that causes trypanosomiasis. In this work, we found that nopol- and quinoline-based phenyl sulfone derivative were the most active and selective for T. brucei, and they were not reactive towards the active thiol of T. brucei’s cysteine protease rhodesain. A thiol reactive variant of the quinoline-based phenyl sulfone was subsequently investigated and found to be a moderate inhibitor of rhodesain. The quinoline-based compound that is not reactive towards rhodesain can serve a template for phenotypic-based lead discovery while its thiol-active congener can serve as template for structure-based investigation of new antitrypanosomal agents.     

Design,synthesis and bioevaluation of novel umbelliferone analogues as potential mushroom tyrosinase inhibitors

Abstract

A series of umbelliferone analogues were synthesized and their inhibitory effects on the DPPH and mushroom tyrosinase were evaluated. The results showed that some of the synthesized compounds exhibited significant mushroom tyrosinase inhibitory activities. Especially, 2-oxo-2-[(2-oxo-2H-chromen-7-yl)oxy]ethyl-2,4-dihydroxybenzoate (4e) bearing 2,4-dihydroxy substituted phenyl ring exhibited the most potent tyrosinase inhibitory activity with IC₅₀ value 8.96?µM and IC₅₀ value of kojic acid is 16.69. The inhibition mechanism analyzed by Lineweaver–Burk plots revealed that the type of inhibition of compound 4e on tyrosinase was non-competitive. The docking study against tyrosinase enzyme was also performed to determine the binding affinity of the compounds. The compounds 4c and 4e showed the highest binding affinity with active binding site of tyrosinase. The initial structure activity relationships (SARs) analysis suggested that further development of such compounds might be of interest. The statistics of our results endorses that compounds 4c and 4e may serve as a structural template for the design and development of novel tyrosinase inhibitors.     

Design and synthesis of 3-[(7-chloro-1-oxidoquinolin-4-ylamino)alkyl]-1,3-thiazolidin-4-ones as antimalarial agents

A new series of quinoline analogs have been synthesized and found active against P. falciparum in vitro and P. yoelli in vivo. Compounds 8, 10 and 11 exhibited superior in vitro activity compared to chloroquine. Selected compounds 8, 10 and 11 exhibited significant suppression of parasitaemia in vivo assay. These analogs form a complex with hematin and inhibit the β-hematin formation, suggesting that this class of compounds act on a heme polymerization target. Further this study confirms that quinoline ring nitrogen is essential for both transportation of the molecule across the membrane as well as for tight binding to hematin.     

Synthesis,Antimicrobial Activities,and Molecular Docking Studies of Dihydrotriazine Derivatives Bearing a Quinoline Moiety

In this article, three series of dihydrotriazine derivatives bearing a quinoline moiety ( 5a , 5b , 8a – 8c , and 9a – 9m ) have been designed, synthesized, and evaluated as antibacterial agents. Compounds 8a – 8c were found to be the most potent of all of the compounds tested with an MIC value of 1 μg/mL against several Gram‐positive (S. aureus 4220 and MRSA CCARM 3506) and Gram‐negative (E. coli 1924) strains of bacteria. In addition, 3‐[4‐amino‐6‐(phenethylamino)‐2,5‐dihydro‐1,3,5‐triazin‐2‐yl)‐6‐[(3‐chlorobenzyl)oxy]quinolin‐2‐ol ( 8a ) showed potent inhibitory activity (MIC=2 μg/mL) against Pseudomonas aeruginosa 2742, indicating that its antibacterial spectrum is similar to those of the positive controls gatifloxacin and moxifloxacin. Structure‐activity relationships (SAR) analyses and docking studies implicated the dihydrotriazine group in increasing the antimicrobial potency of the quinoline compounds. In vitro enzyme study implied that compound 8a also displayed DHFR inhibition.     

Dual neurokinin NK(1)/NK(2) antagonists: N-[(R,R)-(E)-1-arylmethyl-3-(2-oxo-azepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamides and 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-arylmethyl-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamides.

Based on the structure of N-[(R,R)-(E)-1-(4-chlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (1), attempts to improve the NK(2) affinity have resulted in the discovery of N-[(R,R)-(E)-1-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (9, DNK333) exhibiting a 5-fold improved affinity to the NK(2) receptor in comparison to 1. Simplification of the structure via elimination of a chiral centre led to 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-(3,4-dichlorobenzyl)-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamide (22), a potent and fairly balanced NK(1)/NK(2) antagonist.     

9-[(Hydroxymethyl)phenyl]adenines: new aryladenine substrates of adenosine deaminase

New phenyl adenine compounds 5-7 were synthesized as analogues of adenosine and studied for their adenosine deaminase (ADA) substrate activity. The 9-[(o-hydroxymethyl)phenyl]methyl]adenine 5 and 9-[(m-hydroxymethyl)phenyl]adenine 7 were deaminated by ADA, and 9-[(o-hydroxyethyl)phenyl]adenine 6 was not deaminated up to 7 days. The ADA substrates 5 and 7 were deaminated quantitatively to their inosine analogues in 10 and 6h, respectively.     

Design and synthesis of positional isomers of 5 and 6-bromo-1-[(phenyl)sulfonyl]-2-[(4-nitrophenoxy)methyl]-1H-benzimidazoles as possible antimicrobial and antitubercular agents

In this Letter, we report the structure–activity relationship (SAR) studies on series of positional isomers of 5(6)-bromo-1-[(phenyl)sulfonyl]-2-[(4-nitrophenoxy)methyl]-1H-benzimidazoles derivatives 7(a–j) and 8(a–j) synthesized in good yields and characterized by ¹H NMR, ¹³C NMR and mass spectral analyses. The crystal structure of 7a was evidenced by X-ray diffraction study. The newly synthesized compounds were evaluated for their in vitro antibacterial activity against Staphylococcus aureus, (Gram-positive), Escherichia coli and Klebsiella pneumoniae (Gram-negative), antifungal activity against Candida albicans, Aspergillus flavus and Rhizopus sp. and antitubercular activity against Mycobacterium tuberculosis H37Rv, Mycobacterium smegmatis, Mycobacterium fortuitum and MDR-TB strains. The synthesized compounds displayed interesting antimicrobial activity. The compounds 7b, 7e and 7h displayed significant activity against Mycobacterium tuberculosis H37Rv strain.     

Cytotoxicity and Antibacterial Evaluation of O-Alkylated/Acylated Quinazolin-4-one Schiff Bases

A series of quinazolin-4-one Schiff bases were synthesized and tested in vitro for their cytotoxicity against two cancerous cell lines (MCF-7, Caco-2) and a human embryonic cell line (HEK-293) including their antibacterial evaluation against two Gram-positive and four Gram-negative bacterial strains. Most of the quinazoline-Schiff bases exhibited potent cytotoxicity against Caco-2. 3-[(Z)-({4-[(But-2-yn-1-yl)oxy]phenyl}methylidene)amino]-2-methylquinazolin-4(3H)-one ( 6f ) with the O-butyne functional group displayed three-fold higher cytotoxic activity (IC₅₀=376.8 μM) as compared to 5-fluorouracil (5-FU; IC₅₀=1086.1 μM). However, all compounds were found to be toxic to HEK-293, except for 3-[(Z)-({4-[(2,4-difluorophenyl)methoxy]phenyl}methylidene)amino]-2-methylquinazolin-4(3H)-one ( 6h ) that showed ∼three-fold lower toxicity and higher selectivity index than 5-FU. Structure–activity relationship (SAR) analysis revealed that O-alkylation generally increased the anticancer activity and selectivity of quinazoline-4-one Schiff bases toward Caco-2 cells. The fluorinated Schiff-base generally exhibited even more significant cytotoxic activity compared to their chlorine analogs. Surprisingly, none of the quinazoline-4-one Schiff bases displayed encouraging antibacterial activity against the bacterial strains investigated. Most of the compounds were predicted to show compliance with the Lipinski parameters and ADMET profiles, indicating their drug-like properties.