Synthesis, biological activity, and SAR of antimycobacterial 2- and 8-substituted 6-(2-furyl)-9-(p-methoxybenzyl)purines

A number of 6-(2-furyl)-9-(p-methoxybenzyl)purines carrying a variety of substituents in the 2- or 8-position have been synthesized and their ability to inhibit growth of Mycobacterium tuberculosis in vitro has been determined. It is demonstrated that sterical hindrance in the purine 8-position reduces activity and that C-8 should be unsubstituted. In the purine 2-position small, hydrophobic substituents are beneficial. The electronic properties of the 2-substituents appear to have only a minor influence on bioactivity. The compounds studied exhibit low toxicity toward mammalian cells (VERO cells) and are essentially inactive toward Staphylococcus aureus and Escherichia coli. The most active and selective antimycobacterial in the series detected to date is the novel 2-methyl-6-furyl-9-(p-methoxybenzyl)purine with MIC=0.20 microg/mL against M. tuberculosis and IC(50) against VERO cells >62.5 microg/mL. Also the novel 2-fluoro analog and the previously known 2-chloro compound, both with MIC=0.39 microg/mL, are highly interesting drug candidates.     

Design of quinolinedione-based geldanamycin analogues

Quinoline-5,8-dione-based compounds were designed from the structure of the geldanamycin-bound Hsp-90 active site. The active site model predicted that aromatic substituents should be present at the 2-position, to take advantage of a hydrophobic pocket, and amino substituents should be present at the 6- or 7-position. COMPARE analysis revealed that the LC(50) profile of 2-phenyl-6-(2-chloroethylamino)quinoline-5,8-dione has the highest geldanamycin-like activity (0.74 correlation coefficient).     

8-Substituted 2-alkynyl-N9-propargyladenines as A2A adenosine receptor antagonists

Structure–activity relationships of 2-alkynyladenine derivatives were explored by varying substituents at the 9-, 8- and 2-positions of the purine moiety in order to optimize A_2A adenosine receptor antagonist activity in vitro. A propargyl group at the 9-position was found to be important for A_2A antagonist activity, and the introduction of a halogen, aryl, or heteroaryl at the 8-position further enhanced activity. A series of 8-substituted 2-alkynyl-N⁹-propargyladenine derivatives exhibited potent antagonist activity, with IC₅₀ values in the low nM range. Compound 4a from this series was found to be orally active at a dose of 3 mg/kg in a mouse catalepsy model and a 6-hydroxydopamine-lesioned rat model of Parkinson’s disease.     

Synthesis and Herbicidal Activity of Phenoxypropionic Acid Derivatives with Imidazo[1,2-α]pyridine Moiety

Phenoxypropionic acid derivatives (Ia-s) with an imidazo[1,2-a]pyridine moiety were synthesized and their herbicidal activities were examined. The activities were affected dramatically by the substituents on the imidazo[1,2-a]pyridine ring, and good substituents to enhance the herbicidal activity were a cyano group at the 3-position and a chlorine atom at the 6-position. Among the compounds, n-propyl 2-[4-(6-chloro-3-cyano-2-imidazo[1,2-a]pyridinyloxy)phenoxy]propionate(Iq) was most active against gramineous weeds and the activity was comparable to that of the commercial herbicide fluazifop-butyl.     

Structural requirement of chalcones for the inhibitory activity of interleukin-5

Novel chalcones were found as potent inhibitors of interleukin (IL)-5. 1-(2-Benzyloxy-6-hydroxyphenyl)-3-(4-hydroxyphenyl)-2-propen-1-one (2b, 78.8% inhibition at 50microM, IC(50)=25.3microM) was initially identified as a potent inhibitor of IL-5. This shows the compatible activity with budesonide or sophoricoside. To identify structural requirements, 26 chalcones were prepared and their inhibitory activities were tested against IL-5. Among them, compound 4-[(E)-3-(2-cyclohexylmethoxy-6-hydroxyphenyl)-3-oxoprop-1-enyl]benzenesulfonamide (2w, 99.5% inhibition at 50microM, IC(50)=1.8microM) shows the most potent activity. The important structural requirements of these chalcone analogs exhibiting the inhibitory activity against IL-5 were recognized as the following. (1) The hydrophobic group such as benzyloxy or cyclohexylmethoxy at 6-position of A ring is necessary. (2) The existence of phenolic hydroxyl at 6-position of A ring is critical. (3) Propenone unit as alpha,beta-unsaturated ketone is essential. (4) Electron withdrawing groups with hydrogen acceptor property at 4-position of B ring enhance the activity and quantitative structure-activity relationship of 2 regarding these substituents was determined.     

Mutagenicity of quinolines in Salmonella typhimurium TA100. A QSAR study based on hydrophobicity and molecular orbital determinants.

The mutagenicity of 33 quinolines in the Salmonella test using TA98 and TA100 cells has been reported. Significant activity was found only with TA100 cells. Quantitative structure-activity relationships (QSAR) could be formulated using molecular orbital parameters or Hammett constants and hydrophobic parameters for those compounds with substituents in the 6, 7 and 8 positions. The QSAR points to the 2-position on the quinoline ring as being the site for activation by S9 oxidation.     

cis-Nitromethylene neonicotinoids as new nicotinic family: synthesis, structural diversity, and insecticidal evaluation of hexahydroimidazo[1,2-alpha]pyridine

A series of neonicotinoids analogues of hexahydroimidazo[1,2-alpha]pyridine were modified at 5-, 6-, and 7-positions, and their insecticidal activities were evaluated. Introducing a methyl or ethyl at 7-position increased the insecticidal activities, while other substituents decreased activities. When alkyl substituents were introduced to 7-position, the insecticidal activities against Pea aphids decreased in the order methyl (7a)>ethyl (7b)>n-butyl (7e)>phenyl (7f)>n-propyl (7c)>iso-propyl (7d), p-NO(2)-phenyl (7g). Modifications at 5-, 6- or both at 6- and 7-positions with methyl or ethyl were unfavorable to activities. Interestingly, introducing methyl to 7-position not only increased insecticidal activities against pea aphids, but also show higher insecticidal activities than imidacloprid against imidacloprid-resistant brown planthopper.     

Diaza- and triazachrysenes: potent topoisomerase-targeting agents with exceptional antitumor activity against the human tumor xenograft,MDA-MB-435

Several 5,12-diazachrysen-6-ones and 5,6,11-triazachrysen-12-ones were synthesized with varied substituents at the 5- or 11-position, respectively. Each compound was evaluated for its potential to stabilize the cleavable complex formed with TOP1 and DNA. Two analogues with very potent TOP1-targeting activity, 3a and 4a, exhibited cytotoxic activity with IC(50) values at or below 2nM against RPMI8402. Compound 3a was active in vivo by either ip or po administration in the human tumor xenograft athymic nude mice model.     

Pyridazine based inhibitors of p38 MAPK

Trisubstituted pyridazines were synthesized and evaluated as in vitro inhibitors of p38MAPK. The most active isomers were those possessing an aryl group alpha and a heteroaryl group beta relative to the nitrogen atom in the 2-position of the central pyridazine. Additionally, substitution in the 6-position of the central pyridazine with a variety of dialkylamino substituents afforded a set of inhibitors having good (p38 IC50 1-20 nM) in vitro activity.     

Substituted benzylamino-6-(trifluoromethyl)pyrimidin-4(1H)-ones: a novel class of selective human A-FABP inhibitors

The synthesis and biological evaluation of novel human A-FABP inhibitors based on the 6-(trifluoromethyl)pyrimidine-4(1H)-one scaffold is described. Two series of compounds, bearing either an amino or carbon substituent in the 2-position of the pyrimidine ring were investigated. Modification of substituents and chain length optimization led to novel compounds with low micromolar activity and good selectivity for human A-FABP.     

in vitro inhibition of the measles virus by novel ring-expanded ('fat') nucleoside analogues containing the imidazo[4,5-e]diazepine ring system

The synthesis and in vitro anti-measles virus (anti-MV) activity of a class of ring-expanded ('fat') nucleoside analogues (1-4) containing the title heterocyclic ring system are reported. The target compounds were synthesized by base-catalyzed condensations of 4,5-dicarboxylic acid esters of the appropriately substituted imidazole-1-ribosides with suitably substituted guanidine derivatives. Compounds were screened for anti-MV activity in African green monkey kidney cells (CV-1), employing ribavirin as the control standard. While the parent compound 1 itself failed to show any significant antiviral activity against MV, its analogues containing hydrophobic substituents at the 2-position (2) or the 6-position (4) showed promising antiviral activity at submicromolar or micromolar concentration levels with no apparent toxicity to the host cell line. Both compounds showed higher anti-MV activity than the control drug ribavirin.     

Synthesis and SAR of cis-1-benzoyl-1,2,3,4-tetrahydroquinoline ligands for control of gene expression in ecdysone responsive systems

A library of 35 cis-1-benzoyl-2-methyl-4-(phenylamino)-1,2,3,4-tetrahydroquinolines was prepared. The compounds bore various substitutuents on the benzoyl ring, at the 4-position of the phenylamino ring and at the 6-position of the tetrahydroquinoline ring. The compounds were assayed for their ability to cause expression of a reporter gene downstream of an ecdysone response element in a mammalian cell line engineered to express the ecdysone receptor from Aedes aegypti. In general, compounds with small lipophilic substituents at the meta and para-positions of the benzoyl ring and hydrogen or fluorine at the 4-position of the phenylamino ring and the 6-position of the tetrahydroquinoline ring were the most potent.     

Synthesis and biological evaluation of 2,8-disubstituted 9-benzyladenines: discovery of 8-mercaptoadenines as potent interferon-inducers

Recently, we have identified 9-benzyl-8-hydroxyadenines bearing an appropriate substituent (a butoxy, propylthio or butylamino group) at the 2-position as potent interferon (IFN)-inducers. Herein we report the design, synthesis, and IFN-inducing activity of 8-substituted 9-benzyladenines possessing such an appropriate substituent at the 2-position. Introduction of the appropriate substituent into the 2-position of the adenine nucleus gave rise to expression of the activity even in 9-benzyladenines bearing no hydroxyl group at the 8-position. An amino group at the 6-position and a hydroxyl or thiol group carrying an acidic proton at the 8-position are required to express excellent IFN-inducing activity. 9-Benzyl-2-butoxy-8-mercaptoadenine (9) indicated the most potent activity with MEC of 0.001 microM.     

Effect of substituents of the benzoquinone ring on electron-transfer activities of ubiquinone derivatives

The effect of substituents on the 1,4-benzoquinone ring of ubiquinone on its electron-transfer activity in the bovine heart mitochondrial succinate-cytochrome c reductase region is studied by using synthetic ubiquinone derivatives that have a decyl (or geranyl) side-chain at the 6-position and various arrangements of methyl, methoxy and hydrogen in the 2, 3 and 5 positions of the benzoquinone ring. The reduction of quinone derivatives by succinate is measured with succinate-ubiquinone reductase and with succinate-cytochrome c reductase. Oxidation of quinol derivatives is measured with ubiquinol-cytochrome c reductase. The electron-transfer efficacy of quinone derivatives is compared to that of 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone. When quinone derivatives are used as the electron acceptor for succinate-ubiquinone reductase, the methyl group at the 5-position is less important than are the methoxy groups at the 2- and 3-positions. Replacing the 5-methyl group with hydrogen causes a slight increase in activity. However, replacing one or both of 2- and 3-methoxy groups with a methyl completely abolishes electron-acceptor activity. Replacing the 3-methoxy group with hydrogen results in a complete loss of electron-acceptor activity, while replacing the 2-methoxy with hydrogen results in an activity decrease by 70%, suggesting that the methoxy group at the 3-position is more specific than that at the 2-position. The structural requirements for quinol derivatives to be oxidized by ubiquinol-cytochrome c reductase are less strict. All 1,4-benzoquinol derivatives examined show partial activity when used as electron donors for ubiquinol-cytochrome c reductase. Derivatives that possess one unsubstituted position at 2, 3 or 5, with a decyl group at the 6-position, show substrate inhibition at high concentrations. Such substrate inhibition is not observed when fully substituted derivatives are used. The structural requirements for quinone derivatives to be reduced by succinate-cytochrome c reductase are less specific than those for succinate-ubiquinone reductase. Replacing one or both of the 2- and 3-methoxy groups with a methyl and keeping the 5-position unsubstituted (plastoquinone derivatives) yields derivatives with no acceptor activity for succinate-Q reductase. However, these derivatives are reducible by succinate in the presence of succinate-cytochrome c reductase. This reduction is antimycin-sensitive and requires endogenous ubiquinone, suggesting that these (plastoquinone) derivatives can only accept electrons from the ubisemiquinone radical at the Qi site of ubiquinol-cytochrome c reductase, and cannot accept electrons from the QPs of succinate-ubiquinone reductase.     

Uncoupling activities of chalcones and dihydrochalcones on isolated mitochondria from potato tubers and mung bean hypocotyls

The uncoupling properties of 23 chalcones and dihydrochalcones were studied. Twelve compounds completely uncouple oxidative phosphorylation in mung bean hypocotyl and potato tuber mitochondria, four are weak uncouplers and seven are without effect. Usually, mung bean mitochondria are more sensitive to uncoupling agents than potato mitochondria. The uncoupling activity of chalcones and dihydrochalcones appears to be connected with the presence of hydrogen or hydroxyl groups in the 2′-position and hydrogen, hydroxyl or nitrate groups in the 4′-position. The α-β-unsaturated carbonyl system is not essential for activity. For the compounds which are not very lipophilic, substituents on the B-ring are without effect on the uncoupling properties. Phloretin appears to be an active uncoupler; its 6′-glucoside is without effect.     

Design,synthesis, in vitro antiproliferative activity and apoptosis-inducing studies of 1-(3′,4′,5′-trimethoxyphenyl)-3-(2′-alkoxycarbonylindolyl)-2-propen-1-one derivatives obtained by a molecular hybridisation approach

Inhibition of microtubule function using tubulin targeting agents has received growing attention in the last several decades. The indole scaffold has been recognized as an important scaffold in the design of novel compounds acting as antimitotic agents. Indole-based chalcones, in which one of the aryl rings was replaced by an indole, have been explored in the last few years for their anticancer potential in different cancer cell lines. Eighteen novel (3′,4′,5′-trimethoxyphenyl)-indolyl-propenone derivatives with general structure 9 were synthesized and evaluated for their antiproliferative activity against a panel of four different human cancer cell lines. The highest IC₅₀ values were obtained against the human promyelocytic leukemia HL-60 cell line. This series of chalcone derivatives was characterized by the presence of a 2-alkoxycarbonyl indole ring as the second aryl system attached at the carbonyl of the 3-position of the 1-(3′,4′,5′-trimethoxyphenyl)-2-propen-1-one framework. The structure–activity relationship (SAR) of the indole-based chalcone derivatives was investigated by varying the position of the methoxy group, by the introduction of different substituents (hydrogen, methyl, ethyl or benzyl) at the N-1 position and by the activity differences between methoxycarbonyl and ethoxycarbonyl moieties at the 2-position of the indole nucleus. The antiproliferative activity data of the novel synthesized compounds revealed that generally N-substituted indole analogues exhibited considerably reduced potency as compared with their parent N-unsubstituted counterparts, demonstrating that the presence of a hydrogen on the indole nitrogen plays a decisive role in increasing antiproliferative activity. The results also revealed that the position of the methoxy group on the indole ring is a critical determinant of biological activity. Among the synthesized derivatives, compound 9e, containing the 2-methoxycarbonyl-6-methoxy-N-1H-indole moiety exhibited the highest antiproliferative activity, with IC₅₀ values of 0.37, 0.16 and 0.17?μM against HeLa, HT29 and MCF-7 cancer cell lines, respectively, and with considerably lower activity against HL-60 cells (IC₅₀: 18?μM). This derivative also displayed cytotoxic properties (IC₅₀ values ～1?μM) in the human myeloid leukemia U-937 cell line overexpressing human Bcl-2 (U-937/Bcl-2) via cell cycle progression arrest at the G₂-M phase and induction of apoptosis. The results obtained also demonstrated that the antiproliferative activity of this molecule is related to inhibition of tubulin polymerisation. The presence of a methoxy group at the C5- or C6-position of the indole nucleus, as well as the absence of substituents at the N-1-indole position, contributed to the optimal activity of the indole-propenone-3′,4′,5′-trimethoxyphenyl scaffold.     

Synthesis and evaluation of the anti-proliferative activity of diaryl-3-pyrrolin-2-ones and fused analogs

Analogs containing a central 3-pyrrolin-2-one core with different methoxyphenyl and/or indole substituents were prepared and tested for anti-proliferative activity in U-937 cells. The most efficacious analogs were non-rigid, (non-fused) contained methoxyaryl groups located at the 4-position, and contained either methoxyaryl or indole groups located at the 3-position. Both the number of methoxy groups contained in the substituents and the particular location of the indole rings with respect to the lactam carbonyl had significant affects on anti-proliferative activity. This work provides a framework to better understand structure-activity relationships for inducing anti-proliferative activity in diaryl heterocyclic scaffolds.     

Structure-activity Study of Bacteriostatic Kojic Acid Analogs

The bacteriostatic activity of kojic acid derivatives, where various substituents are introduced into the 2- and/or 7-positions was analyzed in terms of the physicochemical characteristics of the substituents using the method developed by Hansch and his co-workers. Analyses show that 1) activity is attributable to the neutral form of the molecule in the medium, 2) the site of action seems to be in a region close to the bacterial cell surface, and 3) the higher the hydrophobicity of the substituents at the 7-position and the greater the electron withdrawal from the 3-hydroxyl group, the stronger the activity.     

Regioselective deacetylation of cellulose acetates by acetyl xylan esterases of different CE-families

Cellulose acetate (CA) was found to be a substrate of several acetyl xylan esterases (AXE). Eight AXE from different carbohydrate esterase (CE) families were tested on their activity against CA with a degree of substitution of 0.7 and 1.4. The classification of the AXEs into CE families according to their structure by hydrophobic cluster analysis followed clearly their activity against CA. Within the same CE family similar, and between the CE families different deacetylation behaviours could be observed. Furthermore, each esterase family showed a distinct regioselective mode of action. The CE 1 family enzymes regioselectively cleaved the substituents in C2- and C3-position, while CE 5 family enzymes only cleaved the acetyl groups in C2-position. CE 4 family enzymes seemed to interact only with the substituents in C3-position. Evidence was found that the deacetylation reaction of the CE 1 family enzymes proceeded faster in C2- than in C3-position of CA. The enzymes were able to cleave acetyl groups from fully substituted anhydroglucose units.