Design,synthesis and structure–activity relationship of 2-(3′,4′,5′-trimethoxybenzoyl)-benzo[b]furan derivatives as a novel class of inhibitors of tubulin polymerization

The biological importance of microtubules in mitosis and cell division makes them an interesting target for the development of anticancer agents. Small molecules such as benzo[b]furans are attractive as inhibitors of tubulin polymerization. Thus, a new class of inhibitors of tubulin polymerization based on the 2-(3′,4′,5′-trimethoxybenzoyl)-benzo[b]furan molecular skeleton, with electron-donating (Me, OMe or OH) or electron-withdrawing (F, Cl and Br) substituents on the benzene ring, was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization and cell cycle effects. Adding a methyl group at the C-3 position resulted in increased activity. The most promising compound in this series was 2-(3′,4′,5′-trimethoxybenzoyl)-3-methyl-6-ethoxy-benzo[b]furan, which inhibits cancer cell growth at nanomolar concentrations and interacts strongly with tubulin by binding to the colchicine site.     

Substituted 2-(3′,4′,5′-trimethoxybenzoyl)-benzo[b]thiophene derivatives as potent tubulin polymerization inhibitors

The central role of microtubules in cell division and mitosis makes them a particularly important target for anticancer agents. On our early publication, we found that a series of 2-(3′,4′,5′-trimethoxybenzoyl)-3-aminobenzo[b]thiophenes exhibited strong antiproliferative activity in the submicromolar range and significantly arrested cells in the G2–M phase of the cell cycle and induced apoptosis.In order to investigate the importance of the amino group at the 3-position of the benzo[b]thiophene skeleton, the corresponding 3-unsubstituted and methyl derivatives were prepared. A novel series of inhibitors of tubulin polymerization, based on the 2-(3,4,5-trimethoxybenzoyl)-benzo[b]thiophene molecular skeleton with a methoxy substituent at the C-4, C-5, C-6 or C-7 position on the benzene ring, was evaluated for antiproliferative activity against a panel of five cancer cell lines, for inhibition of tubulin polymerization and for cell cycle effects. Replacing the methyl group at the C-3 position resulted in increased activity compared with the corresponding 3-unsubstituted counterpart. The structure–activity relationship established that the best activities were obtained with the methoxy group placed at the C-4, C-6 or C-7 position. Most of these compounds exhibited good growth inhibition activity and arrest K562 cells in the G2–M phase via microtubule depolymerization.     

Design and modeling of new platelet-activating factor antagonists. 2. Synthesis and biological activity of 1,4-bis-(3′,4′,5′-trimethoxybenzoyl)-2-alkyl and 2-alkyloxymethylpiperazines

In the continuation of our investigations on the structure of platelet-activating factor (PAF)-receptor, 25 additional 2-substituted 1,4-bis-(poly- and mono methoxybenzoyl)-piperazines were synthesized and their in vitro biological activities measured. Substituent at position 2 is representative of the classical balance lipophilicity/hydrophilicity, i.e. alkyl, phenylalkyl, alkoxy and polyalkoxy groups. A potent PAF-induced platelet aggregation inhibitory activity measured in PRP medium is obtained with 5c, IC₅₀ = 6 × 10⁻⁸ M, which displaces the [³H]PAF from platelet membrane with an EC₅₀ = 6 × 10⁻⁸ M, and compound 4 presents an EC₅₀ of 3 × 10⁻⁸ M. Examination of structure-activity relationships shows that molecules bearing a hydrophilic or slightly hydrophobic appendix in position-2 are still potent; their IC₅₀ being included between 10⁻⁶ and 10⁻⁷ M. After quantitative analysis, it seems that in PRP medium, the role of serum albumin must be taken into account instead of a pure hydrophobic interaction of the appendix Z into the receptor. The role of the methoxy groups in producing a potent antagonistic activity is demonstrated by syntheses of several 2-octylpiperazine analogs. These specific features will be quatitatively analysed in the following related publication (part 3).     

Symmetrical α-bromoacryloylamido diaryldienone derivatives as a novel series of antiproliferative agents. Design,synthesis and biological evaluation

In a continuing study of hybrid compounds containing the α-bromoacryloyl moiety as potential anticancer drugs, we synthesized a novel series of hybrids 4a–h, in which this moiety was linked to a 1,5-diaryl-1,4-pentadien-3-one system. Many of the conjugates prepared (4b, 4c, 4e and 4g) demonstrated pronounced, submicromolar antiproliferative activity against four cancer cell lines. Moreover, compound 4b induced apoptosis through the mitochondrial pathway and activated caspase-3 in a concentration-dependent manner.     

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 biological evaluation of 2-substituted-4-(3′,4′,5′-trimethoxyphenyl)-5-aryl thiazoles as anticancer agents

Antitumor agents that bind to tubulin and disrupt microtubule dynamics have attracted considerable attention in the last few years. To extend our knowledge of the thiazole ring as a suitable mimic for the cis-olefin present in combretastatin A-4, we fixed the 3,4,5-trimethoxyphenyl at the C4-position of the thiazole core. We found that the substituents at the C2- and C5-positions had a profound effect on antiproliferative activity. Comparing compounds with the same substituents at the C5-position of the thiazole ring, the moiety at the C2-position influenced antiproliferative activities, with the order of potency being NHCH₃ > Me ? N(CH₃)₂. The N-methylamino substituent significantly improved antiproliferative activity on MCF-7 cells with respect to C2-amino counterparts. Increasing steric bulk at the C2-position from N-methylamino to N,N-dimethylamino caused a 1–2 log decrease in activity. The 2-N-methylamino thiazole derivatives 3b, 3d and 3e were the most active compounds as antiproliferative agents, with IC₅₀ values from low micromolar to single digit nanomolar, and, in addition, they are also active on multidrug-resistant cell lines over-expressing P-glycoprotein. Antiproliferative activity was probably caused by the compounds binding to the colchicines site of tubulin polymerization and disrupting microtubule dynamics. Moreover, the most active compound 3e induced apoptosis through the activation of caspase-2, -3 and -8, but 3e did not cause mitochondrial depolarization.     

Design,synthesis, and anticancer activity of C8-substituted-4′-thionucleosides as potential HSP90 inhibitors

A series of C8-substituted-4′-thioadenosine analogs 3a–3g, 15, and 17 and their truncated derivatives 4a–4j, 23–25, and 27 have been successfully synthesized from d-ribose and d-mannose, respectively, employing Pummerer type or Vorbrüggen condensation reactions and the functionalization at the C8-position of nucleobase via Stille coupling or nucleophilic aromatic substitution reactions as key steps. All the synthesized compounds were assayed for their HSP90 inhibitory activity, but they were found to be inactive up to 100 μM. However, the 8-iodo derivatives 15, 17, and 27 exhibited potent anticancer activity, indicating that different mechanism of action might be involved in their biological activity.     

Design,synthesis, and biological activity of 5′-phenyl-1,2,5,6-tetrahydro-3,3′-bipyridine analogues as potential antagonists of nicotinic acetylcholine receptors

Starting from a known non-specific agonist (1) of nicotinic acetylcholine receptors (nAChRs), rationally guided structural-based design resulted in the discovery of a small series of 5′-phenyl-1,2,5,6-tetrahydro-3,3′-bipyridines (3a–3e) incorporating a phenyl ring off the pyridine core of 1. The compounds were synthesized via successive Suzuki couplings on a suitably functionalized pyridine starting monomer 4 to append phenyl and pyridyl substituents off the 3- and 5-positions, respectively, and then subsequent modifications were made on the flanking pyridyl ring to provide target compounds. Compound 3a is a novel antagonist, which is highly selective for α3β4 nAChR (K_i = 123 nM) over the α4β2 and α7 receptors.     

Synthesis and anti-HCV activity of 3′,4′-oxetane nucleosides

Hepatitis C virus afflicts approximately 180 million people worldwide and currently there are no direct acting antiviral agents available to treat this disease. Our first generation nucleoside HCV inhibitor, RG7128 has already established proof-of-concept in the clinic and is currently in phase IIb clinical trials. As part of our continuing efforts to discover novel anti-HCV agents, 3′,4′-oxetane cytidine and adenosine nucleosides were prepared as inhibitors of HCV RNA replication. These nucleosides were shown not to be inhibitors of HCV as determined in a whole cell subgenomic replicon assay. However, 2′-mono/diflouro analogs, 4, 5, and 6 were readily phosphorylated to their monophosphate metabolites by deoxycytidine kinase and their triphosphate derivatives were shown to be inhibitors of HCV NS5B polymerase in vitro. Lack of anti-HCV activity in the replicon assay may be due to the inability of the monophosphates to be converted to their corresponding diphosphates.     

Design,synthesis and molecular docking of α,β-unsaturated cyclohexanone analogous of curcumin as potent EGFR inhibitors with antiproliferative activity

A type of novel α,β-unsaturated cyclohexanone analogous, which designed based on the curcumin core structure, have been discovered as potential EGFR inhibitors. These compounds exhibit potent antiproliferative activity in two human tumor cell lines (Hep G2 and B16-F10). Among them, compounds I₃ and I₁₂ displayed the most potent EGFR inhibitory activity (IC₅₀ = 0.43 μM and 1.54 μM, respectively). Molecular docking of I₁₂ into EGFR TK active site was also performed. This inhibitor nicely fitting the active site might well explain its excellent inhibitory activity.     

Design,synthesis and evaluation of 4′-OH-flurbiprofen-chalcone hybrids as potential multifunctional agents for Alzheimer’s disease treatment

A series of 4′-OH-flurbiprofen-chalcone hybrids were designed, synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer’s disease. The biological screening results indicated that most of these hybrids exhibited good multifunctional activities. Among them, compounds 7k and 7m demonstrated the best inhibitory effects on self-induced Aβ_1–42 aggregation (60.0% and 78.2%, respectively) and Cu²⁺-induced Aβ_1–42 aggregation (52.4% and 95.0%, respectively). Moreover, these two representative compounds also exhibited good antioxidant activities, MAO inhibitions, biometal chelating abilities and anti-neuroinflammatory activities in vitro. Furthermore, compound 7m displayed appropriate blood-brain barrier permeability. These multifunctional properties highlight compound 7k and 7m as promising candidates for further development of multi-functional drugs against AD.     

Natural product-based design,synthesis and biological evaluation of 2′,3,4,4′-tetrahydrochalcone analogues as antivitiligo agents

A bioactive component, 2′,3,4,4′-tetrahydrochalcone (RY3-a) was first isolated from Vernohia anthelmintica (L.) willd seeds, and a set of its analogs, RY3-a-1–RY3-a-15 and RY3-c were designed and synthesized. Biological activity assays showed that RY3-c exhibited better melanogenesis and antioxidant activity and lower toxicity in comparison with RY3-a and butin. Further study tests showed that RY3-c exhibited better melanogenesis activity compared with the positive control 8-methoxypsoralan (8-MOP) in a vitiligo mouse model, suggesting that RY3-c is a good candidate antivitiligo agent. Mechanistic studies showed that RY3-c could repair cell damage induced by excessive oxidative stress and may exert melanin synthesis activity in the mouse melanoma B16F10 cell line by activating the mitogen-activated protein kinase (MAPK) pathway and the upregulation of c-kit.     

3′-3′,3′-5′ and 5′-5′ TpT-Amides: Synthesis,Characterization and Alkaline Hydrolysis

Abstract

A simple procedure is described for the preparation of the title compounds 1, 8 and 9. 3′-3′ or 3′-5′ or 5′-5′ TpT was reacted with a twofold molar excess of TPS in anhydrous DMF, at room temperature, for 5 min, followed by a 1 min in situ treatment of the reaction mixture with excess 7.0 N NH₄OH, at 0°C. The alkaline hydrolysis of 1, 8 and 9 proceeds without the assistance of 3′- and 5′-hydroxyl groups resulting in equimolar mixtures of thymidine (4) and thymidine 3′-phosphoramidate (6) (for the 3′-3′ isomer) or thymidine 5′-phosphoramidate (7) (for the 5′-5′ isomer) or 6 and 7 in equal quantities (for the 3′-5′ isomer).     

Hydrogenolysis of benzylidene acetals: synthesis of benzyl 2,3,6,2′,3′,4′-hexa-O-benzyl-β-cellobioside, -maltoside,and -lactoside,benzyl 2,3,4,2′,3′,4′-hexa-O-benzyl-β-allolactiside,and benzyl 2,3,6,2′,3′,6′-hexa-O-benzyl-β-lactoside

Hydrogenolysis of benzyl penta-O-benzyl-4′,6′-O-benzylidene-β-cellobioside (4), -maltoside (5), and -allolactoside (16) with LiAlH₄-AlCl₃ gave only the corresponding derivatives having HO-6′ free, in yields of 55, 78, and 90%, respectively. The main product of the hydrogenolysis of benzyl penta-O-benzyl-4′,6′-O-benzylidene-β-lactoside (6) also had HO-6′ free, but the isomer having HO-4′ free was also isolated. The role of the C-1 substituent in the galactose moiety in the direction of benzylidene ring-cleavage is discussed.     

Design,synthesis and structure–activity relationship of rhenium 2-arylbenzothiazoles as β-amyloid plaque binding agents

To continue our efforts toward the development of ^99mTc PiB analogs, we have synthesized 24 neutral and lipophilic Re (as a surrogate of ^99mTc) 2-arylbenzothiazoles, and explored their structure–activity relationship for binding to Aβ_1–40 fibrils. These Re complexes were designed and synthesized via the integrated approach, so their ^99mTc analogs would have a greater chance of crossing the blood–brain barrier. While the lipophilicities (log P_C18 = 1.59–3.53) of these Re 2-arylbenzothiazoles were all within suitable range, their binding affinities (K_i = 30–617 nM) to Aβ_1–40 fibrils varied widely depending on the selection and integration of the tetradentate chelator into the 2-phenylbenzothiazole pharmacophore. For potential clinical applications, further refinement to obtain Re 2-arylbenzothiazoles with better binding affinities (<10 nM) will likely be needed. The integrated approach reported here to generate compact, neutral and lipophilic Re 2-arylbenzothiazoles could be applied to other potent pharmacophores as well to convert other current Aβ PET tracers to their ^99mTc analogs for more widespread application via the use of SPECT scanners.     

Facile synthesis of 2′,5′-dideoxy-, 2′,3′-dideoxy- and 3′-deoxy-1,N 6-ethenoadenosine nucleosides

Facile synthetic methods of 2′,5′-dideoxy-, 2′,3′-dideoxy- and 3′-deoxy-1,N ⁶-ethenoadenosine nucleosides by either an enzymatic dideoxyribosyl transfer reaction or a simple chemical reaction were proposed. The synthetic products were isolated and purified by preparative HPLC and their structures were confirmed by¹H NMR (500 MHz) and FAB-MS including high resolution mass measurement. These modified nucleoside analogs have not been reported yet. Therefore, these modified nucleoside analogs are of potential value to be studied further for biological activity such as anticancer or antiviral.     

Oligomerizations of deoxyadenosine bis-phosphates and of their 3′-5′, 3′-3′, and 5′-5′ dimers: Effects of a pyrophosphate-linked,poly(t) analog

A pyrophosphate-linked polynucleotide analog based on thymidine 3,5 bis-phosphate (pTp) catalyzes the oligomerization of activated dimers of pdAp in the presence of MgCl₂. Although no catalysis of the oligomerization of the activated monomer (ImpdAplm) was observed in the presence of MgCl₂, there was a significant stimulation of oligomerization by the template in the presence of MnCl₂.