The design and discovery of water soluble 4-substituted-2,6-dimethylfuro[2,3-d]pyrimidines as multitargeted receptor tyrosine kinase inhibitors and microtubule targeting antitumor agents

The design, synthesis and biological evaluations of fourteen 4-substituted 2,6-dimethylfuro[2,3-d]pyrimidines are reported. Four compounds (11–13, 15) inhibit vascular endothelial growth factor receptor-2 (VEGFR-2), platelet-derived growth factor receptor β (PDGFR-β), and target tubulin leading to cytotoxicity. Compound 11 has nanomolar potency, comparable to sunitinib and semaxinib, against tumor cell lines overexpressing VEGFR-2 and PDGFR-β. Further, 11 binds at the colchicine site on tubulin, depolymerizes cellular microtubules and inhibits purified tubulin assembly and overcomes both βIII-tubulin and P-glycoprotein-mediated drug resistance, and initiates mitotic arrest leading to apoptosis. In vivo, its HCl salt, 21, reduced tumor size and vascularity in xenograft and allograft murine models and was superior to docetaxel and sunitinib, without overt toxicity. Thus 21 affords potential combination chemotherapy in a single agent.     

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.     

Structure based drug design and in vitro metabolism study: Discovery of N-(4-methylthiophenyl)-N,2-dimethyl-cyclopenta[d]pyrimidine as a potent microtubule targeting agent

We report a series of tubulin targeting agents, some of which demonstrate potent antiproliferative activities. These analogs were designed to optimize the antiproliferative activity of 1 by varying the heteroatom substituent at the 4′-position, the basicity of the 4-position amino moiety, and conformational restriction. The potential metabolites of the active compounds were also synthesized. Some compounds demonstrated single digit nanomolar IC₅₀ values for antiproliferative effects in MDA-MB-435 melanoma cells. Particularly, the S-methyl analog 3 was more potent than 1 in MDA-MB-435 cells (IC₅₀?=?4.6?nM). Incubation of 3 with human liver microsomes showed that the primary metabolite of the S-methyl moiety of 3 was the methyl sulfinyl group, as in analog 5. This metabolite was equipotent with the lead compound 1 in MDA-MB-435 cells (IC₅₀?=?7.9?nM). Molecular modeling and electrostatic surface area were determined to explain the activities of the analogs. Most of the potent compounds overcome multiple mechanisms of drug resistance and compound 3 emerged as the lead compound for further SAR and preclinical development.     

Alkaloids from the mangrove endophytic fungus Diaporthe phaseolorum SKS019

Six new alkaloids including four new chromeno[3,2-c]pyridines, diaporphasines A-D (1–4), and two new isoindolinones, meyeroguillines C and D (6–7), as well as three known compounds meyeroguilline A (5), 5-deoxybostrycoidin (8), and fusaristatin A (9), were isolated from an endophytic fungus Diaporthe phaseolorum SKS019. Their structures were determined by analysis of 1D and 2D NMR and mass spectroscopic data. Compounds 1–9 are alkaloid components reported for the first time from the Diaporthe sp., and diaporphasines A-D (1–4) are the third examples of alkaloids possessing the unique chromeno[3,2-c]pyridine nucleus. All isolated compounds 1–9 were evaluated for their cytotoxic activity in vitro using MDA-MB-435, HepG2, MCF10A, HCT116, and NCI-H460 human cell lines. Compound 8 exhibited cytotoxicity against MDA-MB-435 and NCI-H460 human cancer cell lines with IC₅₀ values of 5.32 and 6.57 μM, respectively, and compound 9 showed growth-inhibitory activity against MDA-MB-435 human cancer cell line with IC₅₀ value of 8.15 μM.     

Dual EGFR/HER2 inhibitors and apoptosis inducers: New benzo[g]quinazoline derivatives bearing benzenesulfonamide as anticancer and radiosensitizers

Dual targeting of EGFR and HER2 is a proven anticancer strategy for the treatment of solid tumors. An array of new N-substituted-2-(4-oxo-3-(4-sulfamoylphenyl)-3,4-dihydrobenzo[g]quinazolin-2-ylthio) acetamides 5–18 were designed and synthesized from the starting compound 4-(2-mercapto-4-oxobenzo[g]quinazolin-3(4H)-yl) benzenesulfonamide 4. The targeted compounds were screened for their cytotoxic activity against MDA-MB-231 breast cancer cell line. The IC₅₀ of all the compounds were in the range of 0.36–40.90 µM. The percentage inhibition towards EGFR was measured and found to be in the range of 63.00–16.90 %. The most potent compounds 5, 9, 15, 17 and 18 were further screened for their activity against both EGFR and HER2 receptors. The compounds showed IC₅₀ in the range of 0.64–1.81 µM for EGFR and 1.13–2.21 µM for HER2, in comparison to erlotinib, the reference drug. Compound 17, the most potent towards EGFR in this series, undergoes cell cycle analysis and was found to arrest the cycle at the G2/M phase. Measurement of the cytotoxicity of compound 17 against normal breast cell line showed mild cytotoxic activity. The most potent compounds were subjected to a single dose of 8 Gy of γ-radiation and the cytotoxicity of the tested compounds was found to increase after irradiation, thus proving the synergistic effect of γ-irradiation. Molecular docking was adopted for all the synthesized compounds to confirm their mechanism of action.     

Design,synthesis and biological evaluation of new carbazole derivatives as anti-cancer and anti-migratory agents

Based on the efficacy of EHop-016 as an inhibitor of migration and Rac1 activation, a new series of carbazole derivatives has been synthesized. Cytotoxic and anti-migratory effects of these compounds were evaluated in MCF-7 and MDA-MB-231 breast cancer cell lines. Preliminary investigations of their anticancer activity demonstrated that several compounds have moderate antiproliferative effects on cancer cell lines with GI₅₀ values in the range of 13–50?µM. Furthermore, compounds 3b and 11b inhibit migration activity of metastatic cell line MDA-MB-231 by 32% and 34%, respectively. Compound 11b was shown to inhibit activation of the Rho GTPase Rac1 by 55% at 250?nM in both MDA-MB-231 and MDA-MB-435 cell lines. Compared with the IC₅₀ of Rac1 inhibition by lead compound EHop-016 of 1.1?µM, compound 11b demonstrates 4X improved in vitro efficacy.     

Phytochemical and chemotaxonomic study on Pholidota pallida lindl

Phytochemical investigation of Pholidota pallida Lindl. led to the isolation of eleven compounds 1–11 (coelonin 1, lusianthridin 2, flavanthrin 3, batatasin-Ⅲ 4, 3′,5-dihydroxy-2-(4-hydroxybenzyl)-3-methoxybibenzyl 5, gigantol 6, 3-[2-(3-hydroxyphenyl) ethyl]-2,4-bis[(4-hydroxyphenyl) methyl]-5-methoxyphenol 7, hydroxytyrosyl butyrate 8, (24R)-ethylcholest-5-en-3-ol-7-one 9, taraxerone 10, friedelin 11) including three phenanthrenes 1–3, four bibenzyls 4–7, one hydroxytyrosyl 8, one steroid 9 and two terpenoids 10–11. The structures of these compounds were elucidated by spectroscopic analyses. This is the first report of isolation of compounds 1–11 from Pholidota pallida and compounds 5 and 8–11 within genus Pholidota. Compound 8 is a new natural product, isolated from a natural source for the first time. Furthermore, the chemotaxonomic significance of the isolates was also discussed.     

Novel N-substituted 5-aminosalicylamides as dual inhibitors of cyclooxygenase and 5-lipoxygenase enzymes: Synthesis,biological evaluation and docking study

Three new series of 5-aminosalicylic acid derivatives; series I (14, 16–18), series II (19–30) and series III (31–41) were synthesized as potential dual COX-2/5-LOX inhibitors. Their chemical structures were confirmed using spectroscopic tools including IR, ¹H NMR, ¹³C NMR, mass spectroscopy and elemental analyses. The anti-inflammatory activity for all target compounds was evaluated in vivo using carrageenan-induced paw edema. Compound 36 showed the highest anti-inflammatory activity (114.12%) relative to reference drug indomethacin at 4 h interval. Selected derivatives were evaluated in vitro to inhibit ovine COX-1, human recombinant COX-2 and 5-LOX enzymes. Compounds 34 & 35 exhibited significant COX-2 inhibition (IC₅₀ = 0.10 µM) with significant COX-2 selectivity indices (SI = 135 & 145 respectively) approximate to celecoxib (IC₅₀ = 0.049 µM, SI = 308.16) and exceeding indomethacin (IC₅₀ = 0.51 µM, SI = 0.08). Interestingly, all compounds showed superior 5-LOX inhibitory activity about 2–5 times relative to zileuton. Compound 16 was the superlative 5-LOX inhibitor that revealed (IC₅₀ = 3.41 µM) relative to zileuton (IC₅₀ = 15.6 µM). Compounds 34, 35, 36 and 41 showed significant dual COX-2/5-LOX inhibitions. The gastric ulcerogenic effect of compound 36 was examined on gastric mucosa of albino rats and they showed superior GI safety profile compared with indomethacin. Molecular docking studies of the compounds into the binding sites of COX-1, COX-2 and 5-LOX allowed us to shed light on the binding mode of these novels dual COX and 5-LOX inhibitors.     

Synthesis and evaluation of 7-chloro-4-(piperazin-1-yl)quinoline-sulfonamide as hybrid antiprotozoal agents

A new series of 4-aminochloroquinoline based sulfonamides were synthesized and evaluated for antiamoebic and antimalarial activities. Out of the eleven compounds evaluated (F1–F11), two of them (F3 and F10) showed good activity against Entamoeba histolytica (IC₅₀ <5 μM). Three of the compounds (F5, F7 and F8) also displayed antimalarial activity against the chloroquine-resistant (FCR-3) strain of Plasmodium falciparum with IC₅₀ values of 2 μM. Compound F7, whose crystal structure was also determined, inhibited β-haematin formation more potently than quinine. To further understand the action of hybrid molecules F7 and F8, molecular docking was carried out against the homology model of P. falciparum enzyme dihydropteroate synthase (PfDHPS). The complexes showed that the inhibitors place themselves nicely into the active site of the enzyme and exhibit interaction energy which is in accordance with our activity profile data. Application of Lipinski ‘rule of five’ on all the compounds (F1–F11) suggested high drug likeness of F7 and F8, similar to quinine.     

One new α-pyrone and one new fatty acid derivative from mangrove-derived fungus Phomopsis sp. HYP11

One new α-pyrone derivative (S)-3-(4-methoxy-3-methyl-2-oxo-2H-pyran-6-yl)butyl acetate (1) and one new fatty acid derivative (4S,5S)-5-acetoxy-4-hydroxyhexanoic acid (2), along with six known compounds (3–8) were obtained from the mangrove-derived fungus Phomopsis sp. HYP11. Their structures and absolute configurations were determined by detailed 1D and ²D NMR, HR-ESI-MS spectral, and quantum chemical electronic circular dichroism (ECD) calculations. Compounds 2, 3, 5, 6 and 8 showed antioxidant activity with the IC₅₀ values range of 0.09–0.67 mM, especially compounds 5 and 6 showed stronger antioxidant activity than the positive control trolox (IC₅₀ = 0.29 mM). Compound 8 showed weak antagonistic effect on Ralstonia solanacearum with the MIC value of 50 μg/mL.     

Design,synthesis and preclinical evaluation of 5-methyl-N4-aryl-furo[2,3-d]pyrimidines as single agents with combination chemotherapy potential

The design, synthesis and biological evaluation of 4-substituted 5-methyl-furo[2,3-d]pyrimidines is described. The Ullmann coupling of 5-methyl-furo[2,3-d]pyrimidine with aryl iodides was successfully optimized to synthesize these analogs. Compounds 6–10 showed single-digit nanomolar inhibition of EGFR kinase. Compounds 1 and 6–10 inhibited VEGFR-2 kinase better than or equal to sunitinib. Compounds 1 and 3–10 were more potent inhibitors of PDGFR-β kinase than sunitinib. In addition, compounds 4–11 had higher potency in the CAM angiogenesis assay than sunitinib. Compound 1 showed in vivo efficacy in an A498 renal xenograft model in mice. Multiple RTK and tubulin inhibitory attributes of 1, 4, 6 and 8 indicates that these compounds may be valuable preclinical single agents targeting multiple intracellular targets.     

Synthesis of N4-(substituted phenyl)-N4-alkyl/desalkyl-9H-pyrimido[4,5-b]indole-2,4-diamines and identification of new microtubule disrupting compounds that are effective against multidrug resistant cells

A series of fourteen N⁴-(substituted phenyl)-N⁴-alkyl/desalkyl-9H-pyrimido[4,5-b]indole-2,4-diamines was synthesized as potential microtubule targeting agents. The synthesis involved a Fisher indole cyclization of 2-amino-6-hydrazinylpyrimidin-4(3H)-one with cyclohexanone, followed by oxidation, chlorination and displacement with appropriate anilines. Compounds 6, 14 and 15 had low nanomolar potency against MDA-MB-435 tumor cells and depolymerized microtubules. Compound 6 additionally had nanomolar GI₅₀ values against 57 of the NCI 60-tumor panel cell lines. Mechanistic studies showed that 6 inhibited tubulin polymerization and [³H]colchicine binding to tubulin. The most potent compounds were all effective in cells expressing P-glycoprotein or the βIII isotype of tubulin, which have been associated with clinical drug resistance. Modeling studies provided the potential interactions of 6, 14 and 15 within the colchicine site.     

Facile synthesis of carbon-11-labeled sEH/PDE4 dual inhibitors as new potential PET agents for imaging of sEH/PDE4 enzymes in neuroinflammation

To develop PET tracers for imaging of neuroinflammation, new carbon-11-labeled sEH/PDE4 dual inhibitors have been synthesized. The reference standard N-(4-methoxy-2-(trifluoromethyl)benzyl)benzamide (1) and its corresponding desmethylated precursor N-(4-hydroxy-2-(trifluoromethyl)benzyl)benzamide (2) were synthesized from (4-methoxy-2-(trifluoromethyl)phenyl)methanamine and benzoic acid in one and two steps with 84% and 49% overall chemical yield, respectively. The standard N-(4-methoxy-2-(trifluoromethyl)benzyl)-1-propionylpiperidine-4-carboxamide (MPPA, 4) and its precursor N-(4-hydroxy-2-(trifluoromethyl)benzyl)-1-propionylpiperidine-4-carboxamide (5) were synthesized from methyl 4-piperidinecarboxylate, propionyl chloride and (4-methoxy-2-(trifluoromethyl)phenyl)methanamine in two and three steps with 62% and 34% overall chemical yield, respectively. The target tracers N-(4-[¹¹C]methoxy-2-(trifluoromethyl)benzyl)benzamide ([¹¹C]1) and N-(4-[¹¹C]methoxy-2-(trifluoromethyl)benzyl)-1-propionylpiperidine-4-carboxamide ([¹¹C]MPPA, [¹¹C]4) were prepared from their corresponding precursors 2 and 5 with [¹¹C]CH₃OTf through O-[¹¹C]methylation and isolated by HPLC combined with SPE in 25–35% radiochemical yield, based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the molar activity (A_M) at EOB was 370–740 GBq/μmol with a total synthesis time of 35–40-minutes from EOB.     

Bioactive polyhydroxylated steroids from the Hainan soft coral Sinularia depressa Tixier-Durivault

Two new steroids, (2β,3β,4α,5α,8β)-4-methylergost-24(28)-ene-2,3,8-triol (1) and (3β,7α)-24-methyl-7-hydroperoxycholest-5,24(28)-diene-3-ol (2), together with 13 known analogues (3–15) were isolated from the soft coral Sinularia depressa Tixier-Durivault. The structures of the new compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. In the bioassay in vitro, compounds 3a, 4, and 14 exhibited potent PTP1B inhibitory activity, being similar as that of positive control oleanolic acid. Compound 14 also displayed a notable neuroprotective activity against both amyloid-β_25–35- and serum deprivation-induced injuries in SH-SY5Y cells while compound 11 showed a considerable antibacterial activity against Staphylococcus aureus. Preliminary structure–activity relationships of these steroids were discussed.     

Adamantane amine-linked chloroquinoline derivatives as chloroquine resistance modulating agents in Plasmodium falciparum

Previously we have shown that pentacycloundecylamine-chloroquinoline (PCU-CQ) conjugates possess significant chemosensitizing abilities and can circumvent the resistance associated with chloroquine (CQ) resistant plasmodia. In order to further explore structurally related polycyclic compounds as reversed CQ agents we synthesized a series of eight aza-adamantanol (1–4) and adamantane-imine (5–8) CQ conjugates. All conjugates showed limited cytotoxicity against CHO cells (IC₅₀?>?37?µM). Compounds 1, 2 and 5 were highly active (K1 IC₅₀?<?100?nM) exhibiting a 3–4-fold increase in antiplasmodial activity against CQ resistant strain K1 compared to CQ. Reduced cross-resistance (resistance index, RI: 2–4.3) relative to CQ (RI?=?38) was also observed for these compounds. Compound 1 which showed an 18-fold enhancement at retaining its activity against the K1 strain compared to CQ is a promising candidate to substitute CQ in P. falciparum resistant malaria.     

Synthesis of novel pyrrole and pyrrolo[2,3-d]pyrimidine derivatives bearing sulfonamide moiety for evaluation as anticancer and radiosensitizing agents

Pyrroles and pyrrolo[2,3-d]pyrimidines were reported to act as potent anticancer agents, in this work, a series of novel 2-substituted-3-cyano-4-phenyl-pyrrole 5, 6, 11–18, and 5-phenyl-pyrrolo[2,3-d]pyrimidine derivatives 7–10, 19–24 bearing either sulfathiazole or sulfapyridine were synthesized. The structures of these compounds were confirmed by elemental analysis, IR, ¹H NMR and mass spectral data. All the newly synthesized compounds were evaluated for their in vitro cytotoxicity against liver and breast cancer cell line (HEPG2 and MCF7). Most of the screened compounds showed interesting cytotoxic activities compared with the used reference drug (doxorubicin). The radiosensitizing ability of some of the synthesized compounds was studied and the results showed an increase in the cell killing effect of γ-radiation after combination with the tested compounds.     

Chemical constituents from the seeds of Raphanus sativus L. and their chemotaxonomic significance

The phytochemical investigations on the seeds of Raphanus sativus L. led to the isolation and identification of 15 compounds, including eleven sinapoyl derivatives (1–11), two terpenes (12–13), and two phenolic acids (14–15). All chemical structures were elucidated via ¹H NMR and ¹³C NMR spectroscopic methods, and further supported by comparison with literature data. Compound 11 was isolated from the genus Raphanus for the first time. Notably, Compounds 7, 9, and 12–14 were reported in the Brassicaceae family for the first time. The chemotaxonomic significance of these compounds is discussed.     

Synthesis and evaluation of (17α,20E)21-[125I]Iodo-11-substituted-19-norpregna-1,3,5(10),20-tetraene-3,17β-diols: the influence of 11-stereochemistry on tissue distribution of radioiodinated estrogens

The 21-tri-n-butylstannyl derivatives of (17α,20E)-11α and β-methoxy-19-norpregna-1,3,5(10),20-tetraene-3,17β-diol were synthesized and characterized. These compounds, as well as the 11-unsubstituted compound were converted via electrophilic ipso radioiododestannylation to the corresponding 21[¹²⁵I]iodo analogs at the no-carrier-added level in 73–90% isolated radiochemical yields. The radiochemical 4c [IVαME₂, (17,20E)-21[¹²⁵I]iodo-11α-methoxy-19-norpregna-1,3,5(10) ,20-tetraene-3,17β-diol] was evaluated in immature female rats and the results compared to those previously reported for 4a (IVE₂) and 4b (IVβ ME₂) to determine the influence of 11-substitution on the ability of the compounds to function as estrogen receptor-seeking agents in vivo. The results indicated that the uptake of 11α-methoxy derivative in the target organ was substantially lower, of shorter duration, with a much smaller specific receptor binding component than the other two radioligands. The distribution profile of the three 17α-iodovinyl estrogens paralleled that previously reported for the corresponding 17α-ethynyl estrogens and this study suggests that the in vivo pharmacological results reported for the 17α-ethynyl estrogens may be used to predict the in vivo behavior of the corresponding 17α-iodovinyl analogs.     

3-Aryl/Heteroaryl-5-amino-1-(3′,4′,5′-trimethoxybenzoyl)-1,2,4-triazoles as antimicrotubule agents. Design,synthesis, antiproliferative activity and inhibition of tubulin polymerization

Many natural and synthetic substances are known to interfere with the dynamic assembly of tubulin, preventing the formation of microtubules. In our search for potent and selective antitumor agents, a novel series of 1-(3′,4′,5′-trimethoxybenzoyl)-5-amino-1,2,4-triazoles were synthesized. The compounds had different heterocycles, including thiophene, furan or the three isomeric pyridines, and they possessed a phenyl ring bearing electron-releasing or electron-withdrawing substituents at the 3-position of the 5-amino-1,2,4-triazole system. Most of the twenty-two tested compounds showed moderate to potent antiproliferative activities against a panel of solid tumor and leukemic cell lines, with four (5j, 5k, 5o and 5p) showing strong antiproliferative activity (IC₅₀ < 1 μM) against selected cancer cells. Among them, several molecules preferentially inhibited the proliferation of leukemic cell lines, showing IC₅₀ values 2-100-fold lower for Jurkat and RS4;11 cells than those for the three lines derived from solid tumors (HeLa, HT-29 and MCF-7 cells). Compound 5k strongly inhibited tubulin assembly, with an IC₅₀ value of 0.66 μM, half that obtained in simultaneous experiments with CA-4 (IC₅₀ = 1.3 μM).