Conformationnally restricted naphthalene derivatives type isocombretastatin A-4 and isoerianin analogues: Synthesis, cytotoxicity and antitubulin activity

β-Glucuronidase-Responsive Albumin-Binding Prodrug of Colchicine-Site Binders for Selective Cancer Therapy

The development of novel therapeutic strategies enabling the selective destruction of tumors while sparing healthy tissues is of great interest to improve the efficacy of cancer chemotherapy. In this context, we designed a β-glucuronidase-responsive albumin-binding prodrug programmed to release a potent Isocombretastatin A-4 analog within the tumor microenvironment. When injected at a non-toxic dose in mice bearing orthotopic triple-negative mammary tumors, this prodrug produced a significant anticancer activity, therefore offering a valuable alternative to the systemic administration of the parent drug.

1,1'-Diarylethylene as a Key Additive for the Visible Light Synthesis of Bioactive Dihydrobenzo[a]phenanthridine Compounds

This study introduces a straightforward synthetic approach for generating 7,8-dihydrobenzo[a]phenanthridine analogs through visible-light-induced cyclization, showing promise as antitumor agents. Unexpectedly, the incorporation of 1,1'-diarylethylene as an additive significantly boosts yield. Through mechanistic investigations, we uncover its crucial role as a trap for the methyl radical formed after the N-O bond cleavage of O-acetyl oxime, promoting intramolecular cyclization of a nitrogen-centered imine radical. These insights into the mechanism pave the way for transformative advancements in this synthesis strategy.

Synthesis of 5-hydroxyisatin thiosemicarbazones, spectroscopic investigation, protein-ligand docking, and in vitro anticancer activity

A series of novel modifications were performed at the N(4) position of 5-hydroxyisatin thiosemicarbazone (TSC). The structure-activity approach is applied to design and synthesize derivatives by condensing thiosemicarbazides with 5-hydroxy isatin. The TSCs were characterized by various spectroscopic techniques viz. FTIR, 1H NMR, 13C NMR, UV-Vis, HRMS data, CHN elemental analysis, and single crystal X-ray diffraction. Biological evaluation of the synthesized compounds revealed the anticancer potency of the TSC analogues against breast cancer (MD-AMD-231, MCF-7), lung cancer (A549, NCI-H460), prostate cancer (PC3), and skin cancer (A431). The molecules, L2, L3, and L6 showed activity in the micromolar range (IC50; 0.19-2.19 μM). L6 exhibited the highest potency against skin cancer A431 cell line, with an IC50 of 0.19 μM compared to 1.8 μM with triapine and showed low toxicity against PNT-2 cells with an SI index of >100 μM. The mechanistic study revealed that L6 inhibited cancer cell proliferation, colony formation, and 3-dimensional spheroid formation by targeting the Ras/MAPK axis. It induced DNA damage and impaired DNA damage repair machinery, which led to the accumulation of DSB. Also, it lowered the ERK1/2 expression, which affected the caspase 3 activity and showed higher binding affinity compared to the FDA-approved drug Lenalidomide in molecular docking studies. Our findings demonstrated the possible future anticancer drug potency of L6 in the skin cancer A431 cells.

Chemical synthesis and application of aryldihydronaphthalene derivatives

Aryldihydronaphthalenes (ADHNs) and their derivatives are widely found in many types of natural products, bioactive compounds, and functional materials, and are also important synthetic intermediates in organic chemistry, attracting widespread attention from both organic and pharmaceutical chemists. In the past two decades, the chemical synthesis and biological activity of ADHNs and their derivatives have become two hot spots. This review summarizes the synthetic protocols of ADHN derivatives, introduces some representative examples of the reaction mechanism, and focuses on the research progress of ADHNs in natural product chemistry and chemical biology since 2000.

Research progress on the pharmacological mechanism, in vivo metabolism and structural modification of Erianin

Erianin is an important bibenzyl compound in dendrobium and has a wide spectrum of pharmacological properties. Since Erianin was discovered, abundant results have been achieved in the in vitro synthesis, structural modification, and pharmacological mechanism research. Researchers have developed a series of simple and efficient in vitro synthesis methods to improve the shortcomings of poor water solubility by replacing the chemical structure or coating it in nanomaterials. Erianin has a broad anti-tumor spectrum and significant anti-tumor effects. In addition, Erianin also has pharmacological actions like immune regulation, anti-inflammatory, and anti-angiogenesis. A comprehensive understanding of the synthesis, metabolism, structural modification, and pharmacological action pathways of Erianin is of great value for the utilization of Erianin. Therefore, this review conducts a relatively systematic look back at Erianin from the above four aspects, to give a reference for the evolvement and further appliance of Erianin.

Synthesis of 1-Aryltetralins via Re2O7/HReO4 Mediated Intramolecular Hydroarylations

Here, we describe highly efficient intramolecular hydroarylations mediated by Re2O7/HReO4. Styrene derivatives of different electronic properties have been activated to effect a challenging intramolecular hydroarylation for the facile access to various substituted 1-aryltetralin structures. This method is characterized by mild reaction conditions, broad substrate scope, high chemical yields, and 100% atom economy. The potential synthetic application of this methodology was exemplified by the efficient total synthesis of an isoCA-4 analogue.

Demonstrating Tumor Vascular Disrupting Activity of the Small-Molecule Dihydronaphthalene Tubulin-Binding Agent OXi6196 as a Potential Therapeutic for Cancer Treatment

The vascular disrupting activity of a promising tubulin-binding agent (OXi6196) was demonstrated in mice in MDA-MB-231 human breast tumor xenografts growing orthotopically in mammary fat pad and syngeneic RENCA kidney tumors growing orthotopically in the kidney. To enhance water solubility, OXi6196, was derivatized as its corresponding phosphate prodrug salt OXi6197, facilitating effective delivery. OXi6197 is stable in water, but rapidly releases OXi6196 in the presence of alkaline phosphatase. At low nanomolar concentrations OXi6196 caused G2/M cell cycle arrest and apoptosis in MDA-MB-231 breast cancer cells and monolayers of rapidly growing HUVECs underwent concentration-dependent changes in their morphology. Loss of the microtubule structure and increased bundling of filamentous actin into stress fibers followed by cell collapse, rounding and blebbing was observed. OXi6196 (100 nM) disrupted capillary-like endothelial networks pre-established with HUVECs on Matrigel®. When prodrug OXi6197 was administered to mice bearing orthotopic MDA-MB-231-luc tumors, dynamic bioluminescence imaging (BLI) revealed dose-dependent vascular shutdown with >80% signal loss within 2 h at doses ≥30 mg/kg and >90% shutdown after 6 h for doses ≥35 mg/kg, which remained depressed by at least 70% after 24 h. Twice weekly treatment with prodrug OXi6197 (20 mg/kg) caused a significant tumor growth delay, but no overall survival benefit. Similar efficacy was observed for the first time in orthotopic RENCA-luc tumors, which showed massive hemorrhage and necrosis after 24 h. Twice weekly dosing with prodrug OXi6197 (35 mg/kg) caused tumor growth delay in most orthotopic RENCA tumors. Immunohistochemistry revealed extensive necrosis, though with surviving peripheral tissues. These results demonstrate effective vascular disruption at doses comparable to the most effective vascular-disrupting agents (VDAs) suggesting opportunities for further development.

Direct activation of alcohols via perrhenate ester formation for an intramolecular dehydrative Friedel–Crafts reaction

A general and highly efficient intramolecular dehydrative Friedel–Crafts reactions via Re2O7 mediated hydroxyl group activation is described for the syntheses of tetrahydronaphthalene, tetrahydroquinoline, tetrahydroisoquinoline, chromane, and isochromane derivatives.

Ag(I)-Catalyzed/Acid-Mediated Cascade Cyclization of ortho-Alkynylaryl-1,3-dicarbonyls to Access Arylnaphthalenelactones and Furanonaphthol Libraries via Aryl-Disengagement

ortho-Alkynylarylketone derivatives were employed as key precursors for a one-pot synthesis of arylnaphthalenelactone and furanonaphthol libraries. In this work, we discovered a cost-effective protocol to prepare arylnaphthalenelactones in one-pot using inexpensive starting material, malonate ester, which was conveniently functionalized leading to a variety of structures. Moreover, we also found an unexpected oxy-dearylation reaction which could be used to synthesize furanonaphthol analogs. These novel methods could be applied to a broad range of substrates to give the corresponding products in up to 83% yield. Notably, these classes of compounds exhibited more significant inhibition against protein-tyrosine phosphatase 1B (PTP1B) enzyme than a standard compound, ursolic acid.

Anticancer properties of indole derivatives as IsoCombretastatin A-4 analogues

In this study, a variety of original ligands related to Combretastatin A-4 and isoCombretastatin A-4, able to inhibit the tubulin polymerization into microtubules, was designed, synthesized, and evaluated. Our lead compound 15d having a quinazoline as A-ring and a 2-substituted indole as B-ring separated by a N-methyl linker displayed a remarkable sub-nanomolar level of cytotoxicity (IC₅₀ < 1 nM) against 9 human cancer cell lines.

Synthesis and Anticancer Properties of Oxazepines Related to Azaisoerianin and IsoCoQuines

In this article, we report the synthesis and biological properties of a series of novel oxazepines related to isoCA-4 having significant antitumor properties. Among them, three oxazepin-9-ol derivatives display a nanomolar or a sub-nanomolar cytotoxicity level against five human cancer cell lines (HCT116, U87, A549, MCF7, and K562). It was demonstrated that the lead compound in this series inhibits tubulin assembly with an IC₅₀ value of 1 μM and totally arrests the cellular cycle in the G2/M phase at the low concentration of 5 nM in HCT116 and K562 cells. Molecular modeling studies perfectly corroborates these promising results.

One-pot synthesis of thiazolo[3,2-a]pyrimidine derivatives, their cytotoxic evaluation and molecular docking studies

An economical, simple and efficient one-pot method has been developed for the synthesis of thiazolo[3,2-a]pyrimidine hydrobromide derivatives. 2,4-diaryl-6,7,8,9-tetrahydro-4H-benzo[4,5]thiazolo[3,2-a]pyrimidine hydrobromides were synthesized by the α-bromination of cyclohexanone with N-Bromosuccinamide (NBS) and followed by cyclization with 3,4-dihydropyrimidine-2(1H)-thiones, respectively, in the presence of p-toluenesulfonic acid (PTSA) in acetonitrile. However when cyclohexanone was replaced by acetyl acetone and alpha-tetralone gave the corresponding 1-(3-methyl-5,7-diaryl-5H-thiazolo[3,2-a]pyrimidin-2-yl)ethan-1-one hydrobromide and 9,11-diaryl-6,11-dihydro-5H-naphtho[1',2':4,5]thiazolo[3,2-a]pyrimidine hydrobromide derivatives, respectively. The significant features of this method are novel, simple, inexpensive experimental procedure, short reaction time, and good yield. The some of the synthesized compounds were evaluated for cytotoxic activity against human lung adenocarcinoma cell line (A549), human breast carcinoma cell line (MCF-7), human cervical cancer cell line (HeLa) and human neuronal carcinoma cell lines (SKNSH). Tested compounds 5(b-e) showed the excellent anticancer activity against various cell lines. Particularly compound 5c with IC₅₀ value of 2.2 ± 0.6 μM against A549 and compound 5e with IC₅₀ value of 5.6 ± 0.4 μM against HeLa showed best cytotoxic effects. Furthermore, Molecular docking study was performed for some of the synthesized compounds 5(b-e) against topoisomerase-II by using Auto dock method. Docking results of the compounds 5c, 5d, and 5e exhibited higher cytotoxic activity than the standard doxorubicin.

Exploring Diverse-Ring Analogues on Combretastatin A4 (CA-4) Olefin as Microtubule-Targeting Agents

Combretastatin-4 (CA-4) as a tubulin polymerization inhibitor draws extensive attentions. However, due to its weak stability of cis-olefin and poor metabolic stability, structure modifications on cis-configuration are being performed. In this work, we constructed a series of novel CA-4 analogues with linkers on olefin containing diphenylethanone, cis-locked dihydrofuran, α-substituted diphenylethanone, cyclobutane and cyclohexane on its cis-olefin. Cytotoxic activity of all analogues was measured by an SRB assay. Among them, compound 6b, a by-product in the preparation of diphenylethanone analogues, was found to be the most potent cytotoxic agents against HepG2 cells with IC₅₀ values of less than 0.5 μM. The two isomers of 6b induced cellular apoptosis tested by Annexin V-FITC and propidium iodide (PI) double staining, arrested cells in the G2/M phase by PI staining analysis, and disrupted microtubule network by immunohistochemistry study in HepG2 cells. Moreover, 6b-(E) displayed a dose-dependent inhibition effect for tubulin assembly in in vitro tubulin polymerization assay. In addition, molecular docking studies showed that two isomers of 6b could bind efficiently at colchicine binding site of tubulin similar to CA-4.

Combretastatin analogues in cancer biology: A prospective view

The stilbenoid combretastatin and its derivatives are potent inhibitors of angiogenesis and cell proliferation and induce apoptosis. They disrupt cytoskeletal dynamics and modulate cell morphology, motility, and invasion. Hence they have been viewed as potential as anticancer agents. The impediments of poor solubility and bioavailability and the spontaneous geometric isomerisation of combretastatin into an inactive form have led to intensive efforts towards evolving novel analogues to provide more efficacious biological outcome. Importantly, isomerically stable and biologically active cis-restricted analogues have been synthesised and tested. However, very few analogues have been tested in preclinical models to assess their effects on processes relevant to cancer development and progression. Hence the accent here is on the signalling systems operated by the new derivatives and their biological effects with reference to cancer progression. Combretastatins modulate an extensive network of signalling emphasising their varied versatility. Harnessing these systems and accentuating or counteracting aberrant signalling could open potential avenues of approach to the designing of novel derivatives with enhanced performance. The import of mammalian target of rapamycin pathway, which co-ordinates growth factor receptor signalling, epithelial-mesenchymal transition activation and angiogenic signalling, is emphasised. It may be viewed as a prime target for allosteric inhibition in combination with combretastatin analogues to ascertain their potential in cancer control.

Structure Guided Design, Synthesis, and Biological Evaluation of Novel Benzosuberene Analogues as Inhibitors of Tubulin Polymerization

A promising design paradigm for small-molecule inhibitors of tubulin polymerization that bind to the colchicine site draws structural inspiration from the natural products colchicine and combretastatin A-4 (CA4). Our previous studies with benzocycloalkenyl and heteroaromatic ring systems yielded promising inhibitors with dihydronaphthalene and benzosuberene analogues featuring phenolic (KGP03 and KGP18) and aniline (KGP05 and KGP156) congeners emerging as lead agents. These molecules demonstrated dual mechanism of action, functioning both as potent vascular disrupting agents (VDAs) and as highly cytotoxic anticancer agents. A further series of analogues was designed to extend functional group diversity and investigate regioisomeric tolerance. Ten new molecules were effective inhibitors of tubulin polymerization (IC₅₀ < 5 μM) with seven of these exhibiting highly potent activity comparable to CA4, KGP18, and KGP03. For one of the most effective agents, dose-dependent vascular shutdown was demonstrated using dynamic bioluminescence imaging in a human prostate tumor xenograft growing in a rat.

1,1-Diheterocyclic Ethylenes Derived from Quinaldine and Carbazole as New Tubulin-Polymerization Inhibitors: Synthesis, Metabolism, and Biological Evaluation

We report the synthesis and metabolic and biological evaluation of a series of 17 novel heterocyclic derivatives of isocombretastatin-A4 (iso-CA-4) and their structure-activity relationships. Among these derivatives, the most active compound, 4f, inhibited the growth of a panel of seven cancer cell lines with an IC₅₀ in the low nanomolar range. In addition, 4f showed interesting activity against CA-4-resistant colon-carcinoma cells and multidrug-resistant leukemia cells. It also induced G₂/M cell-cycle arrest. Structural data indicated binding of 4f to the colchicine site of tubulin, likely preventing the curved-to-straight tubulin structural changes that occur during microtubule assembly. Also, 4f disrupted the blood-vessel-like assembly formed by human umbilical-vein endothelial cells in vitro, suggesting its function as a vascular-disrupting agent. An in vitro metabolism study of 4f showed its high human-microsomal stability in comparison with that of iso-CA-4. The physicochemical properties of 4f may be conducive to CNS permeability, suggesting that this compound may be a possible candidate for the treatment of glioblastoma.

Efficient Synthetic Methodology for the Construction of Dihydronaphthalene and Benzosuberene Molecular Frameworks

Benzosuberene analogues (1 and 2) and dihydronaphthalene analogues (3 and 4) function as potent inhibitors of tubulin polymerization, demonstrate pronounced cytotoxicity (low nM to pM range) against human cancer cell lines, and are promising vascular disrupting agents (VDAs). As such, these compounds represent lead anticancer agents with potential translatability towards the clinic. Methodology previously established by us (and others) facilitated synthetic access to a variety of structural and functional group modifications necessary to explore structure activity relationship considerations directed towards the development of these (and related) molecules as potential therapeutic agents. During the course of these studies it became apparent that the availability of synthetic methodology to facilitate direct conversion of the phenolic-based compounds to their corresponding aniline congeners would be beneficial. Accordingly, modified synthetic routes toward these target phenols (benzosuberene 1 and dihydronaphthalene 3) were developed in order to improve scalability and overall yield [45-57% (1) and 32% (3)]. Moreover, benzosuberene-based phenolic analogue 1 and separately dihydronaphthalene-based phenolic analogue 3 were successfully converted into their corresponding aniline analogues 2 and 4 in good yield (>60% over three steps) using a palladium catalyzed amination reaction.

Design, synthesis and biological evaluation of quinoline-indole derivatives as anti-tubulin agents targeting the colchicine binding site

A series of novel isocombretastatin A-4 (isoCA-4) analogs were designed and synthesized by replacing 3,4,5-trimethoylphenyl and isovanillin of isoCA-4 with quinoline and indole moieties, respectively. The structure activity relationships (SARs) of these synthesized quinoline-indole derivatives have been intensively investigated. Two compounds 27c and 34b exhibited the most potent activities against five cancer cell lines with IC₅₀ values ranging from 2 to 11 nM, which were comparable to those of Combretastatin A-4 (CA-4, 1). Further mechanism investigations revealed that 34b effectively inhibited the microtubule polymerization by binding to the colchicine site of tubulin. Further cellular mechanism studies elucidated that 34b disrupted cell microtubule networks, arrested the cell cycle at G2/M phase, induced apoptosis and depolarized mitochondria of K562 cells. Moreover, 34b displayed potent anti-vascular activity in both wound healing and tube formation assays. Importantly, 27c and 34b significantly inhibited tumor growth in H22 xenograft models without apparent toxicity, suggesting that 27c and 34b deserve further research as potent antitumor agents for cancer therapy.

Discovery of Novel 4-Arylisochromenes as Anticancer Agents Inhibiting Tubulin Polymerization

XJP-L (8), a derivative of the natural product (±)-7,8-dihydroxy-3-methylisochroman-4-one isolated from the peel of Musa sapien tum L., was found to exhibit weak inhibitory activity of tubulin polymerization (IC₅₀ = 10.6 μM) in our previous studies. Thus, a series of 4-arylisochromene derivatives were prepared by incorporating the trimethoxyphenyl moiety into 8, among which compound (±)-19b was identified as the most potent compound with IC₅₀ values ranging from 10 to 25 nM against a panel of cancer cell lines. Further mechanism studies demonstrated that (±)-19b disrupted the intracellular microtubule network, caused G2/M phase arrest, induced cell apoptosis, and depolarized mitochondria of K562 cells. Moreover, (±)-19b exhibited potent in vitro antivascular and in vivo antitumor activities. Notably, the R-configured enantiomer of (±)-19b, which was prepared by chiral separation, was slightly more potent than (±)-19b and was much more potent than the S-configured enantiomer in both antiproliferative and antitubulin assays. Our findings suggest that (±)-19b deserves further research as a potential antitubulin agent for the treatment of cancers.

Synthesis of dihydronaphthalene analogues inspired by combretastatin A-4 and their biological evaluation as anticancer agents

The natural products colchicine and combretastatin A-4 (CA4) have provided inspiration for the discovery and development of a wide array of derivatives and analogues that inhibit tubulin polymerization through a binding interaction at the colchicine site on β-tubulin. A water-soluble phosphate prodrug salt of CA4 (referred to as CA4P) has demonstrated the ability to selectively damage tumor-associated vasculature and ushered in a new class of developmental anticancer agents known as vascular disrupting agents (VDAs). Through a long-term program of structure activity relationship (SAR) driven inquiry, we discovered that the dihydronaphthalene molecular scaffold provided access to small-molecule inhibitors of tubulin polymerization. In particular, a dihydronaphthalene analogue bearing a pendant trimethoxy aryl ring (referred to as KGP03) and a similar aroyl ring (referred to as KGP413) were potent inhibitors of tubulin polymerization (IC50 = 1.0 and 1.2 μM, respectively) and displayed low nM cytotoxicity against human cancer cell lines. In order to enhance water-solubility for in vivo evaluation, the corresponding phosphate prodrug salts (KGP04 and KGP152, respectively) were synthesized. In a preliminary in vivo study in a SCID-BALB/c mouse model bearing the human breast tumor MDA-MB-231-luc, a 99% reduction in signal was observed with bioluminescence imaging (BLI) 4 h after IP administration of KGP152 (200 mg kg-1) indicating reduced tumor blood flow. In a separate study, disruption of tumor-associated blood flow in a Fischer rat bearing an A549-luc human lung tumor was observed by color Doppler ultrasound following administration of KGP04 (15 mg kg-1).

Visible light catalyzed reaction of α-bromochalcones with chalcones: direct access to the urundeuvine scaffold

The α-keto vinyl radicals generated from α-bromochalcones under visible light photoredox catalyzed conditions were trapped by chalcones.

Synthesis, biological evaluation and molecular docking studies of a new series of chalcones containing naphthalene moiety as anticancer agents

A series of chalcones containing naphthalene moiety 4a-4p have been synthesized, characterized by ¹H NMR and ¹³C NMR and evaluated for their in vitro anticancer activity. The majority of the screened compounds displayed potent anticancer activity against both HCT116 and HepG2 human cancer cell lines. Among the series, compound 4h with a diethylamino group at the para position of the phenyl ring exhibited the most potent anticancer activity against HCT116 and HepG2 cell lines with IC₅₀ values of 1.20 ± 0.07 and 1.02 ± 0.04 μM, respectively. The preliminary structure-activity relationship has been summarized. Tubulin polymerization experiments indicated that 4h effectively inhibited tubulin polymerization and flow cytometric assay revealed that 4h arrests HepG2 cells at the G2/M phase in a dose-dependent manner. Furthermore, molecular docking studies suggested that 4h binds to the colchicine binding site of tubulin.

Constructing novel dihydrofuran and dihydroisoxazole analogues of isocombretastatin-4 as tubulin polymerization inhibitors through [3+2] reactions

[3+2] reactions play a key role in constructing various pharmaceutical moleculars. In this study, using Mn(OAc)₃ mediated and 1,3-dipolar [3+2] cyclization reactions, 38 novel dihydrofuran and dihydroisoxazole analogues of isoCA-4 were synthesized as inhibitors of tubulin polymerization. Among them, compound 6g was found to be the most potent cytotoxic agents against PC-3 cells with IC₅₀ value of 0.47μM, and compound 5p exhibted highest activity on HeLa cells with IC₅₀ vaule of 2.32µM. Tubulin polymerization assay revealed that 6g was a dose-dependent and effective inhibitor of tubulin assembly. Immunohistochemistry studies and cell cycle distribution analysis indicated that 6g severely disrupted microtubule network and significantly arrested most cells in the G2/M phase of the cell cycle in PC-3 cells. In addition, molecular docking studies showed that two chiral isomers of 6g can bind efficiently and similarly at colchicine binding site of tubulin.

Tubulin inhibitors targeting the colchicine binding site: a perspective of privileged structures

The vital roles of microtubule in mitosis and cell division make it an attractive target for antitumor therapy. Colchicine binding site of tubulin is one of the most important pockets that have been focused on to design tubulin-destabilizing agents. Over the past few years, a large number of colchicine binding site inhibitors (CBSIs) have been developed inspired by natural products or synthetic origins, and many moieties frequently used in these CBSIs are structurally in common. In this review, we will classify the CBSIs into classical CBSIs and nonclassical CBSIs according to their spatial conformations and binding modes with tubulin, and highlight the privileged structures from these CBSIs in the development of tubulin inhibitors targeting the colchicine binding site.

Design, synthesis and anticancer properties of IsoCombretaQuinolines as potent tubulin assembly inhibitors

The synthesis and evaluation of a new series of IsoCombretaQuinolines (IsoCoQuines) 2 with a 2-substituted-quinoline in place of the 3,4,5-trimethoxyphenyl ring present in isoCA-4 and CA-4 are described. Most of these compounds displayed a potent cytotoxic activity (IC₅₀ < 10 nM) against a panel of five human cancer cell lines and inhibited tubulin assembly at a micromolar level. The most potent analogue 2b, having a 3-hydroxy-4-methoxyphenyl as B-ring, led to cell cycle arrest in G2/M phase. Docking studies indicate that 2b showed a binding mode comparable to those previously observed with quinazoline analogous (IsoCoQ) and with isoCA-4 at the colchicine binding site of tubulin.

Design, Synthesis and Biological Evaluation of Benzohydrazide Derivatives Containing Dihydropyrazoles as Potential EGFR Kinase Inhibitors

A series of novel benzohydrazide derivatives containing dihydropyrazoles have been synthesized as potential epidermal growth factor receptor (EGFR) kinase inhibitors and their biological activities as potential antiproliferative agents have been evaluated. Among these compounds, compound H20 exhibited the most potent antiproliferative activity against four cancer cell line variants (A549, MCF-7, HeLa, HepG2) with IC₅₀ values of 0.46, 0.29, 0.15 and 0.21 μM respectively, which showed the most potent EGFR inhibition activities (IC₅₀ = 0.08 μM for EGFR). Molecular modeling simulation studies were performed in order to predict the biological activity and activity relationship (SAR) of these benzohydrazide derivatives. These results suggested that compound H20 may be a promising anticancer agent.

Facile Synthesis of Natural Alkoxynaphthalene Analogues from Plant Alkoxybenzenes

Analogues of the bioactive natural alkoxynaphthalene pycnanthulignene D were synthesized by an efficient method. The starting plant allylalkoxybenzenes (1) are easily available from the plant essential oils of sassafras, dill, and parsley. The target 1-arylalkoxynaphthalenes (5) exhibited antiproliferative activity in a phenotypic sea urchin embryo assay.

Design, synthesis, and biological evaluation of water-soluble amino acid prodrug conjugates derived from combretastatin, dihydronaphthalene, and benzosuberene-based parent vascular disrupting agents

Targeting tumor vasculature represents an intriguing therapeutic strategy in the treatment of cancer. In an effort to discover new vascular disrupting agents with improved water solubility and potentially greater bioavailability, various amino acid prodrug conjugates (AAPCs) of potent amino combretastatin, amino dihydronaphthalene, and amino benzosuberene analogs were synthesized along with their corresponding water-soluble hydrochloride salts. These compounds were evaluated for their ability to inhibit tubulin polymerization and for their cytotoxicity against selected human cancer cell lines. The amino-based parent anticancer agents 7, 8, 32 (also referred to as KGP05) and 33 (also referred to as KGP156) demonstrated potent cytotoxicity (GI50=0.11-40nM) across all evaluated cell lines, and they were strong inhibitors of tubulin polymerization (IC50=0.62-1.5μM). The various prodrug conjugates and their corresponding salts were investigated for cleavage by the enzyme leucine aminopeptidase (LAP). Four of the glycine water-soluble AAPCs (16, 18, 44 and 45) showed quantitative cleavage by LAP, resulting in the release of the highly cytotoxic parent drug, whereas partial cleavage (<10-90%) was observed for other prodrugs (15, 17, 24, 38 and 39). Eight of the nineteen AAPCs (13-16, 42-45) showed significant cytotoxicity against selected human cancer cell lines. The previously reported CA1-diamine analog and its corresponding hydrochloride salt (8 and 10, respectively) caused extensive disruption (at a concentration of 1.0μM) of human umbilical vein endothelial cells growing in a two-dimensional tubular network on matrigel. In addition, compound 10 exhibited pronounced reduction in bioluminescence (greater than 95% compared to saline control) in a tumor bearing (MDA-MB-231-luc) SCID mouse model 2h post treatment (80mg/kg), with similar results observed upon treatment (15mg/kg) with the glycine amino-dihydronaphthalene AAPC (compound 44). Collectively, these results support the further pre-clinical development of the most active members of this structurally diverse collection of water-soluble prodrugs as promising anticancer agents functioning through a mechanism involving vascular disruption.

IsoCombretaQuinazolines: Potent Cytotoxic Agents with Antitubulin Activity

A series of novel isocombretaquinazolines (isoCoQ) 4 were quickly prepared by coupling N-toluenesulfonylhydrazones with 4-chloroquinazolines under palladium catalysis. These compounds, which can be regarded as isocombretastatin A-4 (isoCA-4) analogues that lack the 3,4,5-trimethoxyphenyl ring, displayed nanomolar-level cytotoxicity against various human cancer cell lines and were observed to effectively inhibit tubulin polymerization. The isoCoQ compounds 2-methoxy-5-(1-(2-methylquinazolin-4-yl)vinyl)phenol (4 b), 4-[1-(3-fluoro-4-methoxyphenyl)vinyl]-2-methylquinazoline (4 c), and 2-methoxy-5-(1-(2-methylquinazolin-4-yl)vinyl)aniline (4 d), which respectively bear the greatest resemblance to isoCA-4, isoFCA-4, and isoNH2 CA-4, are able to arrest HCT116 cancer cells in the G2 /M cell-cycle phase at very low concentrations. Preliminary in vitro antivascular assay results show that 4 d is able to disrupt a network of capillary-like structures formed by human umbilical vein endothelial cells on Matrigel. All these results clearly demonstrate that replacement of the 3,4,5-trimethoxyphenyl ring of isoCA-4 with a quinazoline nucleus is a feasible approach toward new and highly promising derivatives with the potential for further development as antitubulin agents.

Synthesis and evaluation of naphthalene-based thiosemicarbazone derivatives as new anticancer agents against LNCaP prostate cancer cells

Fourteen new naphthalene-based thiosemicarbazone derivatives were designed as anticancer agents against LNCaP human prostate cancer cells and synthesized. MTT assay indicated that compounds 6, 8 and 11 exhibited inhibitory effect on LNCaP cells. Among these compounds, 4-(naphthalen-1-yl)-1-[1-(4-hydroxyphenyl)ethylidene)thiosemicarbazide (6), which caused more than 50% death on LNCaP cells, was chosen for flow cytometric analysis of apoptosis. Flow cytometric analysis pointed out that compound 6 also showed apoptotic effect on LNCaP cells. Compound 6 can be considered as a promising anticancer agent against LNCaP cells owing to its potent cytotoxic activity and apoptotic effect.