Synthesis and Cytotoxic Evaluation of Novel Dimethyl [1,1′-Biphenyl]-2,2′-dicarboxylates Bearing 1,3,4-Thiadiazole Moieties

TMSCl Promoted Direct Conversion of Cyclic Anhydrides to (Un)Symmetric-Diesters/Amide Esters

We present a mild, efficient, and one-pot method for the silyl-promoted transformation of cyclic anhydrides into homo- and hetero-dicarboxylic acid diesters and amide esters. This versatile reaction operates under ambient conditions, on a gram scale, and accommodates a wide range of alcohols, amines, and cyclic anhydrides. The one-pot process involves a two-step sequence, starting with the nucleophilic opening of anhydride by an amine or alcohol, followed by esterification. TMSCl serves a dual role, acting as a sacrificial reagent to remove in situ water and as a Lewis acid to promote the anhydride opening. The reaction proceeds successfully in the absence and presence of a base, as confirmed by NMR and crossover experiments, which validated the formation of dicarboxylic acid monoester and alkyl silyl mixed diester respectively. Controlled experiments have shown that the one-pot process yields higher efficiencies when compared to the same reaction conducted using a two-step process. This is the first comprehensive study demonstrating a broad substrate scope for the conversion of cyclic anhydride into diesters and amide esters. The method finds application in the synthesis of various commercial plasticizers.

Antiproliferative Noscapinoids Bearing an Amidothiadiazole Scaffold as Apoptosis Inducers: Design, Synthesis and Molecular Docking

Noscapine an FDA-approved antitussive agent. With low cytotoxicity with higher concentrations, noscapine and its derivatives have been shown to have exceptional anticancer properties against a variety of cancer cell lines. In order to increase its potency, in this study, we synthesized a series of new amido-thiadiazol coupled noscapinoids and tested their cytotoxicity in vitro. All of the newly synthesised compounds demonstrated potent cytotoxic potential, with IC₅₀ values ranging from 2.1 to 61.2 μM than the lead molecule, noscapine (IC₅₀ value ranges from 31 to 65.5 μM) across all cell lines, without affecting normal cells (IC₅₀ value is>300 μM). Molecular docking of all these molecules with tubulin (PDB ID: 6Y6D, resolution 2.20 Å) also revealed better binding affinity (docking score range from -5.418 to -9.679 kcal/mol) compared to noscapine (docking score is -5.304 kcal/mol). One of the most promising synthetic derivatives 6aa (IC₅₀ value ranges from 2.5 to 7.3 μM) was found to bind tubulin with the highest binding affinity (ΔG_binding is -28.97 kcal/mol) and induced apoptosis in cancer cells more effectively.

Discovery and Anticancer Activity of Novel 1,3,4-Thiadiazole- and Aziridine-Based Indolin-2-ones via In Silico Design Followed by Supramolecular Green Synthesis

Three crucial anticancer scaffolds, namely indolin-2-one, 1,3,4-thiadiazole, and aziridine, are explored to synthesize virtually screened target molecules based on the c-KIT kinase protein. The stem cell factor receptor c-KIT was selected as target because most U.S. FDA-approved receptor tyrosine kinase inhibitors bearing the indolin-2-one scaffold profoundly inhibit c-KIT. Molecular hybrids of indolin-2-one with 1,3,4-thiadiazole (IIIa-m) and aziridine (VIa and VIc) were afforded through a modified Schiff base green synthesis using β-cyclodextrin-SO₃H in water as a recyclable proton-donor catalyst. A computational study found that indolin-2,3-dione forms a supramolecular inclusion complex with β-cyclodextrin-SO₃H through noncovalent interactions. A molecular docking study of all the synthesized compounds was executed on the c-KIT kinase domain, and most compounds displayed binding affinities similar to that of Sunitinib. On the basis of the pharmacokinetic significance of the aryl thioether linkage in small molecules, 1,3,4-thiadiazole hybrids (IIIa-m) were extended to a new series of 3-((5-(phenylthio)-1,3,4-thiadiazol-2-yl)imino)indolin-2-ones (IVa-m) via thioetherification using bis(triphenylphosphine)palladium(II)dichloride as the catalyst for C-S bond formation. Target compounds were tested against NCI-60 human cancer cell lines for a single-dose concentration. Among all three series of indolin-2-ones, the majority of compounds demonstrated broad-spectrum activity toward various cancer cell lines. Compounds IVc and VIc were further evaluated for a five-dose anticancer study. Compound IVc showed a potent activity of IC₅₀ = 1.47 μM against a panel of breast cancer cell lines, whereas compound VIc exhibited the highest inhibition for a panel of colon cancer cell lines at IC₅₀ = 1.40 μM. In silico ADME property descriptors of all the target molecules are in an acceptable range. Machine learning algorithms were used to examine the metabolites and phase I and II regioselectivities of compounds IVc and VIc, and the results suggested that these two compounds could be potential leads for the treatment of cancer.

Potent Inhibition of Nitric Oxide-Releasing Bifendate Derivatives against Drug-Resistant K562/A02 Cells in Vitro and in Vivo

Multidrug resistance is a major obstacle to successful chemotherapy for leukemia. In this study, a series of nitric oxide (NO)-releasing bifendate derivatives (7a-n) were synthesized. Biological evaluation indicated that the most active compound (7a) produced relatively high levels of NO and significantly inhibited the proliferation of drug-resistant K562/A02 cells in vitro and in vivo. In addition, 7a induced the mitochondrial tyrosine nitration and the intracellular accumulation of rhodamine 123 by inhibiting P-gp activity in K562/A02 cells. Furthermore, 7a remarkably down-regulated AKT, NF-κB, and ERK activation and HIF-1α expression in K562/A02 cells, which are associated with the tumor cell proliferation and drug resistance. Notably, the antitumor effects were dramatically attenuated by an NO scavenger or elimination of the NO-releasing capability of 7a, indicating that NO produced by 7a contributed to, at least partly, its cytotoxicity against drug-resistant K562/A02 cells. Overall, 7a may be a potential agent against drug-resistant myelogenous leukemia.

Anticancer efficacy of a nitric oxide-modified derivative of bifendate against multidrug-resistant cancer cells

The development of multidrug resistance (MDR) not only actively transports a wide range of cytotoxic drugs across drug transporters but is also a complex interaction between a number of important cellular signalling pathways. Nitric oxide donors appear to be a new class of anticancer therapeutics for satisfying all the above conditions. Previously, we reported furoxan‐based nitric oxide‐releasing compounds that exhibited selective antitumour activity in vitro and in vivo. Herein, we demonstrate that bifendate (DDB)‐nitric oxide, a synthetic furoxan‐based nitric oxide‐releasing derivative of bifendate, effectively inhibits the both sensitive and MDR tumour cell viability at a comparatively low concentration. Interestingly, the potency of DDB‐nitric oxide is the independent of inhibition of the functions and expressions of three major ABC transporters. The mechanism of DDB‐nitric oxide appears to be in two modes of actions by inducing mitochondrial tyrosine nitration and apoptosis, as well as by down‐regulating HIF‐1α expression and protein kinase B (AKT), extracellular signal‐regulated kinases (ERK), nuclear factor κB (NF‐κB) activation in MDR cells. Moreover, the addition of a typical nitric oxide scavenger significantly attenuated all the effects of DDB‐nitric oxide, indicating that the cytotoxicity of DDB‐nitric oxide is as a result of higher levels of nitric oxide release in MDR cancer cells. Given that acquired MDR to nitric oxide donors is reportedly difficult to achieve and genetically unstable, compound like DDB‐nitric oxide may be a new type of therapeutic agent for the treatment of MDR tumours.

Synthesis and biological evaluation of bifendate-chalcone hybrids as a new class of potential P-glycoprotein inhibitors

Overexpression of P-glycoprotein (P-gp) is one of the major problems to successful cancer chemotherapy. To find novel effective P-gp inhibitors, a series of bifendate-chalcone hybrids were synthesized and evaluated. Among them, the most active compound 8g had little intrinsic cytotoxicity (IC(50)>200 μM), and could increase accumulation of Rhodamine 123 in K562/A02 cells more potently than bifendate and verapamil (VRP) by inhibiting P-gp efflux function. And 8g displayed potent chemo-sensitizing effect and persisted for much longer time (>24h) compared with VRP (<6h). In addition, 8g, unlike VRP, showed no stimulation on the P-gp ATPase activity, suggesting it is not a P-gp substrate. Therefore, 8g may represent a promising lead to develop MDR reversal agents for cancer chemotherapy.