Heterocyclic thrombin inhibitors. Part 2: quinoxalinone derivatives as novel, potent antithrombotic agents

Metal- and photocatalyst-free approach to visible-light-induced acylation of quinoxalinones

A transition-metal- and photocatalyst-free photochemical reaction was successfully developed for the direct acylation of quinoxalin-2(1H)-ones, which was enabled by the formation of electron donor-acceptor (EDA) complexes. The use of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the electron donor allows efficient and operationally simple access to a series of C3-aroylated and acylated quinoxalin-2(1H)-ones with moderate to good yields.

Design, synthesis, and molecular docking studies of diphenylquinoxaline-6-carbohydrazide hybrids as potent α-glucosidase inhibitors

A novel series of diphenylquinoxaline-6-carbohydrazide hybrids 7a–o were rationally designed and synthesized as anti-diabetic agents. All synthesized compounds 7a–o were screened as possible α-glucosidase inhibitors and exhibited good inhibitory activity with IC₅₀ values in the range of 110.6 ± 6.0 to 453.0 ± 4.7 µM in comparison with acarbose as the positive control (750.0 ± 10.5 µM). An exception in this trend came back to a compound 7k with IC₅₀ value > 750 µM. Furthermore, the most potent derivative 7e bearing 3-fluorophenyl moiety was further explored by kinetic studies and showed the competitive type of inhibition. Additionally, the molecular docking of all derivatives was performed to get an insight into the binding mode of these derivatives within the active site of the enzyme. In silico assessments exhibited that 7e was well occupied in the binding pocket of the enzyme through favorable interactions with residues, correlating to the experimental results.

Functionalized quinoxalinones as privileged structures with broad-ranging pharmacological activities

Quinoxalinones are a class of heterocyclic compounds which attract extensive attention owing to their potential in the field of organic synthesis and medicinal chemistry. During the past few decades, many new synthetic strategies toward the functionalization of quinoxalinone based scaffolds have been witnessed. Regrettably, there are only a few reports on the pharmacological activities of quinoxalinone scaffolds from a medicinal chemistry perspective. Therefore, herein we intend to outline the applications of multifunctional quinoxalinones as privileged structures possessing various biological activities, including anticancer, neuroprotective, antibacterial, antiviral, antiparasitic, anti-inflammatory, antiallergic, anti-cardiovascular, anti-diabetes, antioxidation, etc. We hope that this review will facilitate the development of quinoxalinone derivatives in medicinal chemistry.

Photoinitiated decarboxylative C3-difluoroarylmethylation of quinoxalin-2(1H)-ones with potassium 2,2-difluoro-2-arylacetates in water

An efficient visible-light-induced decarboxylative C3-difluoroarylmethylation of quinoxalin-2(1H)-one with potassium 2,2-difluoro-2-arylacetate in water at room temperature was developed.

Recent advances in the direct functionalization of quinoxalin-2(1H)-ones

The direct C3-functionalization of quinoxalin-2(1H)-ones via C-H bond activation has recently attracted considerable attention, due to their diverse biological activities and chemical properties. This review will focus on the recent achievements, mainly including arylation, alkylation, acylation, alkoxycarbonylation, amination, amidation and phosphonation of quinoxalin-2(1H)-ones. Their mechanisms are also discussed.

Design, synthesis, in silico docking studies and biological evaluation of novel quinoxaline-hydrazide hydrazone-1,2,3-triazole hybrids as α-glucosidase inhibitors and antioxidants

Novel quinoxaline-hydrazidehydrazone-1,2,3-triazole hybrids were synthesized, characterized and screened for α-glucosidase inhibitory and antioxidant activities.

Synthesis and Biological Evaluation of 2-Oxo/Thioxoquinoxaline and 2-Oxo/Thioxoquinoxaline-Based Nucleoside Analogues

Several O- and S-quinoxaline glycosides have been prepared by glycosidation of 3-methyl-2-oxo(thioxo)-1,2-dihydroquinoxalines 1a,b with α-D-glucopyranosyl, α-D-galactopyranosyl, and α-D-lactosyl bromide in the presence of K2CO3 followed by deacetylation with Et3N/H2O. Furthermore, alkylation of 1a,b with 4-bromobutyl acetate, 2-acetoxyethoxymethyl bromide, and 3-chloropropanol afforded the corresponding O- and S-acycloquinoxaline nucleosides. Reaction of 1b with chloroacetic acid followed by condensation with sulfacetamide and sulfadiazine in the presence of Et3N/THF and ethyl chloroformate gave the corresponding sulfonamide derivatives 14 and 15, respectively. The structures of new compounds were confirmed by using IR, (1)H, (13)C NMR spectra and microanalysis. Some of these compounds were screened in vitro for antitumor and antifungal activities.

Microwave-Assisted Multicomponent Synthesis of Dihydroquinoxalinones on Soluble Polymer Support

A one-pot and two-step reaction of four components, including aldehydes, Fmoc-protected α-amino acid, isocyanide, and soluble polymer-supported 4-fluoro-3-amino benzoate ester, was developed for an efficient synthesis of dihydroquinoxalinones under microwave irradiation. Fmoc deprotection followed by intramolecular cyclization of the diamide gave a facile access to novel bicyclic quinoxalin-2-ones. On the basis of this approach, a new route to synthesize this privileged scaffold from the diamide intermediate was designed and accomplished with high yields. Use of multicomponent reaction (MCR) has been shown to display a good functional group tolerance, while the product isolation and purification is straightforward by precipitation and washings. Current library discusses the synthesis and diversification of 21 compounds produced using this strategy.

Spectral and kinetic properties of radicals derived from oxidation of quinoxalin-2-one and its methyl derivative

The kinetics and spectral characteristics of the transients formed in the reactions of •OH and •N3 with quinoxalin-2(1H)-one (Q), its methyl derivative, 3-methylquinoxalin-2(1H)-one (3-MeQ) and pyrazin-2-one (Pyr) were studied by pulse radiolysis in aqueous solutions at pH 7. The transient absorption spectra recorded in the reactions of •OH with Q and 3-MeQ consisted of an absorption band with λmax = 470 nm assigned to the OH-adducts on the benzene ring, and a second band with λmax = 390 nm (for Q) and 370 nm (for 3-MeQ) assigned, inter alia, to the N-centered radicals on a pyrazin-2-one ring. The rate constants of the reactions of •OH with Q and 3-MeQ were found to be in the interval (5.9-9.7) × 109 M-1·s-1 and were assigned to their addition to benzene and pyrazin-2-one rings and H-abstraction from the pyrazin-2-one nitrogen. In turn, the transient absorption spectrum observed in the reaction of •N3 exhibits an absorption band with λmax = 350 nm. This absorption was assigned to the N-centered radical on the Pyr ring formed after deprotonation of the respective radical cation resulting from one-electron oxidation of 3-MeQ. The rate constant of the reaction of •N3 with 3 MeQ was found to be (6.0 ± 0.5) × 109 M-1·s-1. Oxidation of 3-MeQ by •N3 and Pyr by •OH and •N3 confirms earlier spectral assignments. With the rate constant of the •OH radical with Pyr (k = 9.2 ± 0.2) × 109 M-1·s‒1, a primary distribution of the •OH attack was estimated nearly equal between benzene and pyrazin-2-one rings.

Pharmacological Profile of Quinoxalinone

Quinoxalinone and its derivatives are used in organic synthesis for building natural and designed synthetic compounds and they have been frequently utilized as suitable skeletons for the design of biologically active compound. This review covers updated information on the most active quinoxalinone derivatives that have been reported to show considerable pharmacological actions such as antimicrobial, anti-inflammatory, antidiabetic, antiviral, antitumor, and antitubercular activity. It can act as an important tool for chemists to develop newer quinoxalinone derivatives that may prove to be better agents in terms of efficacy and safety.

5-Chlorothiophene-2-carboxylic acid [(S)-2-[2-methyl-3-(2-oxopyrrolidin-1-yl)benzenesulfonylamino]-3-(4-methylpiperazin-1-yl)-3-oxopropyl]amide (SAR107375), a selective and potent orally active dual thrombin and factor Xa inhibitor

Compound 15 (SAR107375), a novel potent dual thrombin and factor Xa inhibitor resulted from a rational optimization process. Starting from compound 14, with low factor Xa and modest anti-thrombin inhibitory activities (IC50's of 3.5 and 0.39 μM, respectively), both activities were considerably improved, notably through the incorporation of a neutral chlorothiophene P1 fragment and tuning of P2 and P3-P4 fragments. Final optimization of metabolic stability with microsomes led to the identification of 15, which displays strong activity in vitro vs factor Xa and thrombin (with Ki's of 1 and 8 nM, respectively). In addition 15 presents good selectivity versus related serine proteases (roughly 300-fold), including trypsin (1000-fold), and is very active (0.39 μM) in the thrombin generation time (TGT) coagulation assay in human platelet rich plasma (PRP). Potent in vivo activity in a rat model of venous thrombosis following iv and, more importantly, po administration was also observed (ED50 of 0.07 and 2.8 mg/kg, respectively). Bleeding liability was reduced in the rat wire coil model, more relevant to arterial thrombosis, with 15 (blood loss increase of 2-fold relative to the ED80 value) compared to rivaroxaban 2 and dabigatran etexilate 1a.

Concise route to a series of novel 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones

This report presents a novel three step solution phase protocol to synthesize 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones. The strategy utilizes ethyl glyoxalate and mono-N-Boc-protected-o-phenylenediamine derivatives in the Ugi-Azide multi-component reaction (MCR) to generate a unique 1,5-disubstituted tetrazole. Subsequent acid treatment stimulates a simultaneous Boc deprotection and intramolecular cyclization leading to bis-3,4-dihydroquinoxalinone tetrazoles. Direct oxidation using a stable solid-phase radical catalyst (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) with ceric ammonium nitrate (CAN) in catalytic fashion initiating aerobic oxidation, completes the entire procedure to generate a series of original unique bis-quinoxalinone tetrazoles. The method was also expanded to produce a bis-benzodiazepine tetrazole.

A novel route to synthesize libraries of quinoxalines via Petasis methodology in two synthetic operations

This communication reveals an innovative and facile procedure to prepare quinoxalines in two synthetic steps. The microwave assisted Petasis reaction is followed by the acid mediated unmasking of an internal amino nucleophile, cyclodehydration and oxidation to give collections of quinoxalines in good to excellent yields.

Exploring QSARs for inhibitory effect of a set of heterocyclic thrombin inhibitors by multilinear regression refined by artificial neural network and molecular docking simulations

Several non-peptide heterocyclic compounds reported as potent thrombin inhibitors in vitro were chosen to carry out a QSAR study upon them using MLR and ANN analysis. In order to identify the best QSAR models, the input for ANN consisted of those subsets of descriptors used in the MLR models. The best QSAR models contained the SIC₀ descriptor as the main topological descriptor. To identify the physical and chemical properties involved in the ligand-thrombin complexes, an automated ligand-flexible docking procedure was used. The docking results suggest that the thrombin inhibition by these heterocyclic compounds is driven by π-π, hydrogen bonds and salt bridge interactions. The best Gibbs free energy of ligand binding was found at the thrombin sites S1 and D. We have shown that it is possible to build MLR models with geometries taken from two different sources (semi-empirical and MD geometries) and obtain similar results.

Enantioselective synthesis of benzimidazolyl quinoxalinones on soluble polymer support using focused microwave irradiation

Focused microwave irradiation has been applied to a multistep synthetic sequence of reactions designed to generate benzimidazolyl quinoxalinones using a soluble polymer support. They were obtained by the ipso-fluoro (S(N)Ar) displacement of the immobilized ortho-nitro fluoro benzimidazoles with chiral alpha amino esters under microwave irradiation. Intermediate chiral organic-polymer conjugates when subjected to neutral reduction underwent a spontaneous intramolecular ring closure. Cleavage of the polymer support, at room temperature, did not cause any significant racemization resulting in the generation of a chiral molecular library with two points of structural diversity.

Prodrug-based design, synthesis, and biological evaluation of N-benzenesulfonylpiperidine derivatives as novel, orally active factor Xa inhibitors

We describe here our investigation of a new series of orally active fXa inhibitors based on a prodrug strategy. Solid-phase parallel synthesis identified a unique series of fXa inhibitors with a substituted benzenesulfonyl group as a novel S4 binding element. This series resulted in compound 39, which exhibited potent inhibitory activity against fXa (IC50 = 13 nM) and excellent selectivity over thrombin (>7000-fold). The masking of its highly hydrophilic groups led to the creation of related prodrug 28, which demonstrated an anticoagulant effect after oral dosing.