Quinoxaline-2,3-diones: potential d-amino acid oxidase (DAAO) inhibitors

Discovery of FXR/PPARγ dual partial agonist

Farnesoid X receptor (FXR) and peroxisome proliferator-activated receptor (PPAR)γ are nuclear receptor 1 superfamily of transcription factors. FXR and PPARγ agonists have been individually investigated in clinical trial of anti-diabetic agents in the patients with nonalcoholic fatty liver disease (NAFLD). Regarding recent agonist development, the partial agonists for FXR and PPARγ are drawing attention from the standpoint of avoiding overactive responses caused by full agonists. In this article, we report that 18 with a benzimidazole scaffold possesses FXR/PPARγ dual partial agonistic activity. In addition, 18 shares the ability to reduce cyclin-dependent kinase 5-mediated phosphorylation of PPARγ-Ser273 and the metabolic stability in mouse liver microsome assay. To date, there are no published reports on FXR/PPARγ dual partial agonists with biological profiles similar to 18. Thus, the analog would be a feasible candidate as an unprecedented approach to NAFLD associated with type 2 diabetes mellitus.

New quinoxaline compounds as DPP-4 inhibitors and hypoglycemics: design, synthesis, computational and bio-distribution studies

The current work represents the design and synthetic approaches of a new set of compounds 6–10 bearing the 1,4-dimethyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide scaffold. The biological evaluation revealed that most of the new compounds were promising selective dipeptidyl peptidase-IV (DPP-4) inhibitors and in vivo hypoglycemic agents utilizing linagliptin as a standard drug. The acute toxicity examination confirmed the safety profile of all compounds. Molecular docking studies related the significant DPP-4 suppression activity of compounds 9a, 10a, 10f, 10g to their nice fitting in the active pocket of DPP-4. In addition, the molecular dynamic study exhibited the stability of both 10a and 10g within the active site of DPP-4. The QSAR study showed that the difference between the predicted activities is very close to the experimental suppression effect. Moreover, both compounds 10a and 10g obeyed Lipinski's rule, indicating their efficient oral bioavailability. Compound 10a was radiolabeled, forming the ¹³¹I-SQ compound 10a to study the pharmacokinetic profile of this set of compounds. The biodistribution pattern hit the target protein since the tracer accumulated mainly in the visceral organs where DPP-4 is secreted in a high-level, thus with consequent stimulation of insulin secretion, leading to the target hypoglycemic effect.

The current work represents the design and synthetic approaches of a new set of compounds 6–10 bearing the 1,4-dimethyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide scaffold.

Overcoming imatinib resistance in chronic myelogenous leukemia cells using non-cytotoxic cell death modulators

Recent studies examined the possibility to overcome imatinib resistance in chronic myeloid leukemia (CML) patients by combination therapy with peroxisome proliferator-activated receptor gamma (PPARγ) ligands. Pioglitazone, a full PPARγ agonist, improved the survival of patients by the gradual elimination of the residual CML stem cell pool. To evaluate the importance of the pharmacological profile of PPARγ agonists on the ability to circumvent resistance, the partial PPARγ agonist 4'-((2-propyl-1H-benzo[d]imidazol-1-yl)methyl)-[1,1'-biphenyl]-2-carboxylic acid, derived from telmisartan, and other related derivatives were investigated. The 4-substituted benzimidazole derivatives bearing a [1,1'-biphenyl]-2-carboxamide moiety sensitized K562-resistant cells to imatinib treatment. Especially the derivatives 18a-f, which did not activate PPARγ to more than 40% at 10 μM, retrieved the cytotoxicity of imatinib in these cells. The cell death modulating properties were higher than that of pioglitazone. It is of interest to note that all novel compounds were not cytotoxic neither on non-resistant nor on resistant cells. They exerted antitumor potency only in combination with imatinib.

Quinoxalinedione deprotonation is important for glutamate receptor binding

Quinoxalinediones are an important class of competitive antagonists at ionotropic glutamate receptors (iGluRs), where they are widely used to block α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptor responses. In this study we utilize two prototypic quinoxalinedione antagonists, namely DNQX and CNQX, which quench the intrinsic fluorescence of the ligand binding domain (LBD), to perform in vitro binding assays. We find that binding of DNQX and CNQX at the AMPA receptor GluA2 LBD is strongly pH dependent, whereas glutamate binding is not affected by pH. We also show that the deprotonation of DNQX, CNQX and other quinoxalinediones (NBQX and YM90K) occurs close to physiological pH, which can be explained by the lactam-lactim tautomerization of the quinoxalinedione scaffold. Analysis of our binding data indicates that quinoxalinedione deprotonation is a key requirement for binding, as we find a >100-fold higher affinity for binding of the monoanionic form compared to the neutral form. This suggests a large electrostatic contribution to the interaction with a conserved arginine residue located in the binding pocket of iGluRs. The strong pH dependence of quinoxalinedione binding, which has not previously been reported, is relevant for structure-function studies, but also for the use of quinoxalinediones in physiological experiments and envisioned therapeutic applications.

Semi-synthesis, structural modification and biological evaluation of 5-arylbenzofuran neolignans

5-Arylbenzofuran neolignans, a newfound class of natural products, were semi-synthesized, and a series of derivatives were designed, synthesized and evaluated for cytotoxicity.

Route to Benzimidazol-2-ones via Decarbonylative Ring Contraction of Quinoxalinediones: Application to the Synthesis of Flibanserin, A Drug for Treating Hypoactive Sexual Desire Disorder in Women and Marine Natural Product Hunanamycin Analogue

A simple and practical method to access a variety of benzimidazol-2-ones is reported here. A series of N-alkyl-substituted benzimidazol-2-ones were synthesized by decarbonylative ring contraction starting from corresponding quinoxalinediones for the first time. The utility of the method has been demonstrated by synthesizing recently approved controversial drug flibanserin (Addyi) and a urea analogue of marine antibiotic natural product hunanamycin-A.