An Isoform-Selective PTP1B Inhibitor Derived from Nitrogen-Atom Augmentation of Radicicol

Bifunctionality of dirhodium tetracarboxylates in metallaphotocatalysis

Metallaphotocatalysis has been recognized as a pivotal catalysis enabling new reactivities. Traditional metallaphotocatalysis often requires two or more separate catalysts and exhibits flaw in cost and substrate-tolerance, thus representing an await-to-solve issue in catalysis. We herein realize metallaphotocatalysis with a bifunctional dirhodium tetracarboxylate ([Rh2]) alone. The [Rh2] shows an photocatalytic activity of promoting singlet oxygen (1O2) oxidation. By harnessing its photocatalytic activity, the [Rh2] catalyzes a photochemical cascade reaction (PCR) via combination of carbenoid chemistry and 1O2 chemistry. The PCR is characterized by high atom-efficiency, excellent stereoselectivities, mild conditions, scalable synthesis, and pharmaceutically interesting products. DFT calculations-aided mechanistic study rationalizes the reaction pathway and interprets the origin of stereoselectivities of the PCR. The products show inhibitory activity against PTP1B, being promising in the treatment of type II diabetes and cancers. Overall, here we show the bifunctional [Rh2] merges Rh-carbenoid chemistry and 1O2 chemistry.

Selective Inhibition of PTP1B by New Anthraquinone Glycosides from Knoxia valerianoides

Protein tyrosine phosphatase 1B (PTP1B) is highly validated as a therapeutic target for type 2 diabetes. However, active site-directed PTP1B inhibitors generally suffer from poor selectivity and bioavailability. Inspired by the identification of a unique anthraquinone-coumarin hybrid from Knoxia valerianoides exhibiting good specificity for PTP1B over the highly homologous T-cell protein tyrosine phosphatase (TCPTP), further chemical investigation of this plant species led to the isolation of nine new anthraquinone glycosides (1-9) and two known ones (10 and 11). Structures were characterized by a combination of spectroscopic analyses and chemical methods. All compounds showed PTP1B inhibitory activities with IC₅₀ values ranging from 1.05 to 13.74 μM. Compounds 4 and 8 exhibited greater than 64-fold selectivity over TCPTP. Enzyme kinetic studies revealed that compounds 4 and 7 behaved as mixed-type inhibitors. Docking studies predicted similar binding modes of these compounds at the allosteric site positioned between helices α3 and α6.

Recent advances in the development of allosteric protein tyrosine phosphatase inhibitors for drug discovery

Protein tyrosine phosphatases (PTPs) superfamily catalyzes tyrosine de-phosphorylation which affects a myriad of cellular processes. Imbalance in signal pathways mediated by PTPs has been associated with development of many human diseases including cancer, metabolic, and immunological diseases. Several compelling evidence suggest that many members of PTP family are novel therapeutic targets. However, the clinical development of conventional PTP-based active-site inhibitors originally was hampered by the poor selectivity and pharmacokinetic properties. In this regard, PTPs has been widely dismissed as "undruggable." Nonetheless, allosteric modulation has become increasingly an influential and alternative approach that can be exploited for drug development against PTPs. Unlike active-site inhibitors, allosteric inhibitors exhibit a remarkable target-selectivity, drug-likeness, potency, and in vivo activity. Intriguingly, there has been a high interest in novel allosteric PTPs inhibitors within the last years. In this review, we focus on the recent advances of allosteric inhibitors that have been explored in drug discovery and have shown an excellent result in the development of PTPs-based therapeutics. A special emphasis is placed on the structure-activity relationship and molecular mechanistic studies illustrating applications in chemical biology and medicinal chemistry.

Discovery of 5-(3-bromo-2-(2,3-dibromo-4,5-dimethoxybenzyl)-4,5-dimethoxybenzylidene)thiazolidine-2,4-dione as a novel potent protein tyrosine phosphatase 1B inhibitor with antidiabetic properties

Protein tyrosine phosphatase 1B (PTP1B) is a well-validated target in therapeutic interventions for type 2 diabetes mellitus (T2DM), however, PTP1B inhibitors containing negatively charged nonhydrolyzable pTyr mimetics are difficult to convert to the corresponding in vivo efficacy owing to poor cell permeability and oral bioavailability. In this work, molecules bearing less acidic heterocycle 2,4-thiazolidinedione and hydantoin were designed, synthesized and evaluated for PTP1B inhibitory potency, selectivity and in vivo antidiabetic efficacy. Among them, compound 5a was identified as a potent PTP1B inhibitor (IC₅₀ = 0.86 μM) with 5-fold selectivity over the highly homologous TCPTP. Long-term oral administration of 5a at a dose of 50 mg/kg not only significantly reduced blood glucose levels, triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) levels but also ameliorated insulin sensitivity in diabetic BKS db mice. Moreover, 5a enhanced the insulin-stimulated phosphorylation of IRβ, IRS-1 and Akt in C2C12 myotubes. A histopathological evaluation of liver and pancreas demonstrated that 5a increased liver glycogen storage and improved islet architecture with more β-cells and fewer α-cells in diabetic mice. Thus, our work demonstrated that compound 5a could serve as a lead compound for the discovery of new antidiabetic drugs.

Kinetic Resolution of Propargylic Ethers via [2,3]-Wittig Rearrangement to Synthesize Chiral α-Hydroxyallenes

An efficient kinetic resolution of propargyloxy dicarbonyl compounds via asymmetric [2,3]-Wittig rearrangement was achieved by using a chiral N,N'-dioxide/Ni^II complex catalyst. Various chiral α-allenyl alcohols were obtained in high enantioselectivities under mild conditions. The utility of this method was readily demonstrated in the asymmetric synthesis of the chiral 2,5-dihydrofuran derivative.

Catalytic asymmetric synthesis of 2,5-dihydrofurans using synergistic bifunctional Ag catalysis

We report a bifunctional Ag catalyst promoted intramolecular capture of oxonium ylides with alkynes for the enantioselective synthesis of 2,5-dihydrofurans. This represents unprecedented synergistic catalysis of a bifunctional Ag catalyst. Mechanistic studies revealed that [(R)-3,5-DM-BINAP](AgSbF₆)₂ (9) is likely to be the active catalytic species and that the reaction involves second order kinetics with respect to 9, suggesting that two molecules of 9 are involved in the intramolecular trapping of a Ag-associated oxonium ylide with a Ag-activated alkyne. Based on our mechanistic hypothesis, we further optimized the reaction, rendering a facile approach to 2,5-dihydrofurans in good to excellent yields in a highly chemo- and enantioselective fashion.