Alpha,alpha-difluoro-beta-ketophosphonates as potent inhibitors of protein tyrosine phosphatase 1B

Recent trends in the direct oxyphosphorylation of C-C multiple bonds

Due to the wide importance of β-phosphorylated ketones as key building-blocks in the fabrication of various pharmaceutically active organophosphorus compounds, finding new and truly efficient methods for their preparation from simple, low-cost and ubiquitous feedstock materials within a single click is an interesting subject in organic synthesis. Recently, oxyfunctionalization of carbon-carbon multiple bonds has arisen as a straightforward and versatile tool for the synthesis of complex organic molecules from the simple and easily accessible alkenes/alkynes via a single operation. In this context, oxyphosphorylation of alkenes/alkynes with P(O)-H compounds has attracted considerable attention as a unique procedure for the construction of β-phosphorylated ketones. In this review, we outline the recent advances and developments in this fast-growing research field with particular emphasis on the mechanistic aspects of reaction.

Study of triaryl-based sulfamic acid derivatives as HPTPβ inhibitors

A series of novel triaryl-based sulfamic acid analogs was designed, synthesized and evaluated as inhibitors of human protein tyrosine phosphatase beta (HPTPβ). A novel, easy and efficient synthetic method was developed for target compounds, and the activity determination results showed that most of compounds were good HPTPβ inhibitors. Interestingly, the compounds G4 and G25 with simple structure not only showed potent inhibitory activity on HPTPβ but also had good inhibitory selectivity over other PTPs (PTP1B, SHP2, LAR and TC-PTP). The molecular docking simulation of compounds with the protein HPTPβ helped us understand the structure-activity relationship and clarify some confusing assay results. This research provides references for further drug design of HPTPβ and other PTPs inhibitors.

Aldose reductase and protein tyrosine phosphatase 1B inhibitors as a promising therapeutic approach for diabetes mellitus

Diabetes mellitus is a metabolic disease characterized by high blood glucose levels and usually associated with several chronic pathologies. Aldose reductase and protein tyrosine phosphatase 1B enzymes have identified as two novel molecular targets associated with the onset and progression of type II diabetes and related comorbidities. Although many inhibitors against these enzymes have already found in the field of diabetic mellitus, the research for discovering more effective and selective agents with optimal pharmacokinetic properties continues. In addition, dual inhibition of these target proteins has proved as a promising therapeutic approach. A variety of diverse scaffolds are presented in this review for the future design of potent and selective inhibitors of aldose reductase and protein tyrosine phosphatase 1B based on the most important structural features of both enzymes. The discovery of novel dual aldose reductase and protein tyrosine phosphatase 1B inhibitors could be effective therapeutic molecules for the treatment of insulin-resistant type II diabetes mellitus. The methods used comprise a literature survey and X-ray crystal structures derived from Protein Databank (PDB). Despite the available therapeutic options for type II diabetes mellitus, the inhibitors of aldose reductase and protein tyrosine phosphatase 1B could be two promising approaches for the effective treatment of hyperglycemia and diabetes-associated pathologies. Due to the poor pharmacokinetic profile and low in vivo efficacy of existing inhibitors of both targets, the research turned to more selective and cell-permeable agents as well as multi-target molecules.

Phosphotyrosine isosteres: past, present and future

Tyrosine phosphorylation is a critical component of signal transduction for multicellular organisms, particularly for pathways that regulate cell proliferation and differentiation. While tyrosine kinase inhibitors have become FDA-approved drugs, inhibitors of the other important components of these signaling pathways have been harder to develop. Specifically, direct phosphotyrosine (pTyr) isosteres have been aggressively pursued as inhibitors of Src homology 2 (SH2) domains and protein tyrosine phosphatases (PTPs). Medicinal chemists have produced many classes of peptide and small molecule inhibitors that mimic pTyr. However, balancing affinity with selectivity and cell penetration has made this an extremely difficult space for developing successful clinical candidates. This review will provide a comprehensive picture of the field of pTyr isosteres, from early beginnings to the current state and trajectory. We will also highlight the major protein targets of these medicinal chemistry efforts, the major classes of peptide and small molecule inhibitors that have been developed, and the handful of compounds which have been tested in clinical trials.

Design and synthesis of new potent PTP1B inhibitors with the skeleton of 2-substituted imino-3-substituted-5-heteroarylidene-1,3-thiazolidine-4-one: Part I

A new series of 2-substituted imino-3-substituted-5- heteroarylidene-1,3-thiazolidine-4-ones as the potent bidentate PTP1B inhibitors were designed and synthesized in this paper. All of the new compounds were characterized and identified by spectra analysis. The biological screening test against PTP1B showed that some of these compounds have the positive inhibitory activity against PTP1B. The activity of the compounds with 5-substituted pyrrole on 5-postion of 1,3-thiazolidine-4-one are more potent than that of those compounds with 5-substituted pyridine group. Compound 14b, 14h and 14i showed IC50 values of 8.66 μM, 6.83 μM and 6.09 μM against PTP1B, respectively. Docking analysis of these active compounds with PTP1B showed the possible interaction modes of these biheterocyclic compounds with the active sites of PTP1B. The inhibition tests against oncogenetic CDC25B were also conducted on this set of compounds to evaluate the selectivity and possible anti-neoplastic activity. Compound 14b also showed the lowest IC50 of 1.66 μM against CDC25B among all the possible inhibitors, including 14g, 14h, 14i and 15c. Some pharmacological parameters including VolSurf, steric and electric descriptors of all the compounds were calculated to give some hints about the relative relationship with the biological activity. The result of this study might give some light on designing the possible anti-cancer drugs targeting at phosphatases. The most active compound 14i might be used as the lead compound for further structure modification of the new low molecular weight PTP1B inhibitors with the N-containing heterocyclic skeleton.

Phosphonate derivatives of tetraazamacrocycles as new inhibitors of protein tyrosine phosphatases

α,α-Difluoro-β-ketophosphonate derivatives of tetraazamacrocycles were synthesized and found to be potential inhibitors of protein tyrosine phosphatases.

Mechanism of Oxidative Stress and Synapse Dysfunction in the Pathogenesis of Alzheimer's Disease: Understanding the Therapeutics Strategies

Synapses are formed by interneuronal connections that permit a neuronal cell to pass an electrical or chemical signal to another cell. This passage usually gets damaged or lost in most of the neurodegenerative diseases. It is widely believed that the synaptic dysfunction and synapse loss contribute to the cognitive deficits in patients with Alzheimer's disease (AD). Although pathological hallmarks of AD are senile plaques, neurofibrillary tangles, and neuronal degeneration which are associated with increased oxidative stress, synaptic loss is an early event in the pathogenesis of AD. The involvement of major kinases such as mitogen-activated protein kinase (MAPK), extracellular receptor kinase (ERK), calmodulin-dependent protein kinase (CaMKII), glycogen synthase-3β (GSK-3β), cAMP response element-binding protein (CREB), and calcineurin is dynamically associated with oxidative stress-mediated abnormal hyperphosphorylation of tau and suggests that alteration of these kinases could exclusively be involved in the pathogenesis of AD. N-methyl-D-aspartate (NMDA) receptor (NMDAR) activation and beta amyloid (Aβ) toxicity alter the synapse function, which is also associated with protein phosphatase (PP) inhibition and tau hyperphosphorylation (two main events of AD). However, the involvement of oxidative stress in synapse dysfunction is poorly understood. Oxidative stress and free radical generation in the brain along with excitotoxicity leads to neuronal cell death. It is inferred from several studies that excitotoxicity, free radical generation, and altered synaptic function encouraged by oxidative stress are associated with AD pathology. NMDARs maintain neuronal excitability, Ca(2+) influx, and memory formation through mechanisms of synaptic plasticity. Recently, we have reported the mechanism of the synapse redox stress associated with NMDARs altered expression. We suggest that oxidative stress mediated through NMDAR and their interaction with other molecules might be a driving force for tau hyperphosphorylation and synapse dysfunction. Thus, understanding the oxidative stress mechanism and degenerating synapses is crucial for the development of therapeutic strategies designed to prevent AD pathogenesis.

Bidentate inhibitors of protein tyrosine phosphatases

SIGNIFICANCE

Protein tyrosine phosphatases (PTPs) are important enzymes that are involved in the regulation of cellular signaling. Evidence accumulated over the years has indicated that PTPs present exciting opportunities for drug discovery against diseases such as diabetes, cancer, autoimmune diseases, and tuberculosis. However, the highly conserved and partially positive charge of the catalytic sites of PTPs is a major challenge in the development of potent and highly selective PTP inhibitors.

RECENT ADVANCES

Here, we examine the strategy of developing bidentate inhibitors for selective inhibition of PTPs. Bidentate inhibitors are small-molecular-weight compounds with the ability to bind to both the active site and a non-conserved secondary phosphate binding site. This secondary phosphate binding site was initially discovered in protein tyrosine phosphatase 1B (PTP1B), and, hence, most of the bidentate inhibitors reported in this review are PTP1B inhibitors.

CRITICAL ISSUES

Although bidentate inhibition is a good strategy for developing potent and selective inhibitors, the cell membrane permeability and pharmacokinetic properties of the inhibitors are also important for successful drug development. In this review, we will also summarize the various efforts made toward the development of phosphotyrosine (pTyr) mimetics for increasing cellular permeability.

FUTURE DIRECTIONS

Even though the secondary phosphate binding site was initially found in PTP1B, structural data have shown that a secondary binding site can also be found in other PTPs, albeit with varying degrees of accessibility. Along with improvements in pTyr mimetics, we believe that the future will see an increase in the number of orally bioavailable bidentate inhibitors against the various classes of PTPs.

Novel biphenyl compound, VMNS2e, ameliorates streptozotocin-induced diabetic nephropathy in rats

AIM

To study the effect of a new biphenyl synthetic compound showing interactions with the active site of protein tyrosine phosphatase 1B by docking and molecular dynamics, VMNS2e in streptozotocin-induced diabetic nephropathy in rats with various renal function parameters and renal ultrastructure.

METHODS

Streptozotocin (55 mg/kg)-induced diabetic rats were orally treated once daily with VMNS2e (30, 60, and 120 mg/kg) for 8 weeks. The body weight and blood glucose levels of the rats were recorded during the study period. After 8 weeks of treatment creatinine clearance, urinary protein, blood urea nitrogen, urinary albumin excretion rate, and insulin levels were measured. An ultrastructure study of the kidney tissue was performed and the glomerular basement membrane thickness was measured.

RESULTS

Eight weeks of VMNS2e treatment significantly reduced the fasting blood glucose level, attenuated elevating blood urea nitrogen levels, and reduced glomerular basement membrane thickness.

CONCLUSION

It is concluded that VMNS2e treatment at 30 and 60 mg/kg, when given for 8 weeks, partly ameliorated early diabetic nephropathy in diabetic rats.

Synthesis and Reactivity Studies of α,α-Difluoromethylphosphinates

The preparation and reactivity of some α,α-difluorophosphinates is investigated. Alkylation of H-phosphinates with LiHMDS and ClCF(2)H gives the corresponding α,α-difluorophosphinates in good yield. Deprotonation of these reagents with alkyllithium or LDA is then studied. Subtle electronic effects translate into significant differences in the deprotonation/alkylation of the two "Ciba-Geigy reagents" (EtO)(2)CRP(O)(OEt)H (R = H, Me). On the other hand, attempted methylation of difluoromethyl-octyl-phosphinic acid butyl ester resulted in the exclusive alkylation of the octyl chain. Finally, reaction with carbonyl compounds results in the formation of 1,1-difluoro-2-phosphinoyl compounds.

Nucleophilic difluoromethylation and difluoromethylenation of aldehydes and ketones using diethyl difluoromethylphosphonate

New methodology for difluoromethylation and difluoromethylenation of aldehydes and ketones based on nucleophilic fluorination using diethyl difluoromethylphosphonate (1) was developed.

5-Arylidene-2,4-thiazolidinediones as inhibitors of protein tyrosine phosphatases

4-(5-Arylidene-2,4-dioxothiazolidin-3-yl)methylbenzoic acids (2) were synthesized and evaluated in vitro as inhibitors of PTP1B and LMW-PTP, two protein tyrosine phosphatases (PTPs) which act as negative regulators of the metabolic and mitotic signalling of insulin. The synthesis of compounds 2 represents an example of utilizing phosphotyrosine-mimetics to identify effective low molecular weight nonphosphorus inhibitors of PTPs. Several thiazolidinediones 2 exhibited PTP1B inhibitory activity in the low micromolar range with moderate selectivity for human PTP1B and IF1 isoform of human LMW-PTP compared with other related PTPs.

Probing acid replacements of thiophene PTP1B inhibitors

The following account describes our systematic effort to replace one of the carboxylate groups of our diacid thiophene PTP1B inhibitors. Active hits were validated using enzymatic assays before pursuing efforts to improve the potency. Only when the C2 carboxylic acid was replaced with another ionizable functional group was reversible and competitive inhibition retained. Use of a tetrazole ring or 1,2,5-thiadiazolidine-3-one-1,1-dioxide as a carboxylate mimetic led to the discovery of two unique starting series that showed improved permeability (PAMPA) and potency of the order of 300nM. The SAR from these efforts underscores some of the major challenges in developing small molecule inhibitors for PTP1B.

PTP-1B inhibitors: Cyclopenta[d][1,2]-oxazine derivatives

A series of novel cyclopenta[d][1,2]-oxazine derivatives was prepared and evaluated for their inhibitory activity toward protein tyrosine phosphatase 1B (PTP-1B). Compound 6s was found to be an inhibitor of PTP-1B with nanomolar IC(50) value and high level of selectivity over other recombinant phosphatases.

Discovery and structure–activity relationships of novel sulfonamides as potent PTP1B inhibitors

A series of novel sulfonamides containing a single difluoromethylene-phosphonate group were discovered to be potent inhibitors of protein tyrosine phosphatase 1B. Structure-activity relationships around the scaffold were investigated, leading to the identification of compounds with IC50 or Ki values in the low nanomolar range. These sulfonamide-based inhibitors exhibit 100 and 30 times higher inhibitory activity than the corresponding tertiary amines and carboxamides, respectively.

Novel α,α-Difluorohomophthalimides via Copper-Catalyzed Tandom Cross-Coupling−Cyclization of 2-Halobenzamides with α,α-Difluoro Reformatskii Reagent

Novel alpha,alpha-difluorohomophthalimides 2 were prepared by reacting N-substituted 2-halobenzamides with the alpha,alpha-difluoro Reformatskii reagent BrZnCF2CO2Et (3) in the presence of CuBr at room temperature. The synthesis involves a CuBr-mediated cross-coupling of 3 with aryl iodides or activated aryl bromides, followed by a spontaneous cyclization of the ethyl 2-benzamido-alpha,alpha-difluoroacetate intermediates at room temperature. N-unsubstituted alpha,alpha-difluorohomophthalimides 2 (R' = H), bearing an acidic imide proton capable of acting as a carboxylic acid bioisostere, were also prepared by reacting 3 equiv of 3 with the parent 2-iodobenzamides. Other aryl iodides such as 3-iodo-imidazo[1,2-alpha]pyridine were also used for the tandem coupling-cyclization reaction.