Novel adenosine A(2A) receptor ligands: a synthetic, functional and computational investigation of selected literature adenosine A(2A) receptor antagonists for extending into extracellular space.

Growing evidence has suggested a role in targeting the adenosine A2A receptor for the treatment of Parkinson's disease. The literature compounds KW 6002 (2) and ZM 241385 (5) were used as a starting point from which a series of novel ligands targeting the adenosine A2A receptor were synthesized and tested in a recombinant human adenosine A2A receptor functional assay. In order to further explore these molecules, we investigated the biological effects of assorted linkers attached to different positions on selected adenosine A2A receptor antagonists, and assessed their potential binding modes using molecular docking studies. The results suggest that linking from the phenolic oxygen of selected adenosine A2A receptor antagonists is relatively well tolerated due to the extension towards extracellular space, and leads to the potential of attaching further functionality from this position.

A novel series of benzimidazole NR2B-selective NMDA receptor antagonists.

A series of novel benzimidazoles are discussed as NR2B-selective N-methyl-d-aspartate (NMDA) receptor antagonists. High throughput screening (HTS) efforts identified a number of potent and selective NR2B antagonists such as 1. Exploration of the substituents around the core of this template identified a number of compounds with high potency for NR2B (pIC(50) >7) and good selectivity against the NR2A subunit (pIC(50) <4.3) as defined by FLIPR-Ca(2+) and radioligand binding studies. These agents offer potential for the development of therapeutics for a range of nervous system disorders including chronic pain, neurodegeneration, migraine and major depression.

5-HT6 receptor antagonists: prospects for the treatment of cognitive disorders including dementia.

Several serious neurological and psychiatric disorders are associated with cognitive impairment. Thus, drugs targeting the cognitive symptoms of these diseases would be expected to provide significant benefits to these patient populations. A growing body of preclinical evidence has supported the use of serotonin 5-HT6 receptor antagonism as a promising mechanism for treating cognitive dysfunction. Following the discovery of a new generation of 5-HT6 receptor ligands with improved physicochemical properties, leading to superior brain penetration, additional support for the 5-HT6 hypothesis has been provided by clinical trial data for three molecules in drug development.

Intramolecular palladium-catalyzed direct arylation of alkenyl triflates.

A catalyst generated from Pd(OAc)2 and dppp is effective for the direct intramolecular arylation of alkenyl triflates. Conjugated alkene-arene-containing carbocycles are produced in good yield. The process tolerates a variety of aryl substituents as well a simple heteroaryl groups. Electron-deficient aryl rings deliver faster reactions.

Synthesis and pharmacological evaluation of dual acting ligands targeting the adenosine A2A and dopamine D2 receptors for the potential treatment of Parkinson's disease.

A relatively new strategy in drug discovery is the development of dual acting ligands. These molecules are potentially able to interact at two orthosteric binding sites of a heterodimer simultaneously, possibly resulting in enhanced subtype selectivity, higher affinity, enhanced or modified physiological response, and reduced reliance on multiple drug administration regimens. In this study, we have successfully synthesized a series of classical heterobivalent ligands as well as a series of more integrated and "drug-like" dual acting molecules, incorporating ropinirole as a dopamine D2 receptor agonist and ZM 241385 as an adenosine A2A receptor antagonist. The best compounds of our series maintained the potency of the original pharmacophores at both receptors (adenosine A2A and dopamine D2). In addition, the integrated dual acting ligands also showed promising results in preliminary blood-brain barrier permeability tests, whereas the classical heterobivalent ligands are potentially more suited as pharmacological tools.

Discovery of GSK2795039, a Novel Small Molecule NADPH Oxidase 2 Inhibitor.

AIMS: The NADPH oxidase (NOX) family of enzymes catalyzes the formation of reactive oxygen species (ROS). NOX enzymes not only have a key role in a variety of physiological processes but also contribute to oxidative stress in certain disease states. To date, while numerous small molecule inhibitors have been reported (in particular for NOX2), none have demonstrated inhibitory activity in vivo. As such, there is a need for the identification of improved NOX inhibitors to enable further evaluation of the biological functions of NOX enzymes in vivo as well as the therapeutic potential of NOX inhibition. In this study, both the in vitro and in vivo pharmacological profiles of GSK2795039, a novel NOX2 inhibitor, were characterized in comparison with other published NOX inhibitors. RESULTS: GSK2795039 inhibited both the formation of ROS and the utilization of the enzyme substrates, NADPH and oxygen, in a variety of semirecombinant cell-free and cell-based NOX2 assays. It inhibited NOX2 in an NADPH competitive manner and was selective over other NOX isoforms, xanthine oxidase, and endothelial nitric oxide synthase enzymes. Following systemic administration in mice, GSK2795039 abolished the production of ROS by activated NOX2 enzyme in a paw inflammation model. Furthermore, GSK2795039 showed activity in a murine model of acute pancreatitis, reducing the levels of serum amylase triggered by systemic injection of cerulein. INNOVATION AND CONCLUSIONS: GSK2795039 is a novel NOX2 inhibitor that is the first small molecule to demonstrate inhibition of the NOX2 enzyme in vivo.

Tandem cobalt mediated rearrangement and Pauson-Khand reaction for the synthesis of functionalized polycyclic systems.

The cobalt mediated rearrangement of enol ether complex 2 furnishes cyclic ketone 6, which undergoes an intramolecular Pauson-Khand reaction allowing access to functionalized polycyclic systems.

Procognitive 5-HT6 antagonists in the rat forced swimming test: potential therapeutic utility in mood disorders associated with Alzheimer's disease.

AIMS: 5-HT(6) receptor subtype is predominantly expressed in the brain, and preclinical evidence suggests its potential role in the cognitive function. Brain microdialysis studies demonstrated that 5-HT(6) antagonists enhance not only cholinergic but also monoaminergic neurotransmission, a property that may differentiate from acetylcholine esterase (AChE) inhibitors such as donepezil. In this study we compared the antidepressant-like effects of 5-HT(6) antagonists with donepezil to determine whether their different effects on monoamines are behaviorally relevant. MAIN METHODS: Selective 5-HT(6) antagonists (SB-399885 and SB-271046) and donepezil were evaluated in the rat forced swimming test since this is known to identify drugs such as antidepressants which can increase brain monoamine levels. Binding assay was undertaken by using [(125)I]SB-258585 to measure brain 5-HT(6) receptor occupancy. KEY FINDINGS: Systemic administration of SB-399885 (3 and 10 mg/kg, i.p.) and SB-271046 (10 and 30 mg/kg, i.p.) produced a significant reduction of immobility time in the rat forced swimming test with a similar profile in terms of 5-HT(6) receptor occupancy (62 and 96% for 3 and 10 mg/kg SB-399885 respectively; 56 and 84% for 10 and 30 mg/kg SB-271046 respectively). In contrast, donepezil (0.5 and 1 mg/kg i.p.) did not show any effects in this model. SIGNIFICANCE: These data suggest that 5-HT(6) antagonists, at doses corresponding to those occupy central 5-HT(6) receptors, could have an antidepressive effect in humans. This may differentiate 5-HT(6) antagonists from AChE inhibitors with respect to the mood control in the symptomatic treatment of Alzheimer's disease.

2,5-Diketopiperazines as potent and selective oxytocin antagonists 1: Identification, stereochemistry and initial SAR.

This paper covers efforts to discover orally active potent and selective oxytocin antagonists. Screening pooled libraries identified a novel series of 2,5-diketopiperazine derivatives with antagonist activity at the human oxytocin receptor. We report the initial structure-activity relationship investigations and the determination of the stereochemistry of the most potent compounds.

Investigation of a stereoselective co-mediated rearrangement reaction.

A stereocontrolled approach to alpha-alkyl beta-alkynyl cyclohexanones is reported through a Lewis acid mediated rearrangement reaction of enol ethers bearing an Co-alkyne moiety. The reaction proceeds with high levels of stereoselectivity in the presence of Ti- and B-Lewis acids to provide a range of alpha,beta-disubstituted cyclohexanones in high yield although the products are prone to epimerization at the alpha-position in the presence of the B-promoter system. The potential for an enantioselective variant of this process is outlined, and a rationale for the observed stereochemical trends and detailed structural analyses of the ketone products are described.