N-Methylanilide and N-methylbenzamide derivatives as phosphodiesterase 10A (PDE10A) inhibitors

Medicinal chemistry strategies for the development of phosphodiesterase 10A (PDE10A) inhibitors - An update of recent progress

Phosphodiesterase 10A is a member of Phosphodiesterase (PDE)-superfamily of the enzyme which is responsible for hydrolysis of cAMP and cGMP to their inactive forms 5'-AMP and 5'-GMP, respectively. PDE10A is highly expressed in the brain, particularly in the putamen and caudate nucleus. PDE10A plays an important role in the regulation of localization, duration, and amplitude of the cyclic nucleotide signalling within the subcellular domain of these regions, and thereby modulation of PDE10A enzyme can give rise to a new therapeutic approach in the treatment of schizophrenia and other neurodegenerative disorders. Limitation of the conventional therapy of schizophrenia forced the pharmaceutical industry to move their efforts to develop a novel treatment approach with reduced side effects. In the past decade, considerable developments have been made in pursuit of PDE10A centric antipsychotic agents by several pharmaceutical industries due to the distribution of PDE10A in the brain and the ability of PDE10A inhibitors to mimic the effect of D2 antagonists and D1 agonists. However, no selective PDE10A inhibitor is currently available in the market for the treatment of schizophrenia. The present compilation concisely describes the role of PDE10A inhibitors in the therapy of neurodegenerative disorders mainly in psychosis, the structure of PDE10A enzyme, key interaction of different PDE10A inhibitors with human PDE10A enzyme and recent medicinal chemistry developments in designing of safe and effective PDE10A inhibitors for the treatment of schizophrenia. The present compilation also provides useful information and future direction to bring further improvements in the discovery of PDE10A inhibitors.

K2S2O8-Mediated Hydroxyalkylation of Benzothiazoles with Alcohols in Aqueous Solution

The K2S2O8-mediated hydroxyalkylation of 2H-benzothiazoles with aliphatic alcohols in aqueous solution was described. The mild and convenient protocol generated a series of hydroxyalkylated benzothiazoles in moderate to good yields. Besides, benzimidazole and ethers were also compatible in this reaction, leading to corresponding C2 ether-substituted heteroarenes.

Efficient synthesis of 2-substituted azoles: radical C–H alkylation of azoles with dicumyl peroxide, methylarenes and cycloalkanes under metal-free condition

A simple and efficient synthesis of 2-substituted azoles by alkylation of azoles with dicumyl peroxide, methylarenes and cycloalkanes under metal-free condition has been developed.

Silver-catalyzed C2-selective direct alkylation of heteroarenes with tertiary cycloalkanols

A silver-catalyzed regioselective C2-alkylation of heteroarenes with primary radicals produced by tertiary cycloalkanols was developed.

Fragment-assisted hit investigation involving integrated HTS and fragment screening: Application to the identification of phosphodiesterase 10A (PDE10A) inhibitors

Fragment-based drug design (FBDD) relies on direct elaboration of fragment hits and typically requires high resolution structural information to guide optimization. In fragment-assisted drug discovery (FADD), fragments provide information to guide selection and design but do not serve as starting points for elaboration. We describe FADD and high-throughput screening (HTS) campaign strategies conducted in parallel against PDE10A where fragment hit co-crystallography was not available. The fragment screen led to prioritized fragment hits (IC50's ∼500μM), which were used to generate a hypothetical core scaffold. Application of this scaffold as a filter to HTS output afforded a 4μM hit, which, after preparation of a small number of analogs, was elaborated into a 16nM lead. This approach highlights the strength of FADD, as fragment methods were applied despite the absence of co-crystallographical information to efficiently identify a lead compound for further optimization.

Synthesis and in vivo evaluation of novel quinoline derivatives as phosphodiesterase 10A inhibitors

A novel class of phosphodiesterase 10A (PDE10A) inhibitors with improved metabolic stability in mouse liver microsomes were designed and synthesized starting from 2-({4-[1-methyl-4-(pyridin-4-yl)-1H-pyrazol-3-yl]phenoxy}methyl)quinoline (MP-10). Replacement of the phenoxymethyl part of MP-10 with an oxymethyl phenyl unit led to the identification of 2-[4-({[1-methyl-4-(pyridin-4-yl)-1H-pyrazol-3-yl]oxy}methyl)phenyl]quinoline (14), which showed moderate PDE10A inhibitory activity with improved metabolic stability in mouse and human liver microsomes over MP-10. Compound 14 showed high concentrations in plasma and brain after intraperitoneal administration and dose-dependently attenuated the hyperlocomotion induced by phencyclidine in mice, and oral administration of 14 (0.1, 0.3 mg/kg) also improved visual-recognition memory impairment in mice.

Insights into the impact of N- and O-methylation on aqueous solubility and lipophilicity using matched molecular pair analysis

The impact of N- and O-methylation on aqueous solubility and measured lipophilicity for several chemically diverse structural classes is described.