Discovery of 4-hydroxy-1,6-naphthyridine-3-carbonitrile derivatives as novel PDE10A inhibitors

Rapid Synthesis of Highly Substituted 1,6-Naphthyridines Via Heteroaryl Ditriflates

We report the discovery of a convenient and efficient method for the synthesis of highly substituted 1,6-naphthyridines. A tandem nitrile hydration/cyclization procedure was developed to access 1,6-naphthyridine-5,7-diones under mild conditions. Subsequently, we have found that ditriflation of these intermediates provides 1,6-naphthyridine-5,7-ditriflates which are bench-stable but highly reactive intermediates that can be engaged in one-pot difunctionalization reactions leading to diverse drug-like products in rapid fashion.

Microwave-assisted one-pot two-step imine formation-hetero-Diels-Alder-detosylation/aromatization sequence: direct access to dibenzo[b,h][1,6]naphthyridines

A microwave-assisted, copper-catalyzed, one-pot, two-step reaction is established to access functionalized [1,6]naphthyridines in high yields (up to 96%) starting from 2-(N-propargylamino)benzaldehydes and arylamines. This rapid and operationally simple sequential reaction allowed the construction of two new heterocyclic rings and three new (2 C-C and 1 C-N) bonds in a single synthetic operation. This reaction tolerated various electron-donating and electron-withdrawing substituents well and delivered the desired products in a shorter reaction time under microwave irradiation. This reaction proceeds through a sequential imine formation, intramolecular [4 + 2] hetero-Diels-Alder reaction, and air oxidation, followed by detosylation-aromatization steps.

Synthesis and Anticancer Properties of Functionalized 1,6-Naphthyridines

The burgeoning interest in synthesis and biological applications of 1,6-naphthyridines reflects the importance of 1,6-naphthyridines in the synthetic as well as medicinal chemistry fields. Specially, 1,6-naphthyridines are pharmacologically active, with variety of applications such as anticancer, anti-human immunodeficiency virus (HIV), anti-microbial, analgesic, anti-inflammatory and anti-oxidant activities. Although collective recent synthetic developments have paved a path to a wide range of functionalized 1,6-naphthyridines, a complete correlation of synthesis with biological activity remains elusive. The current review focuses on recent synthetic developments from the last decade and a thorough study of the anticancer activity of 1,6-naphthyridines on different cancer cell lines. Anticancer activity has been correlated to 1,6-naphthyridines using the literature on the structure-activity relationship (SAR) along with molecular modeling studies. Exceptionally, at the end of this review, the utility of 1,6-naphthyridines displaying activities other than anticancer has also been included as a glimmering extension.

Advances in Discovery of PDE10A Inhibitors for CNS-Related Disorders. Part 1: Overview of the Chemical and Biological Research

Phosphodiesterase 10A (PDE10A) is a double substrate enzyme that hydrolyzes second messenger molecules such as cyclic-3',5'-adenosine monophosphate (cAMP) and cyclic-3',5'-guanosine monophosphate (cGMP). Through this process, PDE10A controls intracellular signaling pathways in the mammalian brain and peripheral tissues. Pharmacological, biochemical, and anatomical data suggest that disorders in the second messenger system mediated by PDE10A may contribute to impairments in the central nervous system (CNS) function, including cognitive deficits as well as disturbances of behavior, emotion processing, and movement. This review provides a detailed description of PDE10A and the recent advances in the design of selective PDE10A inhibitors. The results of preclinical studies regarding the potential utility of PDE10A inhibitors for the treatment of CNS-related disorders, such as schizophrenia as well as Huntington's and Parkinson's diseases are also summarized.

The rational search for PDE10A inhibitors from Sophora flavescens roots using pharmacophore‑ and docking‑based virtual screening

Phosphodiesterase 10A (PDE10A) has been confirmed to be an important target for the treatment of central nervous system (CNS) disorders. The purpose of the present study was to identify PDE10A inhibitors from herbs used in traditional Chinese medicine. Pharmacophore and molecular docking techniques were used to virtually screen the chemical molecule database of Sophora flavescens, a well‑known Chinese herb that has been used for improving mental health and regulating the CNS. The pharmacophore model generated recognized the common functional groups of known PDE10A inhibitors. In addition, molecular docking was used to calculate the binding affinity of ligand‑PDE10A interactions and to investigate the possible binding pattern. Virtual screening based on the pharmacophore model and molecular docking was performed to identify potential PDE10A inhibitors from S. flavescens. The results demonstrated that nine hits from S. flavescens were potential PDE10A inhibitors, and their biological activity was further validated using literature mining. A total of two compounds were reported to inhibit cyclic adenosine monophosphate phosphodiesterase, and one protected against glutamate‑induced oxidative stress in the CNS. The remaining six compounds require further bioactivity validation. The results of the present study demonstrated that this method was a time‑ and cost‑saving strategy for the identification of bioactive compounds from traditional Chinese medicine.

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.

Selective inhibitors of phosphodiesterases: therapeutic promise for neurodegenerative disorders

PDE inhibitors: significant contributors to the treatment of neurodegenerative diseases.

Advances in targeting cyclic nucleotide phosphodiesterases

Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants.

Combinatorial synthesis of fused tetracyclic heterocycles containing [1,6]naphthyridine derivatives under catalyst free conditions

A three-component reaction between an aromatic aldehyde, an amine, and tert-butyl 2,4-dioxopiperidine-1-carboxylate in EtOH at refluxing temperature gave fused tetracyclic heterocycles in high yields. The amines include 1H-indazol-5-amine, 1H-indazol-6-amine, 1H-indol-5-amine, and 1H-benzo[d]imidazol-5-amine, giving 11-aryl-3H-indazolo[5,4-b][1,6] naphthyridine, 11-aryl-1H-indazolo[6,7-b][1,6]naphthyridine, 11-aryl-3H-indolo[5,4-b][1,6]naph-thyridine, and 11-aryl-3H-imidazo[4',5':3,4]benzo[1,2-b][1,6]naphthyridine derivatives, respectively.

On dihydroorotate dehydrogenases and their inhibitors and uses

Proper nucleosides availability is crucial for the proliferation of living entities (eukaryotic cells, parasites, bacteria, and virus). Accordingly, the uses of inhibitors of the de novo nucleosides biosynthetic pathways have been investigated in the past. In the following we have focused on dihydroorotate dehydrogenase (DHODH), the fourth enzyme in the de novo pyrimidine nucleosides biosynthetic pathway. We first described the different types of enzyme in terms of sequence, structure, and biochemistry, including the reported bioassays. In a second part, the series of inhibitors of this enzyme along with a description of their potential or actual uses were reviewed. These inhibitors are indeed used in medicine to treat autoimmune diseases such as rheumatoid arthritis or multiple sclerosis (leflunomide and teriflunomide) and have been investigated in treatments of cancer, virus, and parasite infections (i.e., malaria) as well as in crop science.

Future directions in phosphodiesterase drug discovery

Research on phosphodiesterases both in academic labs and in the pharmaceutical industry has remained steady over the past 35 years. Although there have been some clinical successes, they have been clustered around just a couple of PDE isoforms, and disproportionate to the huge investment put forth against what seem like very druggable targets. This review attempts to uncover the reasons for the lack of productivity in PDE drug discovery, and summarizes the current hot areas of research. In addition, new insights gathered about structure-function relationships are highlighted, in particular those relating to enzyme regulation. Lastly, novel strategies for targeting the activation or inactivation of selected PDEs are proposed that may allow for a more targeted approach for PDE modulation.