Novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonists: synthesis and structure-activity relationships of 6-(1H-imidazol-1-yl)-7-nitro-2,3(1H,4H)-pyrido[2,3-b]pyrazinedione and related compounds

Functionalized quinoxalinones as privileged structures with broad-ranging pharmacological activities

Quinoxalinones are a class of heterocyclic compounds which attract extensive attention owing to their potential in the field of organic synthesis and medicinal chemistry. During the past few decades, many new synthetic strategies toward the functionalization of quinoxalinone based scaffolds have been witnessed. Regrettably, there are only a few reports on the pharmacological activities of quinoxalinone scaffolds from a medicinal chemistry perspective. Therefore, herein we intend to outline the applications of multifunctional quinoxalinones as privileged structures possessing various biological activities, including anticancer, neuroprotective, antibacterial, antiviral, antiparasitic, anti-inflammatory, antiallergic, anti-cardiovascular, anti-diabetes, antioxidation, etc. We hope that this review will facilitate the development of quinoxalinone derivatives in medicinal chemistry.

High-performance sono/nano-catalytic system: CTSN/Fe3O4-Cu nanocomposite, a promising heterogeneous catalyst for the synthesis of N-arylimidazoles

Herein, a promising heterogeneous nanoscale catalytic system constructed of chitosan (CTSN, as a polymeric basis), iron oxide nanoparticles (Fe3O4 NPs, as the magnetic agent), and copper oxide nanoparticles (CuO NPs, as the main catalytic active site) is presented. Firstly, a convenient synthetic route for preparation of this novel nanocatalyst (CTSN/Fe3O4-Cu) is presented. Further, the synergistic catalytic effect between the novel-designed catalyst and ultrasound waves (USW) in N-arylation coupling reactions of the imidazole derivatives (using various aryl halides) is precisely discussed. Concisely, high reaction yields (98%) have been obtained in short reaction time (10 min) through applying a partial amount (0.01 g) of this nanocatalyst. As the main reason for high catalytic activity of CTSN/Fe3O4-Cu, nanosized cluster-shaped morphology, which provides a wide surface active area, can be expressed. However, as the most distinguished properties of CTSN/Fe3O4-Cu catalytic system, high convenience in separation and excellent reusability could be mentioned. CTSN/Fe3O4-Cu nanocomposite can be easily recovered by using an external magnet and reused at least for eight times with no significant decline in the catalytic activity. Structural characterizations of this novel system have been done by various analytical methods and the obtained results have been well interpreted in the context.

Heterocycles as nonclassical bioisosteres of α-amino acids

Bioisosterism of α-amino acids is often accomplished by replacing the α-carboxylate with one of the many known carboxylic acid bioisosteres. However, bioisosterism of the whole α-amino acid moiety is accomplished with heterocyclic bioisosteres that often display an acidic function. In this Minireview, we summarized the reported heterocycles as nonclassical bioisosteres of α-amino acids, which include quinoxaline-2,4(1H)-dione, quinoxaline-2,3(1H)-dione and quinolin-2(1H)-one, azagrevellin and azepine-derived structures. The binding mode of the crystalized bioisosteres were compared with those of the crystalized α-amino acids that bind in the same domain, and where no data on the crystal structure were available, the displacement studies of known orthosteric ligands were used. The reported bioisosteres share the following essential structural features for mimicking α-amino acids: an aromatic ring system joined to a lactam ring system with an acidic feature next to the lactam carbonyl, where this acidic feature together with the lactam carbonyl can mimic the α-carboxylate, and the lactam nitrogen together with the aromatic ring system can mimic the α-ammonium. The majority of these heterocycles can be prepared from three common corresponding starting materials: the corresponding anilines, isatins or anthranilic esters. The data collected here show the potential of this class of bioisosteres in the design of glutamate receptor ligands and beyond.

Discovery of 5-substituted 2-amino-4-chloro-8-((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)-7,8-dihydropteridin-6(5H)-ones as potent and selective Hsp90 inhibitors

A new series of compounds, 5-substituted 2-amino-4-chloro-8-((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)-7,8-dihydropteridin-6(5H)-ones, have been designed and identified as potent and selective inhibitors of Hsp90. These compounds demonstrated nanomolar potency toward both Hsp90-regulated Her2 degradation and the growth of a panel of human tumor cell lines in cell-based assays. High selectivity of these compounds toward Hsp90 was evident given that they did not inhibit a panel of 34 kinases at 10microM. The structure-activity relationship (SAR) of this series is reported here.

Competitive AMPA receptor antagonists

Glutamic acid (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system (CNS) where it is involved in the physiological regulation of different processes. It has been well established that excessive endogenous Glu is associated with many acute and chronic neurodegenerative disorders such as cerebral ischaemia, epilepsy, amiotrophic lateral sclerosis, Parkinson's, and Alzheimer's disease. These data have consequently added great impetus to the research in this field. In fact, many Glu receptor antagonists acting at the N-methyl-D-aspartic acid (NMDA), 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA), and/or kainic acid (KA) receptors have been developed as research tools and potential therapeutic agents. Ligands showing competitive antagonistic action at the AMPA type of Glu receptors were first reported in 1988, and the systemically active 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo[f]quinoxaline (NBQX) was first shown to have useful therapeutic effects in animal models of neurological disease in 1990. Since then, the quinoxaline template has represented the backbone of various competitive AMPA receptor antagonists belonging to different classes which had been developed in order to increase potency, selectivity and water solubility, but also to prolong the "in vivo" action. Compounds that present better pharmacokinetic properties and less serious adverse effects with respect to the others previously developed are undergoing clinical evaluation. In the near future, the most important clinical application for the AMPA receptor antagonists will probably be as neuroprotectant in neurodegenerative diseases, such as epilepsy, for the treatment of patients not responding to current therapies. The present review reports the history of competitive AMPA receptor antagonists from 1988 up to today, providing a systematic coverage of both the open and patent literature.

Design and structure–activity relationship of heterocyclic analogs of 4-amino-3-benzimidazol-2-ylhydroquinolin-2-ones as inhibitors of receptor tyrosine kinases

Herein are described a series of novel heterocyclic analogs of the 4-amino-3-benzimidazol-2-ylhydroquinolin-2-one scaffold. These compounds are potent inhibitors of receptor tyrosine kinases and exhibit favorable pharmacokinetic profiles. The synthesis and SAR of these compounds are described.

Synthesis of 2-pyridone-fused 2,2′-bipyridine derivatives. An unexpectedly complex solid state structure of 3,6-dimethyl-9H-4,5,9-triazaphenanthren-10-one

2-Pyridone-fused 2,2'-bipyridine derivatives and were synthesised. X-Ray diffraction analysis of revealed a highly complex solid state structure with a disordered molecule imbedded in a channel structure formed by a centrosymmetric lattice of hexagonally packed, hydrogen bonded columns. The columns are assembled from three symmetry independent molecules. Dimerisation of the self-complementary cis-amide hydrogen bond motif is overridden by the fulfilment of the proton coordination ability of the phenanthroline nitrogens in accordance with Etter's rules of hydrogen bond priorities.

Heterocyclic bibenzimidazole derivatives as topoisomerase I inhibitors

A series of 2'-heterocyclic derivatives of 5-phenyl-2,5'-1H-bibenzimidazoles were evaluated for topoisomerase I poisoning activity and cytotoxicity. Topo I poisoning activity was associated with 2'-derivatives that possessed a hydrogen atom capable of hydrogen bond formation, suggesting that the interatomic distances between such hydrogen atoms and the heteroatoms on the adjacent benzimidazole influence activity.

Neuroprotective effect of a novel AMPA receptor antagonist, YM90K, in rat focal cerebral ischaemia

It has been reported that delayed treatment with alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor antagonists was able to more completely inhibit glutamate neurotoxicity than N-methyl-D-aspartate (NMDA) receptor antagonists. Therefore, we investigated the neuroprotective effect of YM90K, an AMPA receptor antagonist, on focal cerebral lesions induced by thrombotic middle cerebral artery (MCA) occlusion in rats, particularly in the early phase of the cerebral ischaemic lesions. The MCA was occluded by photochemical reaction between transmural green light and systemically administered Rose Bengal, which causes endothelial injury followed by platelet adhesion, aggregation and formation of a platelet and fibrin-rich thrombus at the site of photochemical reaction. The infarct size was measured at 24 and 72 h after the MCA occlusion by a histochemical technique. YM90K was administered at various doses as a continuous infusion for 4 h, beginning 0 to 3 h after the MCA occlusion. YM90K (10 and 20 mg/kg per h for 4 h continuous infusion), starting immediately after the MCA occlusion significantly (P < 0.05) reduced the infarct size at 24 h after MCA occlusion in a dose-dependent manner. Further, the agent showed the same efficacy at 72 h after. The inhibitory effect of YM90K (20 mg/kg per h) on the infarct size was the same when the drug was started immediately, 1, 2 and 3 h after MCA occlusion. In conclusion, the novel AMPA receptor antagonist YM90K was effective in the treatment of focal cerebral ischaemic lesions. Activation of AMPA receptor may play a key role in the development of cerebral infarct in the early phase of ischaemia in rats.