Structure-activity relationships of a series of pyrrolo[3,2-d]pyrimidine derivatives and related compounds as neuropeptide Y5 receptor antagonists

Unconventional Site Selectivity in Palladium-Catalyzed Cross-Couplings of Dichloroheteroarenes under Ligand-Controlled and Ligand-Free Systems

Halides adjacent to nitrogen are conventionally more reactive in Pd-catalyzed cross-couplings of dihalogenated N-heteroarenes. However, a very sterically hindered N-heterocyclic carbene ligand is shown to promote room-temperature cross-coupling at C4 of 2,4-dichloropyridines with high selectivity (∼10:1). This work represents the first highly selective method with a broad scope for C4-coupling of these substrates where selectivity is clearly under ligand control. Under the optimized conditions, diverse substituted 2,4-dichloropyridines and related compounds undergo cross-coupling to form C4-C_(sp2) and C4-C_(sp3) bonds using organoboron, -zinc, and -magnesium reagents. The synthetic utility of this method is highlighted in multistep syntheses that combine C4-selective cross-coupling with subsequent nucleophilic aromatic substitution reactions. The majority of the products herein (71%) have not been previously reported, emphasizing the ability of this methodology to open up underexplored chemical space. Remarkably, we find that ligand-free "Jeffery" conditions enhance the C4 selectivity of Suzuki coupling by an order of magnitude (>99:1). These ligand-free conditions enable the first C5-selective cross-couplings of 2,5-dichloropyridine and 2,5-dichloropyrimidine.

Charge Sensitive Optical Detection for Measurement of Small-Molecule Binding Kinetics

Charge sensitive optical detection (CSOD) technique is a label-free method for real-time measurement of molecular interactions. Traditional label-free optical detection techniques mostly measure the mass of a molecule, and they are less sensitive to small molecules. In contrast, CSOD detects the charge of a molecule, where the signal does not diminish with the size of the molecule, thus capable for studying small molecules. In addition, CSOD is compatible with the standard microplate platform, making it suitable for high-throughput screening of drug candidates. In CSOD, an optical fiber functionalized with the probe molecule is dipped into a well of a microplate where an alternate perpendicular electrical field is applied to the fiber, which drives the fiber into oscillation because of the presence of surface charge on the fiber. The binding of the target molecules changes the charge of the fiber, and thus the amplitude and phase of the oscillating fiber, which are precisely measured through tracking of the optical images of the fiber tip.

Azaindole synthesis through dual activation catalysis with N-heterocyclic carbenes

A convergent, transition-metal-free synthesis of 2-aryl-azaindoles has been developed. The interception of a reactive aza-ortho-azaquinone methide intermediate by an acyl anion equivalent generated through carbene catalysis provides high yields, a wide substrate scope, and the synthesis of previously inaccessible azaindoles.

Study of Small-Molecule-Membrane Protein Binding Kinetics with Nanodisc and Charge-Sensitive Optical Detection

Nanodisc technology provides membrane proteins with a nativelike lipid bilayer and much-needed solubility and enables in vitro quantification of membrane protein binding with ligands. However, it has been a challenge to measure interaction between small-molecule ligands and nanodisc-encapsulated membrane proteins, because the responses of traditional mass-based detection methods scale with the mass of the ligands. We have developed a charge-sensitive optical detection (CSOD) method for label-free measurement of the binding kinetics of low molecular mass ligands with nanodisc-encapsulated membrane proteins. This microplate-compatible method is sensitive to the charge instead of the mass of a ligand and is able to measure both large and small molecules in a potentially high-throughput format. Using CSOD, we measured the binding kinetics between peptide and small-molecule ligands and a nanodisc-encapsulated potassium ion channel protein, KcsA-Kv1.3. Both association and dissociation rate constants for these ligands are obtained for the first time. The CSOD results were validated by the consistency of the values with reported binding affinities. In addition, we found that CSOD can tolerate up to 3.9% dimethyl sulfoxide (DMSO) and up to 10% serum, which shows its compatibility with realistic sample conditions.

Development of dichloroacetamide pyrimidines as pyruvate dehydrogenase kinase inhibitors to reduce cancer cell growth: synthesis and biological evaluation

The synthesis and biological assays were described herein to firstly identify a novel PDK1 inhibitor.

Antiproliferative activities of halogenated pyrrolo[3,2-d]pyrimidines

In vitro evaluation of the halogenated pyrrolo[3,2-d]pyrimidines identified antiproliferative activities in compounds 1 and 2 against four different cancer cell lines. Upon screening of a series of pyrrolo[3,2-d]pyrimidines, the 2,4-Cl compound 1 was found to exhibit antiproliferative activity at low micromolar concentrations. Introduction of iodine at C7 resulted in significant enhancement of potency by reducing the IC50 into sub-micromolar levels, thereby suggesting the importance of a halogen at C7. This finding was further supported by an increased antiproliferative effect for 4 as compared to 3. Cell-cycle and apoptosis studies conducted on the two potent compounds 1 and 2 showed differences in their cytotoxic mechanisms in triple negative breast cancer MDA-MB-231 cells, wherein compound 1 induced cells to accumulate at the G2/M stage with little evidence of apoptotic death. In contrast, compound 2 robustly induced apoptosis with concomitant G2/M cell cycle arrest in this cell model.

Efficient solution-phase synthesis of 4,5,7-trisubstituted pyrrolo[3,2-d]pyrimidines

We have developed an efficient and robust route to synthesize 4,5,7-trisubstituted pyrrolo[3,2-d]pyrimidines as potent kinase inhibitors. This solution-phase synthesis features a SNAr substitution reaction, cross-coupling reaction, one-pot reduction/reductive amination and N-alkylation reaction. These reactions occur rapidly with high yields and have broad substrate scopes. A variety of groups can be selectively introduced into the N5 and C7 positions of 4,5,7-trisubstituted pyrrolopyrimidines at a late stage of the synthesis, thereby providing a highly efficient approach to explore the structure-activity relationships of pyrrolopyrimidine derivatives. Four synthetic analogs have been profiled against a panel of 48 kinases and a new and selective FLT3 inhibitor 9 is identified.

A study of the specificity of lymphocytes in nevirapine-induced skin rash

Nevirapine treatment can cause a skin rash. We developed an animal model of this rash and determined that the 12-hydroxylation metabolic pathway is responsible for the rash, and treatment of animals with 12-OH-nevirapine also leads to a rash. In the present study, we investigated the specificity of lymphocytes in nevirapine-induced skin rash. Brown Norway rats were treated with nevirapine or 12-OH-nevirapine to induce a rash. Lymph nodes were removed, and the response of lymphocytes to nevirapine and its metabolites/analogs was determined by cytokine production (enzyme-linked immunosorbent assay, enzyme-linked immunosorbent spot assay, and Luminex) and proliferation (alamar blue assay). Subsets of lymphocytes were depleted to determine which cells were responsible for cytokine production. Lymphocytes from animals rechallenged with nevirapine proliferated to nevirapine, but not to 12-OH-nevirapine or 4-chloro-nevirapine. They also produced interferon-gamma (IFN-gamma) when exposed to nevirapine, significantly less when exposed to 4-chloro-nevirapine, and very little when exposed to 12-OH-nevirapine, even though oxidation to 12-OH-nevirapine is required to induce the rash. Moreover, the specificity of lymphocytes from 12-OH-nevirapine-treated rats was the same, i.e., responding to nevirapine more than to 12-OH-nevirapine, even though these animals had never been exposed to nevirapine. A Luminex immunoassay showed that a variety of other cytokines/chemokines were also produced by nevirapine-stimulated lymphocytes. CD4(+) cells were the major source of IFN-gamma. The specificity of lymphocytes in activation assays cannot be used to determine what initiated an immune response. This has significant implications for understanding the evolution of an immune response and the basis of the pharmacological interaction hypothesis.

Novel orally active NPY Y5 receptor antagonists: Synthesis and structure-activity relationship of spiroindoline class compounds

Spiroindoline urea derivatives, designed to act as NPY Y5 receptor antagonists, were synthesized and their structure-activity relationships were investigated. Of these derivatives, compound 3a showed good Y5 binding affinity with favorable pharmacokinetic properties. Compound 3a significantly inhibited bPP Y5 agonist-induced food intake in rats, and suppressed body weight gain in DIO mice.

Identification of novel and orally active spiroindoline NPY Y5 receptor antagonists

A series of spiroindoline-3,4'-piperidine derivatives were synthesized and evaluated for their binding affinities and antagonistic activities at Y5 receptors. Potent Y5 antagonists were tested for their oral bioavailabilities and brain penetration in rats. Some of the antagonists showed good oral bioavailability and/or good brain penetration. In particular, compound 6e was orally bioavailable and brain penetrant, and oral administration of 6e inhibited bPP-induced food intake in rats with a minimum effective dose of 10mg/kg.

Syntheses and structure-activity relationships of novel, potent, and selective trans-2-[3-oxospiro[isobenzofuran-1(3H),1'-cyclohexan]-4'-yl]benzimidazole NPY Y5 receptor antagonists

Syntheses and structure-activity relationships of a novel class of 2-[3-oxospiro[isobenzofuran-1(3H),1'-cyclohexan]-4'-yl]benzimidazole NPY Y5 receptor antagonists are described. Optimization of the lead compound 2a by incorporating substituents into the 5-position or into both the 5- and 6-positions of the benzimidazole core part led to the identification of 5-(5-methyl-1,2,4-oxadiazol-2-yl)benzimidazole (2r: IC(50)=3.3 nM) and 5-(2-methyltetrazol-5-yl)benzimidazole (2u: IC(50)=5.9 nM), both of which are potent, selective, and orally bioavailable Y5 receptor antagonists.

Regioselective (site-selective) functionalisation of unsaturated halogenated nitrogen, oxygen and sulfur heterocycles by Pd-catalysed cross-couplings and direct arylation processes

This tutorial review focuses on several practical synthetic transformations utilising palladium catalysis that facilitate the synthesis of functionalized unsaturated heterocycles in a regioselective (site-selective) manner. Cross-couplings of electron-deficient, electron-neutral and electron-rich unsaturated halogenated heterocycles with various organometallic reagents, and other types of nucleophiles, are detailed. Direct arylation of electron-rich unsaturated heterocyclic compounds by C-H functionalization is also presented.

Investigational therapies in the treatment of obesity

Obesity is a major public health concern and environmental factors are involved in its development. The hypothalamus is a primary site for the integration of signals for the regulation of energy homeostasis. Dysregulation of these pathways can lead to weight loss or gain. Some drugs in development can have favourable effects on body weight, acting on some of these pathways and leading to responses resulting in weight loss. Strategies for the management of weight reduction include exercise, diet, behavioural therapy, drug therapy and surgery. Investigational antiobesity medications can modulate energy homeostasis by stimulating catabolic or inhibiting anabolic pathways. Investigational drugs stimulating catabolic pathways consist of leptin, agonists of melanocortin receptor-4, 5-HT and dopamine; bupropion, growth hormone fragments, cholecystokinin subtype 1 receptor agonist, peptide YY3-36, oxyntomodulin, ciliary neurotrophic factor analogue, beta3-adrenergic receptor agonists, adiponectin derivatives and glucagon-like peptide-1. On the other hand, investigational drugs inhibiting anabolic pathways consist of the ghrelin receptor, neuropeptide Y receptor and melanin-concentrating hormone-1 antagonists; somatostatin analogues, peroxisome proliferator-activated receptor-gamma and -beta/delta antagonists, gastric emptying retardation agents, pancreatic lipase inhibitors, topiramate and cannabinoid-1 receptor antagonists. These differing approaches are reviewed and commented on in this article.

TDIQ (5,6,7,8-tetrahydro-1,3-dioxolo[4,5-g]isoquinoline) inhibits the consumption of “snacks” in mice

There is considerable evidence that alpha2-adrenergic receptor activity exerts a pivotal role in initiation of feeding behavior. The appetite suppressant and monoamine release effects of TDIQ (5,6,7,8-tetrahydro-1,3-dioxolo[4,5-g]isoquinoline), a putative selective alpha2-adrenergic compound, were compared to those of fenfluramine, a reference drug that produces an anorectic effect via presynaptic release and reuptake inhibition of serotonin. The drugs were administered to two groups of mice that had learned to consume either sweet milk or chocolate pellets (i.e. "snacks") during the low-activity/reduced-feeding "light" portion of their light/dark cycle. The selectivity of the drugs to suppress the consumption of snacks was determined by comparing doses of each drug that inhibited the animals' consumption of snacks to doses of each drug that have been shown, or were shown, to impact the motor (i.e. locomotor, rotarod, and inclined-screen side effect-like tests) or conditioned taste aversion (CTA) behavior of mice. An evaluation of TDIQ as a releaser of monoamines was determined in rodent brain synaptosomes. The administration of TDIQ or fenfluramine inhibited the consumption of the snacks, and a comparison of their ED50 doses indicated that TDIQ is about 3 times more potent than fenfluramine (1.3 mg/kg vs. 4.2 mg/kg, respectively) in the sweet milk test and almost equipotent to fenfluramine (19.4 mg/kg vs. 18.4 mg/kg, respectively) in the chocolate pellet assay. The selectivity of the appetite suppressant effect of TDIQ was differentiated from that of fenfluramine on the basis that TDIQ exhibited a wide separation between its dose-response effects that suppressed snack consumption and its minimal effects in tests that measured behavioral impairment. Moreover, TDIQ was distinguished from fenfluramine in that it displayed very low potencies as a presynaptic releaser of monoamines. Finally, TDIQ (0.3 mg/kg-30.0 mg/kg) did not induce a conditioned taste aversion. TDIQ may represent a novel chemical entity that exhibits a significantly favorable therapeutic-like (i.e. appetite suppressant) effect to side effect-like ratio.

Design and Synthesis of a Tetracyclic Pyrimidine-Fused Benzodiazepine Library

Method development for a heterocyclic library which entails novel scaffolds of benzodiazepines fused with various heterocycles, such as pyrimidines, indolines, and tetrahydroquinolines, was accomplished. The new synthetic strategy is based on an electrophilic cyclization reaction involving an iminium intermediate formed by the corresponding aminopyrimidine with a carbonyl compound to give the desired heterocycles in high yields. Subsequent replacement of the chloro group in the resulted structures with a nucleophile, such as boronic acids, amines, alcohols and thiols, led to a library of privileged compounds with up to eight accessible diversity points.

The purines: potent and versatile small molecule inhibitors and modulators of key biological targets

The goal of this review is to highlight the wide range of biological activities displayed by purines, with particular emphasis on new purine-based agents which find potential application as chemical-biology tools and/or therapeutic agents. The expanding interest in the biological properties of polyfunctionalized purine derivatives issues, in large part, from the development of rapid high-throughput screening essays for new protein targets, and the corresponding development of efficient synthetic methodology adapted to the construction of highly diverse purine libraries. Purine-based compounds have found new applications as inducers of interferon and lineage-committed cell dedifferentiation, agonists and antagonists of adenosine receptors, ligands of corticotropin-releasing hormone receptors, and as inhibitors of HSP90, Src kinase, p38alpha MAP kinase, sulfotransferases, phosphodiesterases, and Cdks. The scope of application of purines in biology is most certainly far from being exhausted. Testing purine derivatives against the multitude of biological targets for which small molecule probes have not yet been found should thus be a natural reflex.

A review of melanocortin receptor small molecule ligands

The melanocortin system (MC) is implicated in the regulation of a variety of physiological pathways including pigmentation, steroid function, energy homeostasis, food intake, obesity, cardiovascular, sexual function, and normal gland regulation. The melanocortin system consists of five receptors identified to date (MC1-5R), melanocortin agonists derived from the pro-opiomelanocortin prohormone (POMC) and two naturally existing antagonists. Melanocortin receptor ligand structure-activity studies have been performed since the 1960s, primarily focused on the pigmentation aspect of physiology. During the 1990s, the melanocortin-4 receptor was identified to play a significant physiological role in the regulation of both food intake and obesity. Subsequently, a concerted drug design effort has focused on the design and discovery of melanocortin receptor small molecules. Herein, we present an overview of melanocortin receptor heterocyclic small molecules.

Synthesis of Tricyclic 4-Chloro-pyrimido[4,5-b][1,4]benzodiazepines

[reaction: see text] A novel methodology was developed for the efficient synthesis of 4-chloro-pyrimido[4,5-b][1,4]benzodiazepines. The key is the intramolecular Friedel-Crafts cyclization of 5-amino-4-(N-substituted)anilino-6-chloropyrimidine with either a carboxylic acid or its derivatives to construct the 4-chloro-pyrimido[4,5-b][1,4]benzodiazepine core. Subsequent nucleophilic substitution allows the introduction of one more diversity point in the target molecules. This strategy provides an efficient method to access a library of compounds based on privileged substructures that are of great interest in drug discovery.