Overcoming Limitations in Decarboxylative Arylation via Ag-Ni Electrocatalysis.

A useful protocol for achieving decarboxylative cross-coupling (DCC) of redox-active esters (RAE, isolated or generated in situ) and halo(hetero)arenes is reported. This pragmatically focused study employs a unique Ag-Ni electrocatalytic platform to overcome numerous limitations that have plagued this strategically powerful transformation. In its optimized form, coupling partners can be combined in a surprisingly simple way: open to the air, using technical-grade solvents, an inexpensive ligand and Ni source, and substoichiometric AgNO3, proceeding at room temperature with a simple commercial potentiostat. Most importantly, all of the results are placed into context by benchmarking with state-of-the-art methods. Applications are presented that simplify synthesis and rapidly enable access to challenging chemical space. Finally, adaptation to multiple scale regimes, ranging from parallel milligram-based synthesis to decagram recirculating flow is presented.

Mechanism of hepatobiliary toxicity of the LPA1 antagonist BMS-986020 developed to treat idiopathic pulmonary fibrosis: Contrasts with BMS-986234 and BMS-986278.

In a Phase 2 clinical trial, BMS-986020, a lysophosphatidic acid receptor-1 (LPA1) antagonist, produced hepatobiliary toxicity (increased ALT, AST, and ALP; cholecystitis) and increases in plasma bile acids (BA). Nonclinical investigations conducted to identify a potential mechanism(s) for this toxicity examined BMS-986020 and two LPA1 antagonists structurally distinct from BMS-986020 (BMS-986234 and BMS-986278). BMS-986020 inhibited hepatic BA efflux transporters BSEP (IC50 1.8 µM), MRP3 (IC50 22 µM), and MRP4 (IC50 6.2 µM) and inhibited BA canalicular efflux in human hepatocytes (68% at 10 µM). BMS-986020 inhibited mitochondrial function (basal and maximal respiration, ATP production, and spare capacity) in human hepatocytes and cholangiocytes at ≥10 µM and inhibited phospholipid efflux in human hepatocytes (MDR3 IC50 7.5 µM). A quantitative systems toxicology analysis (DILIsym®), considering pharmacokinetics, BA homeostasis, mitochondrial function, oxidative phosphorylation, and reactive intermediates performed for BMS-986020 recapitulated clinical findings ascribing the effects to BA transporter and mitochondrial electron transport chain inhibition. BMS-986234 and BMS-986278 minimally inhibited hepatic BA transporters (IC50 ≥20 µM) and did not inhibit MDR3 activity (IC50 >100 µM), nor did BMS-986234 inhibit BA efflux (≤50 µM) or mitochondrial function (≤30 µM) (BMS-986278 not evaluated). Multiple mechanisms may be involved in the clinical toxicity observed with BMS-986020. The data indicate that this toxicity was unrelated to LPA1 antagonism since the mechanisms that likely influenced the adverse clinical outcome of BMS-986020 were not observed with equipotent LPA1 antagonists BMS-986234 and BMS-986278. This conclusion is consistent with the lack of hepatobiliary toxicity in nonclinical and clinical safety studies with BMS-986278.

Structural and Thermal Characterization of Halogenated Azidopyridines: Under-Reported Synthons for Medicinal Chemistry.

Owing to their participation in Click reactions, bifunctional azides are valuable intermediates in the preparation of medicines and biochemical tool compounds. Despite the privileged nature of pyridines among pharmaceutical scaffolds, reports of the synthesis and characterization of azidopyridines bearing a halogen substituent for further elaboration are almost completely unknown in the literature. As azidopyridines carry nearly equal numbers of nitrogen and carbon atoms, we hypothesized that safety concerns limited the application of these useful bifunctional building blocks in medicinal and biological chemistry. To address this concern, we prepared and characterized nine azidopyridines bearing a single fluorine, chlorine, or bromine atom. All were examined by differential scanning calorimetry (DSC), in which they demonstrated exotherms of 228-326 kJ/mol and onset temperatures between 119 and 135 °C. Selected azidopyridines were advanced to mechanical stress testing, in which impact sensitivity was noted for one regioisomer of C5H3FN4. The utility of these versatile intermediates was demonstrated through their use in a variety of Click reactions and the diversification of the halogen handles.

A tautomeric ligand enables directed C‒H hydroxylation with molecular oxygen.

Hydroxylation of aryl carbon-hydrogen bonds with transition metal catalysts has proven challenging when oxygen is used as the oxidant. Here, we report a palladium complex bearing a bidentate pyridine/pyridone ligand that efficiently catalyzes this reaction at ring positions adjacent to carboxylic acids. Infrared, x-ray, and computational analysis support a possible role of ligand tautomerization from mono-anionic (L,X) to neutral (L,L) coordination in the catalytic cycle of aerobic carbon-hydrogen hydroxylation reaction. The conventional site selectivity dictated by heterocycles is overturned by this catalyst, thus allowing late-stage modification of compounds of pharmaceutical interest at previously inaccessible sites.

Discovery of an Oxycyclohexyl Acid Lysophosphatidic Acid Receptor 1 (LPA1) Antagonist BMS-986278 for the Treatment of Pulmonary Fibrotic Diseases.

The oxycyclohexyl acid BMS-986278 (33) is a potent lysophosphatidic acid receptor 1 (LPA1) antagonist, with a human LPA1 Kb of 6.9 nM. The structure-activity relationship (SAR) studies starting from the LPA1 antagonist clinical compound BMS-986020 (1), which culminated in the discovery of 33, are discussed. The detailed in vitro and in vivo preclinical pharmacology profiles of 33, as well as its pharmacokinetics/metabolism profile, are described. On the basis of its in vivo efficacy in rodent chronic lung fibrosis models and excellent overall ADME (absorption, distribution, metabolism, excretion) properties in multiple preclinical species, 33 was advanced into clinical trials, including an ongoing Phase 2 clinical trial in patients with lung fibrosis (NCT04308681).

Nickel-Catalyzed 1,2-Carboamination of Alkenyl Alcohols.

An alcohol-directed, nickel-catalyzed three-component umpolung carboamination of unactivated alkenes with aryl/alkenylboronic esters and electrophilic aminating reagents is reported. This transformation is enabled by specifically tailored O-(2,6-dimethoxybenzoyl)hydroxylamine electrophiles that suppress competitive processes, including undesired ß-hydride elimination and transesterification between the alcohol substrate and electrophile. The reaction delivers the desired 1,2-carboaminated products with generally high regio- and syn-diastereoselectivity and exhibits a broad scope of coupling partners and alkenes, including complex natural products. Various mechanistic experiments and analysis of the stereochemical outcome with a cyclic alkene substrate, as confirmed by X-ray crystallographic analysis, support alcohol-directed syn-insertion of an organonickel(I) species.

Catalytic Ring Expansions of Cyclic Alcohols Enabled by Proton-Coupled Electron Transfer.

We report here a catalytic method for the modular ring expansion of cyclic aliphatic alcohols. In this work, proton-coupled electron transfer activation of an allylic alcohol substrate affords an alkoxy radical intermediate that undergoes subsequent C-C bond cleavage to furnish an enone and a tethered alkyl radical. Recombination of this alkyl radical with the revealed olefin acceptor in turn produces a ring-expanded ketone product. The regioselectivity of this C-C bond-forming event can be reliably controlled via substituents on the olefin substrate, providing a means to convert a simple N-membered ring substrate to either n+1 or n+2 ring adducts in a selective fashion.

Selective C-H Halogenation with a Highly Fluorinated Manganese Porphyrin.

The selective C-H functionalization of aliphatic molecules remains a challenge in organic synthesis. While radical chain halogenation reactions provide efficient access to many halogenated molecules, the use of typical protocols for the selective halogenation of electron-deficient and strained aliphatic molecules is rare. Herein, we report selective C-H chlorination and fluorination reactions promoted by an electron-deficient manganese pentafluorophenyl porphyrin catalyst, Mn(TPFPP)Cl. This catalyst displays superior properties for the aliphatic halogenation of recalcitrant, electron-deficient, and strained substrates with unique regio- and stereoselectivity. UV/Vis analysis during the course of the reaction indicated that an oxo-MnV species is responsible for hydrogen-atom abstraction. The observed stereoselectivity results from steric interactions between the bulky porphyrin ligand and the intermediate substrate radical in the halogen rebound step.

Ligand-accelerated non-directed C-H functionalization of arenes.

The directed activation of carbon-hydrogen bonds (C-H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups. Palladium-catalysed non-directed C-H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts. Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used, which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C-H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C-H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C-H functionalization.

Discovery and Preclinical Evaluation of BMS-711939, an Oxybenzylglycine Based PPARα Selective Agonist.

BMS-711939 (3) is a potent and selective peroxisome proliferator-activated receptor (PPAR) α agonist, with an EC50 of 4 nM for human PPARα and >1000-fold selectivity vs human PPARγ (EC50 = 4.5 µM) and PPARδ (EC50 > 100 µM) in PPAR-GAL4 transactivation assays. Compound 3 also demonstrated excellent in vivo efficacy and safety profiles in preclinical studies and thus was chosen for further preclinical evaluation. The synthesis, structure-activity relationship (SAR) studies, and in vivo pharmacology of 3 in preclinical animal models as well as its ADME profile are described.

Ligand-Promoted Borylation of C(sp(3))-H Bonds with Palladium(II) Catalysts.

A quinoline-based ligand effectively promotes the palladium-catalyzed borylation of C(sp(3))-H bonds. Primary ß-C(sp(3))-H bonds in carboxylic acid derivatives as well as secondary C(sp(3))-H bonds in a variety of carbocyclic rings, including cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes, and cycloheptanes, can thus be borylated. This directed borylation method complements existing iridium(I)- and rhodium(I)-catalyzed C-H borylation reactions in terms of scope and operational conditions.

Utilization of the Zucker Diabetic Fatty (ZDF) Rat Model for Investigating Hypoglycemia-related Toxicities.

Glucokinase (GK) catalyzes the initial step in glycolysis and is a key regulator of glucose homeostasis. Therefore, glucokinase activators (GKa) have potential benefit in treating type 2 diabetes. Administration of a Bristol-Myers Squibb GKa (BMS-820132) to healthy euglycemic Sprague-Dawley (SD) rats and beagle dogs in 1 mo toxicology studies resulted in marked and extended hypoglycemia with associated clinical signs of toxicity and degenerative histopathological changes in the stomach, sciatic nerve, myocardium, and skeletal muscles at exposures comparable to those expected at therapeutic clinical exposures. To investigate whether these adverse effects were secondary to exaggerated pharmacology (prolonged hypoglycemia), BMS-820132 was administered daily to male Zucker diabetic fatty (ZDF) rats for 1 mo. ZDF rats are markedly hyperglycemic and insulin resistant. BMS-820132 did not induce hypoglycemia, clinical signs of hypoglycemia, or any of the histopathologic adverse effects observed in the 1 mo toxicology studies at exposures that exceeded those observed in SD rats and dogs. This indicates that the toxicity observed in euglycemic animals was secondary to the exaggerated pharmacology of potent GK activation. This study indicates that ZDF rats, with conventional toxicity studies, are a useful disease model for testing antidiabetic agents and determining toxicities that are independent of prolonged hypoglycemia.

Synthesis and biological evaluation of novel pyrrolidine acid analogs as potent dual PPARα/γ agonists.

The design, synthesis and structure-activity relationships of a novel series of 3,4-disubstituted pyrrolidine acid analogs as PPAR ligands is outlined. In both the 1,3- and 1,4-oxybenzyl pyrrolidine acid series, the preferred stereochemistry was shown to be the cis-3R,4S isomer, as exemplified by the potent dual PPARα/γ agonists 3k and 4i. The N-4-trifluoromethyl-pyrimidinyl pyrrolidine acid analog 4i was efficacious in lowering fasting glucose and triglyceride levels in diabetic db/db mice.

The strength/weakness of the AJCC/UICC staging system (7th edition) for nasopharyngeal cancer and suggestions for future improvement.

BACKGROUND AND PURPOSE: To evaluate the current AJCC/UICC staging system (7th edition) for nasopharyngeal carcinoma and to explore for future improvement. MATERIALS AND METHODS: A total of 985 patients, initially staged with preceding 5-6th edition, were retrospectively re-staged with the 7th edition. All were assessed by magnetic resonance imaging, and all 945 non-disseminated patients were irradiated with conformal/intensity-modulated technique. RESULTS: Staging factors by both the 5-6th edition and the 7th edition were strongly significance for important endpoints (p<0.001). Down-staging of the previous T2a to T1 and, stages IIA to I in the 7th edition was appropriate. However, the impacts on overall stage distribution and prognostication were minimal. Further down-staging of the current T2 to T1, N2 to N1, stages II to I, and merging of N3a and N3b, stages IVA and IVB were suggested. With the 7th edition, the 5-year disease-specific survival (DSS) was 100% for stage I, 95% for II, 90% for III, 67% for IVA, 68% for IVB and 18% for IVC. The corresponding DSS for the proposed stages I, II, III and IV were 95%, 86%, 67% and 18%, respectively. CONCLUSIONS: The changes introduced in the 7th edition were appropriate, but the magnitude of improvement was minimal. With improving results by modern management, further simplification of the staging system is suggested. The proposed system could lead to more accurate prognostication, further validation is warranted.

Plasma stability-dependent circulation of acyl glucuronide metabolites in humans: how circulating metabolite profiles of muraglitazar and peliglitazar can lead to misleading risk assessment.

Muraglitazar and peliglitazar, two structural analogs differing by a methyl group, are dual peroxisome proliferator-activated receptor-α/γ activators. Both compounds were extensively metabolized in humans through acyl glucuronidation to form 1-O-ß-acyl glucuronide (AG) metabolites as the major drug-related components in bile, representing at least 15 to 16% of the dose after oral administration. Peliglitazar AG was the major circulating metabolite, whereas muraglitazar AG was a very minor circulating metabolite in humans. Peliglitazar AG circulated at lower concentrations in animal species than in humans. Both compounds had a similar glucuronidation rate in UDP-glucuronic acid-fortified human liver microsomal incubations and a similar metabolism rate in human hepatocytes. Muraglitazar AG and peliglitazar AG were chemically synthesized and found to be similarly oxidized through hydroxylation and O-demethylation in NADPH-fortified human liver microsomal incubations. Peliglitazar AG had a greater stability than muraglitazar AG in incubations in buffer, rat, or human plasma (pH 7.4). Incubations of muraglitazar AG or peliglitazar AG in plasma produced more aglycon than acyl migration products compared with incubations in the buffer. These data suggested that the difference in plasma stability, not differences in intrinsic formation, direct excretion, or further oxidation of muraglitazar AG or peliglitazar AG, contributed to the observed difference in the circulation of these AG metabolites in humans. The study demonstrated the difficulty in doing risk assessment based on metabolite exposure in plasma because the more reactive muraglitazar AG would not have triggered a threshold of concern based on the recent U.S. Food and Drug Administration guidance on Metabolites in Safety Testing, whereas the more stable peliglitazar AG would have.

Metabolism and disposition of 14C-labeled peliglitazar in humans.

The metabolism and disposition of dual (14)C-labeled peliglitazar, a dual α/γ peroxisome proliferator-activated receptor activator, was investigated in 10 healthy male subjects with and without bile collection (groups 1 and 2) after a single 10-mg oral dose. Serial blood samples, urine, and feces (0-240 h) as well as bile samples (3-8 h after dosing from group 2 subjects) were collected. The maximum plasma concentration (C(max)) of drug was reached at approximately 1 h and the elimination half-life (t(1/2)) was approximately 3.5 h. The exposure to drug metabolites (C(max) and area under the plasma concentration versus time curve) was not significantly different between the two groups. The parent compound and its 1-O-ß-acyl-glucuronide conjugate were the major components in plasma; other circulating metabolites, including several other glucuronide conjugates, were minor components at all time points. The major portion of the radioactive dose was recovered in feces (94% for group 1 and 32% for group 2). Approximately 24% of the radioactive dose was recovered in the bile from group 2 subjects, nearly all of which was assigned as glucuronides of peliglitazar and its oxidative metabolites (M14, M14a, M14b, M15, M15a, M15b, and M17). In contrast, fecal samples contained peliglitazar and its oxidative metabolites resulting from aliphatic/aryl hydroxylation, and O-demethylation. These results suggested that the major clearance pathway of peliglitazar was through biliary elimination of glucuronide conjugates, which were hydrolyzed to peliglitazar and its oxidative metabolites in the intestines before excretion.

Synthesis and structure-activity relationships of 2-aryl-4-oxazolylmethoxy benzylglycines and 2-aryl-4-thiazolylmethoxy benzylglycines as novel, potent PPARalpha selective activators- PPARalpha and PPARgamma selectivity modulation.

The synthesis and follow-up SAR studies of our development candidate 1 by incorporating 2-aryl-4-oxazolylmethoxy and 2-aryl-4-thiazolylmethoxy moieties into the oxybenzylglycine framework of the PPARalpha/gamma dual agonist muraglitazar is described. SAR studies indicate that different substituents on the aryloxazole/thiazole moieties as well as the choice of carbamate substituent on the glycine moiety can significantly modulate the selectivity of PPARalpha versus PPARgamma. Potent, highly selective PPARalpha activators 2a and 2l, as well as PPARalpha activators with significant PPARgamma activity, such as 2s, were identified. The in vivo pharmacology of these compounds in preclinical animal models as well as their ADME profiles are discussed.

Discovery of an oxybenzylglycine based peroxisome proliferator activated receptor alpha selective agonist 2-((3-((2-(4-chlorophenyl)-5-methyloxazol-4-yl)methoxy)benzyl)(methoxycarbonyl)amino)acetic acid (BMS-687453).

An 1,3-oxybenzylglycine based compound 2 (BMS-687453) was discovered to be a potent and selective peroxisome proliferator activated receptor (PPAR) alpha agonist, with an EC(50) of 10 nM for human PPARalpha and approximately 410-fold selectivity vs human PPARgamma in PPAR-GAL4 transactivation assays. Similar potencies and selectivity were also observed in the full length receptor co-transfection assays. Compound 2 has negligible cross-reactivity against a panel of human nuclear hormone receptors including PPARdelta. Compound 2 demonstrated an excellent pharmacological and safety profile in preclinical studies and thus was chosen as a development candidate for the treatment of atherosclerosis and dyslipidemia. The X-ray cocrystal structures of the early lead compound 12 and compound 2 in complex with PPARalpha ligand binding domain (LBD) were determined. The role of the crystal structure of compound 12 with PPARalpha in the development of the SAR that ultimately resulted in the discovery of compound 2 is discussed.

Design, synthesis and structure-activity relationships of azole acids as novel, potent dual PPAR alpha/gamma agonists.

The design, synthesis and structure-activity relationships of a novel series of N-phenyl-substituted pyrrole, 1,2-pyrazole and 1,2,3-triazole acid analogs as PPAR ligands are outlined. The triazole acid analogs 3f and 4f were identified as potent dual PPARalpha/gamma agonists both in binding and functional assays in vitro. The 3-oxybenzyl triazole acetic acid analog 3f showed excellent glucose and triglyceride lowering in diabetic db/db mice.

Major late toxicities after conformal radiotherapy for nasopharyngeal carcinoma-patient- and treatment-related risk factors.

PURPOSE: To retrospectively analyze the factors affecting late toxicity for nasopharyngeal carcinoma. METHODS AND MATERIALS: Between 1998 and 2003, 422 patients were treated with a conformal technique with 2-Gy daily fractions to a total dose of 70 Gy. Conventional fractionation (5 fractions weekly) was used in 232 patients and accelerated fractionation (6 fractions weekly) in 190 patients. One hundred seventy-one patients were treated with the basic radiotherapy course alone (Group 1), 55 patients had an additional boost of 5 Gy in 2 fractions (Group 2), and 196 patients underwent concurrent cisplatin-based chemotherapy (Group 3). RESULTS: The 5-year overall toxicity rate was significantly greater in Group 3 than in Group 1 (37% vs. 27%, p = 0.009). Although the overall rate in Group 2 was not elevated (28% vs. 27%, p = 0.697), a significant increase in temporal lobe necrosis was observed (4.8% vs. 0%, p = 0.015). Multivariate analyses showed that age and concurrent chemotherapy were significant factors. The hazard ratio of overall toxicity attributed to chemotherapy was 1.99 (95% confidence interval, 1.32-2.99, p = 0.001). The mean radiation dose to the cochlea was another significant factor affecting deafness, with a hazard ratio of 1.03 (95% confidence interval, 1.01-1.05, p = 0.005) per 1-Gy increase. The cochlea that received >50 Gy had a significantly greater deaf rate (Group 1, 18% vs. 7%; and Group 3, 22% vs. 14%). CONCLUSION: The therapeutic margin for nasopharyngeal carcinoma is extremely narrow, and a significant increase in brain necrosis could result from dose escalation. The significant factors affecting the risk of deafness included age, concurrent chemoradiotherapy, and greater radiation dose to the cochlea.