Biphenylsulfonamide endothelin receptor antagonists. 4. Discovery of N-[[2'-[[(4,5-dimethyl-3-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]- 2-yl]methyl]-N,3,3-trimethylbutanamide (BMS-207940), a highly potent and orally active ET(A) selective antagonist

A Study on Synthesis of Chalcone Derived -5- Membered Isoxazoline and Isoxazole Scaffolds

Chalcone-derived Isoxazole scaffolds remain the central focus because of their greater biological, clinical, and pharmacological properties. The present study reviews the synthesis of various chalcone derived - 5- Membered Isoxazoline and Isoxazole Scaffolds with the available literature until 2021. Keywords: Chalcones, Isoxazoles, Isoxazolines, Biological and Pharmacological properties.

Amide Iridium Complexes As Catalysts for Transfer Hydrogenation Reduction of N-sulfonylimine

Sulfonamide moieties widely exist in natural products, biologically active substance, and pharmaceuticals. Here, an efficient water-soluble amide iridium complexes-catalyzed transfer hydrogenation reduction of N-sulfonylimine is developed, which can be carried out under environmentally friendly conditions, affording a series of sulfonamide compounds in excellent yields (96-98%). In comparison with organic solvents, water is shown to be critical for a high catalytic transfer hydrogenation reduction in which the catalyst loading can be as low as 0.001 mol %. These amide iridium complexes are easy to synthesize, one structure of which was determined by single-crystal X-ray diffraction. This protocol gives an operationally simple, practical, and environmentally friendly strategy for synthesis of sulfonamide compounds.

Nickel-Catalyzed Cross-Dehydrogenative Coupling of α-C(sp3)-H Bonds in N-Methylamides with C(sp3)-H Bonds in Cyclic Alkanes

A nickel-catalyzed cross-dehydrogenative coupling reaction of α-C(sp³)-H bonds in N-methylamides with C(sp³)-H bonds from cyclic alkanes has been developed, which offers a cheap transition-metal-catalyzed C-H activation method for amides without the requirement for any extraneous directing group. This new strategy is highly selective and tolerates a variety of functional groups. Mechanistic investigations into the reaction process are also described in detail.

Oxidation-Reduction Condensation of Diazaphosphites for Carbon-Heteroatom Bond Formation Based on Mitsunobu Mechanism

An efficient oxidation-reduction condensation reaction of diazaphosphites with various nonacidic pronucleophiles in the presence of DIAD as a weak oxidant has been developed for carbon-heteroatom bond formation. This mild process affords structurally diverse tertiary amines, secondary amines, esters, ethers, and thioethers in moderate to excellent yields. The selective synthesis of secondary amines from primary amines has been achieved. Importantly, a practical application to the synthesis of antiparkinsonian agent piribedil has been demonstrated.

Sulfonamide vs. sulfonimide: tautomerism and electronic structure analysis of N-heterocyclic arenesulfonamides

Experimental and computational studies suggest a preference toward the sulfonimide tautomer in N-heterocyclic arenesulfonamide.

Integration of oxidative arylation with sulfonyl migration: one-pot tandem synthesis of densely functionalized (NH)-pyrroles

A one-pot synthesis of 2-aryl-3-alkyl/aryl-sulfonyl-(NH)-pyrroles from N-sulfonylpyrroles, developed for the first time, via palladium-catalyzed oxidative C-2 arylation followed by sulfonyl migration is described.

Nickel-catalyzed product-controllable amidation and imidation of sp3 C–H bonds in substituted toluenes with sulfonamides

A nickel-catalyzed product-controllable imidation and amidation of sp³ C–H bonds in substituted toluenes with sulfonamides were developed.

Endothelin-Receptor Antagonists beyond Pulmonary Arterial Hypertension: Cancer and Fibrosis

The endothelin axis and in particular the two endothelin receptors, ETA and ETB, are targets for therapeutic intervention in human diseases. Endothelin-receptor antagonists are in clinical use to treat pulmonary arterial hypertension and have been under clinical investigation for the treatment of several other diseases, such as systemic hypertension, cancer, vasospasm, and fibrogenic diseases. In this Perspective, we review the molecules that have been evaluated in human clinical trials for the treatment of pulmonary arterial hypertension, as well as other cardiovascular diseases, cancer, and fibrosis. We will also discuss the therapeutic consequences of receptor selectivity with regard to ETA-selective, ETB-selective, or dual ETA/ETB antagonists. We will also consider which chemical characteristics are relevant to clinical use and the properties of molecules necessary for efficacy in treating diseases against which known molecules displayed suboptimal efficacy.

Isoxazole derivatives as potent transient receptor potential melastatin type 8 (TRPM8) agonists

Modulation of the transient receptor potential melastatin type-8 (TRPM8), the receptor for menthol acting as the major sensor for peripheral innocuous cool temperatures, has several important applications in pharmaceutical, food and cosmetic industries. In the present study, we designed 12 isoxazole derivatives and tested their pharmacological properties both in F11 sensory neurons in vitro, and in an in vivo model of cold allodynia. In F11 sensory neurons, single-cell Ca(2+)-imaging experiments revealed that, when compared to menthol, some newly-synthesized compounds were up to 200-fold more potent, though none of them showed an increased efficacy. Some isoxazole derivatives potentiated allodynic responses elicited by acetone when administered to rats subjected to sciatic nerve ligation; when compared to menthol, these compounds were efficacious at earlier (0-2 min) but not later (7-9 or 14-16 min) time points. Docking experiments performed in a human TRPM8 receptor model revealed that newly-synthesized compounds might adopt two possible conformations, thereby allowing to distinguish "menthol-like" compounds (characterized by high efficacy/low potency), and "icillin-like" compounds (with high potency/low efficacy). Collectively, these data provide rationale structure-activity relationships for isoxazole derivatives acting as TRPM8 agonists, and suggest their potential usefulness for cold-evoked analgesia.

Tetrahydrobiopterin biosynthesis as an off-target of sulfa drugs

The introduction of sulfa drugs for the chemotherapy of bacterial infections in 1935 revolutionized medicine. Although their mechanism of action is understood, the molecular bases for most of their side effects remain obscure. Here, we report that sulfamethoxazole and other sulfa drugs interfere with tetrahydrobiopterin biosynthesis through inhibition of sepiapterin reductase. Crystal structures of sepiapterin reductase with bound sulfa drugs reveal how structurally diverse sulfa drugs achieve specific inhibition of the enzyme. The effect of sulfa drugs on tetrahydrobiopterin-dependent neurotransmitter biosynthesis in cell-based assays provides a rationale for some of their central nervous system-related side effects, particularly in high-dose sulfamethoxazole therapy of Pneumocystis pneumonia. Our findings reveal an unexpected aspect of the pharmacology of sulfa drugs and might translate into their improved medical use.

Insights into ET(A) subtype selectivity of benzodiazepine endothelin receptor antagonists by 3D-QSAR approaches

ET(A) subtype selective antagonists constitute a novel and potentially important class of agents for the treatment of pulmonary hypertension, heart failure, and other pathological conditions. In this paper, 60 benzodiazepine derivatives displaying potent activities against ET(A) and ET(B) subtypes of endothelin receptor were selected to establish the 3D-QSAR models using CoMFA and CoMSIA approaches. These models show excellent internal predictability and consistency, external validation using test-set 19 compounds yields a good predictive power for antagonistic potency. Statistical parameters of models were obtained with CoMFA-ET(A) (q (2) = 0.787, r (2) = 0.935, r (2) ( pred ) = 0.901), CoMFA-ET(B) (q (2) = 0.842, r (2) = 0.984, r (2) ( pred ) = 0.941), CoMSIA-ET(A) (q (2) = 0.762, r (2) = 0.971, r (2) ( pred ) = 0.958) and CoMSIA-ET(B) (q (2) = 0.771, r (2) = 0.974, r (2) ( pred ) = 0.953) respectively. Field contour maps (CoMFA and CoMSIA) corresponding to the ET(A) and ET(B) subtypes reflects the characteristic similarities and differences between these types. The results of this paper provide valuable information to facilitate structural modifications of the title compounds to increase the inhibitory potency and subtype selectivity of endothelin receptor.

Tumor-evoked sensitization of C nociceptors: a role for endothelin

Primary and metastatic cancers that effect bone are frequently associated with pain. Sensitization of primary afferent C nociceptors innervating tissue near the tumor likely contributes to the chronic pain and hyperalgesia accompanying this condition. This study focused on the role of the endogenous peptide endothelin-1 (ET-1) as a potential peripheral algogen implicated in the process of cancer pain. Electrophysiological response properties, including ongoing activity and responses evoked by heat stimuli, of C nociceptors were recorded in vivo from the tibial nerve in anesthetized control mice and mice exhibiting mechanical hyperalgesia following implantation of fibrosarcoma cells into and around the calcaneus bone. ET-1 (100 microM) injected into the receptive fields of C nociceptors innervating the plantar surface of the hind paw evoked an increase in ongoing activity in both control and tumor-bearing mice. Moreover, the selective ETA receptor antagonist, BQ-123 (3 mM), attenuated tumor-evoked ongoing activity in tumor-bearing mice. Whereas ET-1 produced sensitization of C nociceptors to heat stimuli in control mice, C nociceptors in tumor-bearing mice were sensitized to heat, and their responses were not further increased by ET-1. Importantly, administration of BQ-123 attenuated tumor-evoked sensitization of C nociceptors to heat. We conclude that ET-1 at the tumor site contributes to tumor-evoked excitation and sensitization of C nociceptors through an ETA receptor mediated mechanism.

The endothelin system as a therapeutic target in cardiovascular disease: great expectations or bleak house?

There is considerable evidence that the potent vasoconstrictor endothelin-1 (ET-1) contributes to the pathogenesis of a variety of cardiovascular diseases. As such, pharmacological manipulation of the ET system might represent a promising therapeutic goal. Many clinical trials have assessed the potential of ET receptor antagonists in cardiovascular disease, the most positive of which have resulted in the licensing of the mixed ET receptor antagonist bosentan, and the selective ET(A) receptor antagonists, sitaxsentan and ambrisentan, for the treatment of pulmonary arterial hypertension (PAH). In contrast, despite encouraging data from in vitro and animal studies, outcomes in human heart failure have been disappointing, perhaps illustrating the risk of extrapolating preclinical work to man. Many further potential applications of these compounds, including resistant hypertension, chronic kidney disease, connective tissue disease and sub-arachnoid haemorrhage are currently being investigated in the clinic. Furthermore, experience from previous studies should enable improved trial design and scope remains for development of improved compounds and alternative therapeutic strategies. Although ET-converting enzyme inhibitors may represent one such alternative, there have been relatively few suitable compounds developed, and consequently, clinical experience with these agents remains extremely limited. Recent advances, together with an increased understanding of the biology of the ET system provided by improved experimental tools (including cell-specific transgenic deletion of ET receptors), should allow further targeting of clinical trials to diseases in which ET is involved and allow the therapeutic potential for targeting the ET system in cardiovascular disease to be fully realized.

Chemically programmed antibodies: endothelin receptor targeting CovX-Bodies

Aryl sulfonamide-based endothelin antagonists were synthesized and covalently linked to the reactive lysine of the m38C2 antibody to create a series of CovX-Bodies. These chemically programmed antibodies behaved as potent endothelin receptor antagonists in vitro and had antitumor efficacy in a prostate cancer xenograft model which, on a molar basis, far exceeded the activity of the parent small molecule.

Endothelin receptor antagonists

Endothelin receptor antagonists (ERAs) have been developed to block the effects of endothelin-1 (ET-1) in a variety of cardiovascular conditions. ET-1 is a powerful vasoconstrictor with mitogenic or co-mitogenic properties, which acts through the stimulation of 2 subtypes of receptors [endothelin receptor subtype A (ETA) and endothelin receptor subtype B (ETB) receptors]. Endogenous ET-1 is involved in a variety of conditions including systemic and pulmonary hypertension (PH), congestive heart failure (CHF), vascular remodeling (restenosis, atherosclerosis), renal failure, cancer, and cerebrovascular disease. The first dual ETA/ETB receptor blocker, bosentan, has already been approved by the Food and Drug Administration for the treatment of pulmonary arterial hypertension (PAH). Trials of endothelin receptor antagonists in heart failure have been completed with mixed results so far. Studies are ongoing on the effects of selective ETA antagonists or dual ETA/ETB antagonists in lung fibrosis, cancer, and subarachnoid hemorrhage. While non-peptidic ET-1 receptor antagonists suitable for oral intake with excellent bioavailability have become available, proven efficacy is limited to pulmonary hypertension, but it is possible that these agents might find a place in the treatment of several cardiovascular and non-cardiovascular diseases in the coming future.

Selective optimization of side activities: the SOSA approach

Selective optimization of side activities of drug molecules (the SOSA approach) is an intelligent and potentially more efficient strategy than HTS for the generation of new biological activities. Only a limited number of highly diverse drug molecules are screened, for which bioavailability and toxicity studies have already been performed and efficacy in humans has been confirmed. Once the screening has generated a hit it will be used as the starting point for a drug discovery program. Using traditional medicinal chemistry as well as parallel synthesis, the initial 'side activity' is transformed into the 'main activity' and, conversely, the initial 'main activity' is significantly reduced or abolished. This strategy has a high probability of yielding safe, bioavailable, original and patentable analogues.

Characterization of the in vitro atropisomeric interconversion rates of an endothelin A antagonist by enantioselective liquid chromatography

Substituted biphenyl I (BMS-207940), a selective antagonist of the endothelin A (ETA) receptor, has been proposed for the treatment of congestive heart failure. The structure of I possesses a stereogenic axis due to the hindered rotation about the biphenyl bond in the presence of its large ortho-substituents. As a result, I exhibits atropisomerism in which two nonplanar, axially enantiomers exist, which will be generically referred to as isomers A and B. Within the pharmaceutical industry, both from a scientific and regulatory point of view, characterization of enantiomeric drugs has become an important step in the development process. To investigate the configurational stability of I atropisomers, normal phase enantiomeric LC with tandem UV and laser polarimetric detection was used under pseudo-physiological conditions: first in a simple aqueous medium at 37 degrees C, and then in human serum at 37 degrees C. Kinetic studies indicated that the half-life of I enantiomerization in an aqueous medium at 37 degrees C was ca. 15 h. Enantiomerization of I atropisomers was greatly accelerated in the presence of human serum and human serum albumin, and the rate of enantiomerization depended on the concentration of I. The sera-concentration-dependent enantiomerization behavior of I strongly suggests a restricted site-specific substrate/I interaction mechanism. It was therefore demonstrated that atropisomeric interconversion studies for the compound studied required consideration of temperature, presence of plasma proteins, and drug concentration to account for the kinetic data.

Dual Angiotensin II and Endothelin A Receptor Antagonists: Synthesis of 2‘-Substituted N-3-Isoxazolyl Biphenylsulfonamides with Improved Potency and Pharmacokinetics

In a previous report we demonstrated that merging together key structural elements present in an AT(1) receptor antagonist (1, irbesartan) with key structural elements in a biphenylsulfonamide ET(A) receptor antagonist (2) followed by additional optimization provided compound 3 as a dual-action receptor antagonist (DARA), which potently blocked both AT(1) and ET(A) receptors. Described herein are our efforts directed toward improving both the pharmacokinetic profile as well as the AT(1) and ET(A) receptor potency of 3. Our efforts centered on modifying the 2'-side chain of 3 and examining the isoxazolylsulfonamide moiety in 3. This effort resulted in the discovery of 7 as a highly potent second-generation DARA. Compound 7 also showed substantially improved pharmacokinetic properties compared to 3. In rats, DARA 7 reduced blood pressure elevations caused by intravenous infusion of Ang II or big ET-1 to a greater extent and with longer duration than DARA 3 or AT(1) or ET(A) receptor antagonists alone. Compound 7 clearly demonstrated superiority over irbesartan (an AT(1) receptor antagonist) in the normal SHR model of hypertension in a dose-dependent manner, demonstrating the synergy of AT(1) and ET(A) receptor blockade in a single molecule.

Potent and orally active ETA selective antagonists with 5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acid structures

The synthesis and structure-activity relationships of a series of 5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids are described. Our efforts have been focused on modification of the aryl ring at the 5-position and the alkyl substituent at the 2-position of the bottom 4-methoxyphenyl ring in an effort to develop orally available ET(A) selective antagonists with safer profiles in terms of the P-450 enzyme inhibitory activity. Incorporation of a hydroxymethyl group as an alkyl substituent in methylenedioxyphenyl and 6-dihydrobenzofuran derivatives led to the identification of orally bioavailable ET(A) selective antagonists 1f and 7f. These compounds also showed not only excellent binding affinity (IC(50) < 0.10nM, more than 800-fold selectivity for the ET(A) receptor over the ET(B) receptor) but also sufficient oral bioavailability, 48% and 56%, respectively, in rats. Furthermore, these compounds did not exhibit either competitive or mechanism-based inhibition of human cytochrome P450 enzymes.

Novel Dual Action AT1 and ETA Receptor Antagonists Reduce Blood Pressure in Experimental Hypertension

Angiotensin II and endothelin-1 activate their respective AT(1) and ET(A) receptors on vascular smooth muscle cells, producing vasoconstriction, and both peptides are implicated in the pathogenesis of essential hypertension. Angiotensin II potentiates the production of endothelin, and conversely endothelin augments the synthesis of angiotensin II. Both AT(1) and ET(A) receptor antagonists lower blood pressure in hypertensive patients; thus, a combination AT(1)/ET(A) receptor antagonist may have greater efficacy and broader utility compared with each drug alone. By rational drug design a biphenyl ET(A) receptor blocker was modified to acquire AT(1) receptor antagonism. These compounds (C and D) decreased Sar-Ile-Angiotensin II binding to AT(1) receptors and endothelin-1 binding to ET(A) receptors, and compound C inhibited angiotensin II- and endothelin-1-mediated Ca(2+) transients. In rats compounds C and D reduced blood pressure elevations caused by intravenous infusion of angiotensin II or big endothelin-1. Compound C decreased blood pressure in Na(+)-depleted spontaneously hypertensive rats and in rats with mineralocorticoid hypertension. Compound D was more efficacious than AT(1) receptor antagonists at reducing blood pressure in spontaneously hypertensive rats, and its superiority was likely due to its partial blockade of ET(A) receptors. Therefore compounds C and D are novel agents for treating a broad spectrum of patients with essential hypertension and other cardiovascular diseases.

Physiology and pathology of endothelin-1 in renal mesangium

Mesangial cells (MCs) play a central role in the physiology and pathophysiology of endothelin-1 (ET-1) in the kidney. MCs release ET-1 in response to a variety of factors, many of which are elevated in glomerular injury. MCs also express ET receptors, activation of which leads to a complex signaling cascade with resultant stimulation of MC hypertrophy, proliferation, contraction, and extracellular matrix accumulation. MC ET-1 interacts with other important regulatory factors, including arachidonate metabolites, nitric oxide, and angiotensin II. Excessive stimulation of ET-1 production by, and activity in, MC is likely of pathogenic importance in glomerular damage in the setting of diabetes, hypertension, and glomerulonephritis. The recent introduction of ET antagonists, and possibly ET-converting enzyme inhibitors, into the clinical arena establishes the potential for new therapies for those diseases characterized by increased MC ET-1 actions. This review will examine our present understanding of how ET-1 is involved in mesangial function in health and disease. In addition, we will discuss the status of clinical trials using ET antagonists, which have only been conducted in nonrenal disease, as a background for advocating their use in diseases characterized by excessive MC-derived ET-1.