N-(Heteroaryl)thiophene sulfonamides as angiotensin AT2 receptor ligands.

Two series of N-(heteroaryl)thiophene sulfonamides, encompassing either a methylene imidazole group or a tert-butylimidazolylacetyl group in the meta position of the benzene ring, have been synthesized. An AT2R selective ligand with a Ki of 42 nM was identified in the first series and in the second series, six AT2R selective ligands with significantly improved binding affinities and Ki values of <5 nM were discovered. The binding modes to AT2R were explored by docking calculations combined with molecular dynamics simulations. Although some of the high affinity ligands exhibited fair stability in human liver microsomes, comparable to that observed with C21 undergoing clinical trials, most ligands displayed a very low metabolic stability with t½ of less than 10 min in human liver microsomes. The most promising ligand, with an AT2R Ki value of 4.9 nM and with intermediate stability in human hepatocytes (t½ = 77 min) caused a concentration-dependent vasorelaxation of pre-contracted mouse aorta.

N-(Methyloxycarbonyl)thiophene sulfonamides as high affinity AT2 receptor ligands.

A series of meta-substituted acetophenone derivatives, encompassing N-(alkyloxycarbonyl)thiophene sulfonamide fragments have been synthesized. Several selective AT2 receptor ligands were identified, among those a tert-butylimidazole derivative (20) with a Ki of 9.3 nM, that demonstrates a high stability in human liver microsomes (t½ = 62 min) and in human hepatocytes (t½ = 194 min). This methyloxycarbonylthiophene sulfonamide is a 20-fold more potent binder to the AT2 receptor and is considerably more stable in human liver microsomes, than a previously reported and broadly studied structurally related AT2R prototype antagonist 3 (C38). Ligand 20 acts as an AT2R agonist and caused an AT2R mediated concentration-dependent vasorelaxation of pre-contracted mouse aorta. Furthermore, in contrast to imidazole derivative C38, the tert-butylimidazole derivative 20 is a poor inhibitor of CYP3A4, CYP2D6 and CYP2C9. It is demonstrated herein that smaller alkyloxycarbonyl groups make the ligands in this series of AT2R selective compounds less prone to degradation and that a high AT2 receptor affinity can be retained after truncation of the alkyloxycarbonyl group. Binding modes of the most potent AT2R ligands were explored by docking calculations combined with molecular dynamics simulations.

Biological characterization of new inhibitors of microsomal PGE synthase-1 in preclinical models of inflammation and vascular tone.

BACKGROUND AND PURPOSE: Microsomal PGE synthase-1 (mPGES-1), the inducible synthase that catalyses the terminal step in PGE2 biosynthesis, is of high interest as therapeutic target to treat inflammation. Inhibition of mPGES-1 is suggested to be safer than traditional NSAIDs, and recent data demonstrate anti-constrictive effects on vascular tone, indicating new therapeutic opportunities. However, there is a lack of potent mPGES-1 inhibitors lacking interspecies differences for conducting in vivo studies in relevant preclinical disease models. EXPERIMENTAL APPROACH: Potency was determined based on the reduction of PGE2 formation in recombinant enzyme assays, cellular assay, human whole blood assay, and air pouch mouse model. Anti-inflammatory properties were assessed by acute paw swelling in a paw oedema rat model. Effect on vascular tone was determined with human ex vivo wire myography. KEY RESULTS: We report five new mPGES-1 inhibitors (named 934, 117, 118, 322, and 323) that selectively inhibit recombinant human and rat mPGES-1 with IC50 values of 10-29 and 67-250 nM respectively. The compounds inhibited PGE2 production in a cellular assay (IC50 values 0.15-0.82 µM) and in a human whole blood assay (IC50 values 3.3-8.7 µM). Moreover, the compounds blocked PGE2 formation in an air pouch mouse model and reduced acute paw swelling in a paw oedema rat model. Human ex vivo wire myography analysis showed reduced adrenergic vasoconstriction after incubation with the compounds. CONCLUSION AND IMPLICATIONS: These mPGES-1 inhibitors can be used as refined tools in further investigations of the role of mPGES-1 in inflammation and microvascular disease.

A Series of Analogues to the AT2R Prototype Antagonist C38 Allow Fine Tuning of the Previously Reported Antagonist Binding Mode.

We here report on our continued studies of ligands binding to the promising drug target angiotensin II type 2 receptor (AT2R). Two series of compounds were synthesized and investigated. The first series explored the effects of adding small substituents to the phenyl ring of the known selective nonpeptide AT2R antagonist C38, generating small but significant shifts in AT2R affinity. One compound in the first series was equipotent to C38 and showed similar kinetic solubility, and stability in both human and mouse liver microsomes. The second series was comprised of new bicyclic derivatives, amongst which one ligand exhibited a five-fold improved affinity to AT2R as compared to C38. The majority of the compounds in the second series, including the most potent ligand, were inferior to C38 with regard to stability in both human and mouse microsomes. In contrast to our previously reported findings, ligands with shorter carbamate alkyl chains only demonstrated slightly improved stability in microsomes. Based on data presented herein, a more adequate, tentative model of the binding modes of ligand analogues to the prototype AT2R antagonist C38 is proposed, as deduced from docking redefined by molecular dynamic simulations.

A convenient transesterification method for synthesis of AT2 receptor ligands with improved stability in human liver microsomes.

A series of AT2R ligands have been synthesized applying a quick, simple, and safe transesterification-type reaction whereby the sulfonyl carbamate alkyl tail of the selective AT2R antagonist C38 was varied. Furthermore, a limited number of compounds where acyl sulfonamides and sulfonyl ureas served as carboxylic acid bioisosteres were synthesized and evaluated. By reducing the size of the alkyl chain of the sulfonyl carbamates, ligands 7a and 7b were identified with significantly improved in vitro metabolic stability in both human and mouse liver microsomes as compared to C38 while retaining the AT2R binding affinity and AT2R/AT1R selectivity. Eight of the compounds synthesized exhibit an improved stability in human microsomes as compared to C38.

Characterization of a human and murine mPGES-1 inhibitor and comparison to mPGES-1 genetic deletion in mouse models of inflammation.

Microsomal prostaglandin E synthase-1 (mPGES-1) inhibition has been suggested as an alternative to cyclooxygenase (COX) inhibition in the treatment of pain and inflammation. We characterized a selective inhibitor of mPGES-1 activity (compound III) and studied its impact on the prostanoid profile in various models of inflammation. Compound III is a benzoimidazole, which has a submicromolar IC50 in both human and rat recombinant mPGES-1. In cellular assays, it reduced PGE2 production in A549 cells, mouse macrophages and blood, causing a shunt to the prostacyclin pathway in the former two systems. Lastly, we assayed compound III in the air pouch model to verify its impact on the prostanoid profile and compare it to the profile obtained in mPGES-1 k.o. mice. As opposed to mPGES-1 genetic deletion, which attenuated PGE2 production and caused a shunt to the thromboxane pathway, mPGES-1 inhibition with compound III reduced PGE2 production and tended to decrease the levels of other prostanoids.

One-pot, two-step, microwave-assisted palladium-catalyzed conversion of aryl alcohols to aryl fluorides via aryl nonaflates.

A convenient procedure for converting aryl alcohols to aryl fluorides via aryl nonafluorobutylsulfonates (ArONf) is presented. Moderate to good one-pot, two-step yields were achieved by this nonaflation and microwave-assisted, palladium-catalyzed fluorination sequence. The reductive elimination step was investigated by DFT calculations to compare fluorination with chlorination, proving a larger thermodynamic driving force for the aryl fluoride product. Finally, a key aryl fluoride intermediate for the synthesis of a potent HCV NS3 protease inhibitor was smoothly prepared with the novel protocol.

A facilitated approach to evaluate the inhibitor mode and potency of compounds targeting microsomal prostaglandin e synthase-1.

Microsomal prostaglandin E(2) synthase-1 (MPGES1) catalyzes the formation of prostaglandin E(2) from the endoperoxide prostaglandin H(2). MPGES1 expression is induced in inflammatory diseases, and this enzyme is regarded as a potential drug target. To aid in the drug discovery effort, a simple method for determination of inhibition mechanism and potency toward both prostaglandin H(2) and glutathione (GSH) has been developed. Using an assay with thiobarbituric acid-based detection, the inhibitory effects of six MPGES1 inhibitors were evaluated. The IC(50) values obtained at three substrate (S) concentrations ([S]K(M)) were used to estimate inhibition modality and inhibition constant values. This facilitated strategy is a useful and general screening method to evaluate the inhibitory effects of new drug compounds.

HIV-1 protease inhibitors with a transition-state mimic comprising a tertiary alcohol: improved antiviral activity in cells.

By a small modification in the core structure of the previously reported series of HIV-1 protease inhibitors that encompasses a tertiary alcohol as part of the transition-state mimicking scaffold, up to 56 times more potent compounds were obtained exhibiting EC(50) values down to 3 nM. Three of the inhibitors also displayed excellent activity against selected resistant isolates of HIV-1. The synthesis of 25 new and optically pure HIV-1 protease inhibitors is reported, along with methods for elongation of the inhibitor P1' side chain using microwave-accelerated, palladium-catalyzed cross-coupling reactions, the biological evaluation, and X-ray data obtained from one of the most potent analogues cocrystallized with both the wild type and the L63P, V82T, I84 V mutant of the HIV-1 protease.

A new structural theme in C2-symmetric HIV-1 protease inhibitors: ortho-substituted P1/P1' side chains.

In this report, the rapid syntheses of 24 novel C2-symmetric HIV-1 protease inhibitors are described. Two ortho-iodobenzyloxy containing C-terminal duplicated inhibitors served as starting materials for microwave-enhanced palladium(0)-catalyzed carbon-carbon bond forming reactions (Suzuki, Sonogashira, Heck, and Negishi). Highly potent inhibitors equipped with ortho-functionalized P1/P1' side chains as the structural theme were identified. Computational efforts were applied to study the binding mode of this class of inhibitors and to establish structure-activity relationships. The overall orientation of the inhibitors in the active site was reproduced by docking which suggested three possible conformations of the P1/P1' groups of which two seem more plausible.

Stereoselective synthesis of 3-aminoindan-1-ones and subsequent incorporation into HIV-1 protease inhibitors.

A new method for the stereoselective synthesis of 3-aminoindan-1-ones from triflates of salicylic sulfinyl imines and ethylene glycol vinyl ether has been developed. The reaction sequence starts with a regioselective Heck reaction followed by stereoselective Lewis acid mediated annulation. Acidic cleavage of the sulfinamides produced pure (R)- and (S)-3-aminoindan-1-ones, which were successfully isolated and incorporated into active HIV-1 protease inhibitors.

Microwave-enhanced and metal-catalyzed functionalizations of the 4-aryl-dihydropyrimidone template.

Progress in organometallic catalysis and recent advancements in the development of carbonylative reaction protocols without direct use of carbon monoxide have been utilized for efficient functionalizations of 4-aryl-dihydropyrimidone structures. The use of modern microwave technology enabled both high reaction rates and convenient handling. Examples of palladium-catalyzed cross-couplings, Heck reactions, amino- and alkoxycarbonylations, and direct N-amidations of 4-(bromophenyl)-dihydropyrimidones were performed. Further, the first N3-arylations of the dihydropyrimidone ring system were successfully completed using the copper-catalyzed Goldberg reaction. Altogether, these protocols provide new tools for rapid generation of novel and diverse dihydropyrimidone derivatives.

High-speed synthesis of potent C2-symmetric HIV-1 protease inhibitors by in-situ aminocarbonylations.

Two novel series of C2-symmetric HIV-1 protease inhibitors were synthesized by microwave-promoted, palladium-catalyzed aminocarbonylations of the o-iodo- and m-bromobenzyloxy P1/P1' substituted core structures. Molybdenum hexacarbonyl was used as a convenient solid source of carbon monoxide in these transformations. After the initial high-speed library generation, biological testing identified highly active HIV-1 protease inhibitors. Selected ortho- and meta-decorated inhibitors were subsequently resynthesized on a larger scale and retested for their affinity toward HIV-1 protease, showing micromolar to low nanomolar inhibition. The discovery of highly active inhibitors containing large phenyl amide ortho substituents in the P1/P1' positions indicates that larger groups than previously believed are tolerated in this part of the S1/S1' pocket.

Microwave-enhanced medicinal chemistry: a high-speed opportunity for convenient preparation of protease inhibitors.

The unique properties of microwave in situ heating offer unparalleled opportunities for medicinal chemists to accelerate lead optimization processes in early drug discovery. The technology is ideal for palladium-catalyzed alteration chemistry as it allows for complete control over reactions, with the use of non-inert conditions, providing high chemoselectivity and rapid feedback. To illustrate the advantages of this methodology, we describe our applications and approaches for the rapid synthesis of novel aspartyl protease inhibitors using dedicated microwave equipment. Biological results from chemical studies of the different side-chain positions of HIV-1 and malarial plasmepsin I and II protease inhibitors are summarized.

Increasing rates and scope of reactions: sluggish amines in microwave-heated aminocarbonylation reactions under air.

Commercially available molybdenum hexacarbonyl serves as a convenient and solid carbon monoxide source in palladium-catalyzed aminocarbonylations of aryl bromides and iodides. This improved microwave protocol, relying on DBU as base and THF as solvent, enables rapid couplings using otherwise sluggish anilines, tert-butylamine, and free amino acids. In addition, Cr(CO)(6) and W(CO)(6) were found to be useful alternative CO-releasing reagents. Altogether, 16 different aromatic amides were synthesized under air in 35-95% yield after only 15 min of controlled microwave irradiation.