Selective ET(A) antagonists. 5. Discovery and structure-activity relationships of phenoxyphenylacetic acid derivatives

Efficient Approach to Carbinol Derivatives through Palladium-Catalyzed Base-Free Addition of Aryltriolborates to Aldehydes

Palladium-catalyzed base-free addition of aryltriolborates to aldehydes has been developed, leading to a wide range of carbinol derivatives in good to excellent yields. The efficiency of this transformation was demonstrated by compatibility with a wide range of functional groups. The present synthetic route to carbinol derivatives could be readily scaled up to gram quantity without difficulty. Thus, this method represents a simple and practical procedure to access carbinol derivatives.

Mandelic acid derived ionic liquids: synthesis, toxicity and biodegradability

Novel ionic liquids have been synthesised directly from the renewable resource mandelic acid and evaluated for their antimicrobial activity and biodegradability.

Metal-free one-pot α-carboxylation of primary alcohols

An efficient metal-free procedure for the formal α-carboxylation of primary alcohols has been developed. The method involves a one-pot oxidation/Passerini/hydrolysis sequence and provides access to α-hydroxy acids bearing a broad range of functional groups. A minor modification to the reaction conditions extends the range of accessible products to α-hydroxy esters.

Practical catalytic asymmetric synthesis of diaryl-, aryl heteroaryl-, and diheteroarylmethanols

Enantioenriched diaryl-, aryl heteroaryl-, and diheteroarylmethanols exhibit important biological and medicinal properties. One-pot catalytic asymmetric syntheses of these compounds beginning from readily available aryl bromides are introduced. Thus, lithium-bromide exchange with commercially available aryl bromides and n-BuLi was followed by salt metathesis with ZnCl(2) to generate ArZnCl. A second equivalent of n-BuLi was added to form the mixed organozinc, ArZnBu. In the presence of enantioenriched amino alcohol-based catalysts, ArZnBu adds to aldehydes to afford essentially racemic diarylmethanols. The low enantioselectivities were attributed to a LiCl-promoted background reaction. To inhibit this background reaction, the chelating diamine TEEDA (tetraethylethylene diamine) was introduced prior to aldehyde addition. Under these conditions, enantioenriched diarylmethanols were obtained with >90% ee. Arylations of enals generated allylic alcohols with 81-90% ee. This procedure was unsuccessful, however, when applied to heteroaryl bromides, which was attributed to decomposition of the heteroaryl lithium under the salt metathesis conditions. To avoid this problem, the metathesis was conducted with EtZnCl, which enabled the salt metathesis to proceed at low temperatures. The resulting EtZn(Ar(Hetero)) intermediates (Ar(Hetero) = 2- and 3-thiophenyl, 2-benzothiophenyl, 3-furyl, and 5-indolyl) were successfully added to aldehydes and heteroaryl aldehydes with enantioselectivities between 81-99%. These are the first examples of catalytic and highly enantioselective syntheses of diheteroarylmethanols. In a similar fashion, ferrocenyl bromide was used to generate FcZnEt and the ferrocenyl group added to benzaldehyde and heteroaromatic aldehydes to form ferrocene-based ligand precursors in 86-95% yield with 96-98% ee. It was also found that the arylation and heteroarylation of enals could be followed by diastereoselective epoxidations to provide epoxy alcohols with high enantio- and diastereoselectivities in a one-pot procedure.

Preparation of 2-, 3-, 4- and 7-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans and their BLT1 and/or BLT2 inhibitory activities

Several 2-alkylcarbamoyl-1-alkylvinylbenzo[b]furans were designed to find a selective leukotriene B4 (LTB4) receptor antagonist. 2-(2-Alkylcarbamoyl-1-alkylvinyl)benzo[b]furans having a substituent group at the 3-position, 4-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans having a substituent group at the 3-position, and 7-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans and 3-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans were prepared and evaluated for LTB4 receptor (BLT1 and BLT2) inhibitory activities. (E)-3-Amino-4-[2-[2-(3,4-dimethoxyphenyl)ethylcarbamoyl]-1-methylvinyl]benzo[b]furan ((E)-17c) showed potent and selective inhibitory activity for BLT2. On the other hand, (E)-7-(2-diethylcarbamoyl-1-methylvinyl)benzo[b]furan ((E)-27a) showed potent inhibitory activity for both BLT1 and BLT2.

The Palladium-Catalyzed Addition of Aryl- and Heteroarylboronic Acids to Aldehydes

Reaction of aryl- or heteroarylboronic acids with aldehydes, in the presence of PdCl2 and P(1-Nap)3, afforded carbinol derivatives in good to excellent yields. The efficiency of this reaction was demonstrated by the compatibility with nitro, cyano, acetamido, acetoxy, acetyl, carboxyl, trifluoromethyl, fluoro, and chloro groups and the possibility of involving aliphatic aldehyde or hindered substrates. Moreover, the rigorous exclusion of air/moisture is not required in these transformations.

Synthesis and cytotoxic evaluation of C-9 oxidized podophyllotoxin derivatives

A series of podophyllotoxin and podophyllic aldehyde derivatives, lacking the lactone ring and oxidized at C-9 position, has been prepared. The functionalities considered at C-9 were carboxylic acids and several derivatives such as esters, amides, nitriles or anhydrides. The synthesized compounds were cytotoxic at the micromolar level, though less potent and selective than the parent compounds, revealing the influence of the C-9 electrophilic character on the potency and selectivity of these cyclolignans.

Synthesis and biological activities of novel furo[2,3,4-jk][2]benzazepin-4(3H)-one derivatives

A novel seven-membered lactam formation method has been established by intramolecular ring closure reaction of 4-bromo-(E)-3-[(2-alkylvinyl)carbonylamino]benzo[b]furans under Heck coupling conditions. A number of furo[2,3,4-jk][2]benzazepin-4(3H)-ones, tricyclicbenzo[b]furans, have been prepared by this method and evaluated for their leukotriene B(4) (LTB(4)) receptor and poly(ADP-ribose)polymerase-1 (PARP-1) inhibitory activities.

Synthesis, in vitro pharmacology and biodistribution studies of new PD 156707-derived ET(A) receptor radioligands

It is assumed that the regulation of cardiac endothelin (ET) receptor density is abnormal in heart diseases. From that perspective, an ET receptor radioligand is needed to assess ET receptor density in vivo. The nonpeptidyl ET(A) receptor antagonist PD 169390 was labelled with radioiodine to give a putative radioligand for SPECT. Labelling with [125I]iodide and [123I]iodide was accomplished with good to excellent radiochemical yields. The affinities of the nonradioactive reference and those of selected precursor compounds for ET(A) receptors were determined, using [125I]iodine labelled endothelin-1 with mouse ventricular membranes. All employed substances exhibited potent in vitro pharmacological characteristics with Ki values comparable to that of the lead compound PD 156707. Biodistribution studies and scintigraphic imaging experiments in mice, however, showed no significant uptake of the [123I] derivative in the heart.

Emerging drugs for renal failure

Renal failure involves a significant impairment of the essential functions of the kidney, which can be either acute with sudden and rapid onset (acute renal failure [ARF]) or chronic with gradual onset (chronic renal failure [CRF]). ARF, if detected early, may be halted or reversed, whereas CRF is generally irreversible. Without treatment or intervention, both forms of renal failure lead to end stage renal failure (ESRF) or end stage renal disease (ESRD), requiring renal replacement therapy (RRT) in the form of dialysis or renal transplantation for survival. However, provision of RRT requires expert teams working in specialised units, making therapy of patients with renal failure expensive; furthermore, RRT is complex, with its own complications. Although pharmacological interventions have shown promise in experimental models, these have not been as successful in the clinical setting (e.g., administration of atrial natriuretic peptide, low-dose dopamine). At present, drugs are administered during CRF to either reduce one of the many risk factors of CRF (e.g., angiotensin-converting enzyme inhibitors, statins) or to deal with the consequences of CRF (e.g., erythropoietin, calcitriol). Recent evidence suggests that some of these interventions may provide further direct beneficial effects via reduction of renal inflammation. Although these interventions have greatly improved the prospects for patients suffering ESRF, the development of novel drugs and therapies with which to reduce the consequences of renal failure and ESRD remain topics of great interest. This article reviews the therapies available for the prevention and management of renal failure in adults and describes, in detail, emerging drugs and novel interventions that may soon become available for the treatment or prevention of ESRF.

Nucleophilic displacement at benzhydryl centers: asymmetric synthesis of 1,1-diarylalkyl derivatives

[reaction: see text] Activation of substituted 1,1-diarylmethanols as their corresponding toluenesulfonates and subsequent displacement with a range of carbon, nitrogen, oxygen, and sulfur nucleophiles proceeds in 81-96% yield. Enantiomerically enriched diarylmethanols 8a-c were activated and displaced with pyridine acetate enolate with complete stereochemical inversion at carbon to yield 1,1-diarylalkyl derivatives 10a-c without loss of optical purity.

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.

Syntheses of 3-acetoacetylaminobenzo[b]furan derivatives having cysteinyl leukotriene 2 receptor antagonistic activity

Novel 3-acetoacetylaminobenzo[b]furan derivatives having a modified triene system at the 3-position were synthesized starting with 3-aminobenzo[b]furans. The enol isomers, 3-[(3-hydroxybut-2-enonyl)amino]benzo[b]furans (), of the 3-acetoacetylaminobenzo[b]furans were obtained as stable isomers owing to formation of a hydrogen bonding between the enol hydroxyl group and the amidocarbonyl group. The planarity of the C-2 substituent through the C-3 side chain suggested the existence of a modified conjugational triene system in the enol compound. Cysteinyl leukotriene 1 and 2 receptor antagonistic activities for these compounds were evaluated. 2-(4-Cyanobenzoyl or ethoxycarbonyl)-3-[(2-cyano-3-hydroxybut-2-enonyl)amino]benzo[b]furans (, ) were moderately active.

Asymmetric synthesis of a selective endothelin A receptor antagonist

An asymmetric synthesis of a selective endothelin A receptor antagonist 1b is described. Asymmetric conjugate addition of aryllithium derived from 18 to the chiral oxazoline 17 followed by hydrolysis afforded 15 in 96% ee via purification as (S)-(-)-1-phenylethylamine salt. Pd(OAc)(2)/dppf (1,1'-bis(diphenylphosphino)ferrocene) catalyzed carbonylation followed by chemoselective addition of aryllithium derived from 23 which gave ketone 24. Diastereoselective reduction of the ketone with catecholborane followed by concomitant activation of the resulting alcohol and cyclization gave the late intermediate 26. Introduction of amino moiety on the pyridine ring by imidoyl rearrangement followed by deprotection and purification by crystallization furnished the enantiomerically pure target molecule 1b in 8% overall yield from 16.

Practical asymmetric synthesis of a selective endothelin A receptor (ETA) antagonist

[structure: see text]. A practical, chromotography-free asymmetric synthesis was developed for the large scale preparation of an endothelin receptor antagonist 2. This synthesis includes a new efficient process for the preparation of 6-bromo-2,3-dihydrobenzofuran, a stereoselective conjugate addition of an aryllithium followed by stereospecific addition of the Grignard reagent of the top aryl bromide, and an aminophosphate-mediated sterospecific intramolecular enolate alkylation, which led to the formation of the five-membered ring bearing three contiguous asymmetric centers.

Effect of endothelin antagonists, including the novel ET(A) receptor antagonist LBL 031, on endothelin-1 and lipopolysaccharide-induced microvascular leakage in rat airways

1. The effect of the novel ET(A) receptor antagonist LBL 031 and other selective and mixed endothelin receptor antagonists on endothelin-1 (ET-1)-induced and lipopolysaccharide (LPS)-induced microvascular leakage was assessed in rat airways. 2. Intravenously administered ET-1 (1 nmole kg(-1)) or LPS (30 mg kg(-1)) caused a significant increase in microvascular leakage in rat airways when compared to vehicle treated animals. 3. Pre-treatment with the selective ET(A) receptor antagonists, LBL 031 or PD 156707, or the mixed ET(A/B) receptor antagonist, bosentan (each at 30 mg kg(-1)), reduced ET-1-induced leakage to baseline levels. ET-1-induced leakage was not reduced by pre-treatment with the ET(B) selective antagonist BQ 788 (3 mg kg(-1)). 4. Pre-treatment with the selective ET(A) receptor antagonist, LBL 031 (0.1 mg kg(-1)) or PD 156707 (10 mg kg(-1)), or the mixed ET(A/B) receptor antagonist, bosentan (30 mg kg(-1)), reduced LPS-induced leakage by 54, 48 and 59% respectively. LPS-induced leakage was not affected by pre-treatment with the ET(B) selective antagonist BQ 788 (3 mg kg(-1)). 5. The data suggests that ET-1-induced microvascular leakage in the rat airway is ET(A) receptor mediated and that part of the increase induced by LPS may be due to the actions of ET-1. Therefore, a potent ET(A) receptor selective antagonist, such as LBL 031, may provide a suitable treatment for inflammatory diseases of the airways, especially those involving LPS and having an exudative phase, such as the septic shock-induced adult respiratory distress syndrome.