CDP840. A prototype of a novel class of orally active anti-inflammatory phosphodiesterase 4 inhibitors

Novel Set of Diarylmethanes to Target Colorectal Cancer: Synthesis, In Vitro and In Silico Studies

Distinctive structural, chemical, and physical properties make the diarylmethane scaffold an essential constituent of many active biomolecules nowadays used in pharmaceutical, agrochemical, and material sciences. In this work, 33 novel diarylmethane molecules aiming to target colorectal cancer were designed. Two series of functionalized olefinic and aryloxy diarylmethanes were synthesized and chemically characterized. The synthetic strategy of olefinic diarylmethanes involved a McMurry cross-coupling reaction as key step and the synthesis of aryloxy diarylmethanes included an O-arylation step. A preliminarily screening in human colorectal cancer cells (HT-29 and HCT116) and murine primary fibroblasts (L929) allowed the selection, for more detailed analyses, of the three best candidates (10a, 10b and 12a) based on their high inhibition of cancer cell proliferation and non-toxic effects on murine fibroblasts (<100 µM). The anticancer potential of these diarylmethane compounds was then assessed using apoptotic (phospho-p38) and anti-apoptotic (phospho-ERK, phospho-Akt) cell survival signaling pathways, by analyzing the DNA fragmentation capacity, and through the caspase-3 and PARP cleavage pro-apoptotic markers. Compound 12a (2-(1-(4-methoxyphenyl)-2-(4-(trifluoromethyl)phenyl) vinyl) pyridine, Z isomer) was found to be the most active molecule. The binding mode to five biological targets (i.e., AKT, ERK-1 and ERK-2, PARP, and caspase-3) was explored using molecular modeling, and AKT was identified as the most interesting target. Finally, compounds 10a, 10b and 12a were predicted to have appropriate drug-likeness and good Absorption, Distribution, Metabolism and Excretion (ADME) profiles.

Palladium-catalyzed asymmetric allylic 4-pyridinylation via electroreductive substitution reaction

The enantioselective pyridinylation is important for providing chiral compounds bearing heterocycles of pharmaceutical interests. 4-CN-pyrinde is extensively applied in the radical pyridinylation reaction, however, its' enantioselective application is highly challenging. To achieve this goal, we propose an electrochemical catalytic activation of 4-CN-pyridine with a chiral transition metal complex instead of direct cathodic reduction. The chiral catalyst acts as the electron mediator and the transition metal catalysis in turn. The radical species from 4-CN-pyridine is captured via radical rebound by chiral catalyst, and undergoes enantioselective pyridinylation reaction. Here, we show the first method for catalytic asymmetric allylic 4-pyridinylation reactions using 4-CN-pyridine under electrochemical conditions.

Unified synthesis of multiply arylated alkanes by catalytic deoxygenative transformation of diarylketones

A deoxygenative transformation of diarylketones leading to multiply arylated alkanes was developed. Diarylketones were reacted with diphenylphosphine oxide resulting in a phospha-Brook rearrangement, followed by palladium-catalyzed cross-couplings or a Friedel-Crafts type alkylation to afford the corresponding multiply arylated alkanes. A variety of diarylketones can be converted to multiply arylated alkanes such as diarylmethanes, tetraarylethanes, and triarylmethanes by reduction, dimerization, and arylation in one pot. Furthermore, a one-pot conversion from arylcarboxylic acids to diarylmethanes and tetraarylethanes, and a synthesis of tetraarylmethane and triphenylethane using sequential coupling reactions are also presented.

Pegylated triarylmethanes: Synthesis, antimicrobial activity, anti-proliferative behavior and in silico studies

We describe herein the synthesis, characterization and biological studies of novel PEGylated triarylmethanes. Non-symmetrical and symmetrical triarylmethanes series have been synthesized by Friedel-Crafts hydroxyalkylation or directly from bisacodyl respectively followed by a functionalization with PEG fragments in order to increase bioavailability and biological effectiveness. The antimicrobial activity was investigated against Gram-positive and Gram-negative foodborne pathogens and against Candida albicans, an opportunistic pathogenic yeast. The anti-biocidal activity was also studied using Staphylococcus aureus as a reference bacterium. Almost all PEGylated molecules displayed an antifungal activity comparable with fusidic acid with MIC values ranging from 6.25 to 50 μg/mL. Compounds also revealed a promising antibiofilm activity with biofilm eradication percentages values above 80% for the best molecules (compounds 4d and 7). Compounds 7 and 8b showed a modest antiproliferative activity against human colorectal cancer cell lines HT-29. Finally, in silico molecular docking studies revealed DHFR and DNA gyrase B as potential anti-bacterial targets and in silico predictions of ADME suggested adequate drug-likeness profiles for the synthetized triarylmethanes.

Cyclic nucleotide phosphodiesterases: New targets in the metabolic syndrome?

Metabolic diseases have a tremendous impact on human morbidity and mortality. Numerous targets regulating adenosine monophosphate kinase (AMPK) have been identified for treating the metabolic syndrome (MetS), and many compounds are being used or developed to increase AMPK activity. In parallel, the cyclic nucleotide phosphodiesterase families (PDEs) have emerged as new therapeutic targets in cardiovascular diseases, as well as in non-resolved pathologies. Since some PDE subfamilies inactivate cAMP into 5'-AMP, while the beneficial effects in MetS are related to 5'-AMP-dependent activation of AMPK, an analysis of the various controversial relationships between PDEs and AMPK in MetS appears interesting. The present review will describe the various PDE families, AMPK and molecular mechanisms in the MetS and discuss the PDEs/PDE modulators related to the tissues involved, thus supporting the discovery of original molecules and the design of new therapeutic approaches in MetS.

K2S2O8-HFIP synergistically promoted para-selective sp3 C-H bond diarylation of glycine esters

A metal-free K₂S₂O₈-HFIP synergistically promoted double Friedel-Crafts alkylation between a glycine derivative and N-substituted aniline was developed to efficiently synthesize diarylmethane derivatives with high para-selectivity. The reaction proceeded smoothly in the absence of any metal and ligand, and exhibited a good tolerance of functional groups.

V. K, Hari K, Kaliyamoorthy A. Base-promoted 1,6-conjugate addition of alkylazaarenes to para-quinone methides

1,1,2-Triarylethanes embedded with an azaarene unit were prepared in a single step at ambient temperature via the sodium hexamethyldisilazide mediated 1,6-conjugate addition of unactivated alkylazaarenes on para-quinone methides (p-QMs).

Nickel-Catalyzed Asymmetric Reductive Diarylation of Vinylarenes

A nickel-catalyzed asymmetric diarylation reaction of vinylarenes enables the preparation of chiral α,α,β-triarylated ethane scaffolds, which exist in a number of biologically active molecules. The use of reducing conditions with aryl bromides as coupling partners obviates the need for stoichiometric organometallic reagents and tolerates a broad range of functional groups. The application of an N-oxyl radical as a ligand to a nickel catalyst represents a novel approach to facilitate nickel-catalyzed cross-coupling reactions.

Potassium-Zincate-Catalyzed Benzylic C-H Bond Addition of Diarylmethanes to Styrenes

Direct functionalization of the benzylic C-H bond of diarylmethanes is an important strategy for the synthesis of diarylmethine-containing compounds. However, the methods developed to date for this purpose require a stoichiometric amount (usually more) of either a strong base or an oxidant. Reported here is the first catalytic benzylic C-H bond addition of diarylmethanes to styrenes and conjugated dienes. A potassium zincate complex, generated from potassium benzyl and zinc amide, acts as a catalyst and displays good activity and chemoselectivity. Considering the atom economy of the reaction and the ready availability of the catalyst, this reaction constitutes a practical, efficient method for diarylalkane synthesis.

Ruthenium(II)-Catalyzed C-H (Hetero)Arylation of Alkenylic 1,n-Diazines (n = 2, 3, and 4): Scope, Mechanism, and Application in Tandem Hydrogenations

A general ruthenium(II)-catalyzed methodology enabling the (hetero)arylation of alkenylic C-H bonds utilizing a series of synthetically appealing diazines as directing groups is presented. Despite the presence of additional nitrogen lone pairs remote from the C-H bond activation site, which could eventually poison the catalyst, the reaction times are short (3 h), thus being suitable for selective double C-H bond arylation. Mixtures of E:Z isomeric products were observed in some cases, which were further hydrogenated in a tandem manner in the presence of the remaining ruthenium catalyst from the first step, representing an alternative approach to more difficult C(sp³)-H bond functionalization. According to mechanistic studies, the unexpected E:Z product formation seems to occur by thermal C═C bond isomerization after the reductive elimination step.

Assessing protein-ligand binding modes with computational tools: the case of PDE4B

In a first step in the discovery of novel potent inhibitor structures for the PDE4B family with limited side effects, we present a protocol to rank newly designed molecules through the estimation of their IC[Formula: see text] values. Our protocol is based on reproducing the linear relationship between the logarithm of experimental IC[Formula: see text] values [[Formula: see text](IC[Formula: see text])] and their calculated binding free energies ([Formula: see text]). From 13 known PDE4B inhibitors, we show here that (1) binding free energies obtained after a docking process by AutoDock are not accurate enough to reproduce this linear relationship; (2) MM-GB/SA post-processing of molecular dynamics (MD) trajectories of the top ranked AutoDock pose improves the linear relationship; (3) by taking into account all representative structures obtained by AutoDock and by averaging MM-GB/SA computations on a series of 40 independent MD trajectories, a linear relationship between [Formula: see text](IC[Formula: see text]) and the lowest [Formula: see text] is achieved with [Formula: see text].

Catalyst free synthesis of α-fluoro-β-hydroxy ketones/α-fluoro-ynols via electrophilic fluorination of tertiary propargyl alcohols using Selectfluor™ (F-TEDA-BF4)

A facile access to α-fluoro-β-hydroxyketones via electrophilic fluorination.

Development and Analysis of a Pd(0)-Catalyzed Enantioselective 1,1-Diarylation of Acrylates Enabled by Chiral Anion Phase Transfer

Enantioselective 1,1-diarylation of terminal alkenes enabled by the combination of Pd catalysis with a chiral anion phase transfer (CAPT) strategy is reported herein. The reaction of substituted benzyl acrylates with aryldiazonium salts and arylboronic acids gave the corresponding 3,3-diarylpropanoates in moderate to good yields with high enantioselectivies (up to 98:2 er). Substituents on the benzyl acrylate and CAPT catalyst significantly affect the enantioselectivity, and multidimensional parametrization identified correlations suggesting structural origins for the high stereocontrol.

Iterative protecting group-free cross-coupling leading to chiral multiply arylated structures

The Suzuki–Miyaura cross-coupling is one of the most often utilized reactions in the synthesis of pharmaceutical compounds and conjugated materials. In its most common form, the reaction joins two sp²-functionalized carbon atoms to make a biaryl or diene/polyene unit. These substructures are widely found in natural products and small molecules and thus the Suzuki–Miyaura cross-coupling has been proposed as the key reaction for the automated assembly of such molecules, using protecting group chemistry to affect iterative coupling. We present herein, a significant advance in this approach, in which multiply functionalized cross-coupling partners can be employed in iterative coupling without the use of protecting groups. To accomplish this, the orthogonal reactivity of different boron substituents towards the boron-to-palladium transmetalation reaction is exploited. The approach is illustrated in the preparation of chiral enantioenriched compounds, which are known to be privileged structures in active pharmaceutical compounds.

The Suzuki-Miyaura cross coupling is widely used in industrial and academic settings for the formation of carbon-carbon bonds. Here, the authors report a procedure whereby a molecule with multiple reactive carbon-boron bonds can undergo sequential, selective Suzuki-Miyaura reactions without the need for protecting groups.

Copper-catalyzed asymmetric three-component borylstannation: enantioselective formation of C-Sn bond

In summary, a first copper-catalyzed synthesis of α-aryl-β-borylstannane compounds was accomplished through three-component borylstannation of aryl-substituted alkenes. In the exploration of an asymmetric variant, chiral sulfinylphosphine ligands proved advantageous in controlling stereochemistry of B-Cu addition and in promoting transmetalation of enantioenriched alkyl-Cu species. The stereochemical outcome supported a sequential syn-borylcupration and configuration-retentive transmetalation mechanism. Moreover, α-chiral β-borylstannanes were easily transformed into a diverse array of secondary alkylstannanes and triarylethane with high enantiomeric purity. The applications of chiral sulfinylphosphine ligands to other tandem Cu-B addition reactions are currently under investigation in our group.

Arylboration of alkenes by cooperative palladium/copper catalysis

Arylboration of vinylarenes and methyl crotonate with aryl halides and bis(pinacolato)diboron by cooperative Pd/Cu catalysis has been developed, giving 2-boryl-1,1-diarylethanes and an α-aryl-β-boryl ester in a regioselective manner. The reaction is compatible with a variety of functionalities and amenable to be scaled-up to a gram scale with no detriment to the yield. A short synthesis of the biologically active compound CDP840 was performed using the present reaction as a key step.

1,4-Additions of arylboron, -silicon, and -bismuth compounds to α,β-unsaturated carbonyl compounds catalyzed by dicationic palladium(II) complexes

An enantioselective synthesis of cyclic and acyclic β-aryl ketone and aldehydes via Pd(II)-catalyzed 1,4-addition of Ar-m [m = B(OH)2, BF3K, Si(OMe)3, SiF3, BiAr2] to α,β-unsaturated ketones or aldehydes is described. The catalytic cycle involves transmetallation between Ar-m and Pd complexes as a key process, the mechanism of which is discussed on the basis of characterization of the transmetallation intermediate and electronic effect of the substituents. The enantioselection mechanism and efficiency of a chiraphos ligand for structurally planar α,β-unsaturated ketones are discussed on the basis of the X-ray structure of the catalyst and results of density functional theory (DFT) computational studies on the model of coordination of the substrates to the phenylpalladium(II)/(S,S)-chiraphos intermediate.

ABCD of the phosphodiesterase family: interaction and differential activity in COPD

Phosphodiesterases (PDEs) are important enzymes that hydrolyze the cyclic nucleotides adenosine 3'5'-cyclic monophosphate (cAMP) and guanosine 3'5'-cyclic monophosphate (cGMP) to their inactive 5' monophosphates. They are highly conserved across species and as well as their role in signal termination, they also have a vital role in intra-cellular localization of cyclic nucleotide signaling and integration of the cyclic nucleotide pathways with other signaling pathways. Because of their pivotal role in intracellular signaling, they are now of considerable interest as therapeutic targets in a wide variety diseases, including COPD where PDE inhibitors may have bronchodilator, anti-inflammatory and pulmonary vasodilator actions. This review examines the diversity and cellular localization of the isoforms of PDE, the known and speculative relevance of this to the treatment of COPD, and the range of PDE inhibitors in development together with a discussion of their possible role in treating COPD.

Synthesis of pyrrolo[2,3-d]pyridazinones as potent, subtype selective PDE4 inhibitors

A series of pyrrolo [2,3-d]pyridazinones was synthesized and tested for their inhibitory activity on PDE4 subtypes A, B and D and selectivity toward Rolipram high affinity binding site (HARBS). New agents with interesting profile were reported; in particular compound 9e showed a good PDE4 subtype selectivity, being 8 times more potent (IC50 = 0.32 microM) for PDE4B (anti-inflammatory) than for PDE4D (IC50 = 2.5 microM), generally considered the subtype responsible for emesis. Moreover the ratio HARBS/PDE4B was particularly favourable for 9e (147), suggesting that the best arranged groups around the pyrrolopyridazinone core are an isopropyl at position-1, an ethoxycarbonyl at position-2, together with an ethyl group at position-6. For compounds 8 and 15a the ability to inhibit TNFalpha production in PBMC was evaluated and the results are consistent with their PDE4 inhibitory activity.

Asymmetric Synthesis of Functionalized Diarylmethanols Catalyzed by a New γ-Amino Thiol

[reaction: see text] A mild asymmetric arylation of aromatic aldehydes catalyzed by gamma-amino thiol 5 gave the corresponding diarylmethanols with 95 to >99.5% ee.

Cyclic nucleotide phosphodiesterase (PDE) superfamily: a new target for the development of specific therapeutic agents

Cyclic nucleotide phosphodiesterases (PDEs), which are ubiquitously distributed in mammalian tissues, play a major role in cell signaling by hydrolyzing cAMP and cGMP. Due to their diversity, which allows specific distribution at cellular and subcellular levels, PDEs can selectively regulate various cellular functions. Their critical role in intracellular signaling has recently designated them as new therapeutic targets for inflammation. The PDE superfamily represents 11 gene families (PDE1 to PDE11). Each family encompasses 1 to 4 distinct genes, to give more than 20 genes in mammals encoding the more than 50 different PDE proteins probably produced in mammalian cells. Although PDE1 to PDE6 were the first well-characterized isoforms because of their predominance in various tissues and cells, their specific contribution to tissue function and their regulation in pathophysiology remain open research fields. This concerns particularly the newly discovered families, PDE7 to PDE11, for which roles are not yet established. In many pathologies, such as inflammation, neurodegeneration, and cancer, alterations in intracellular signaling related to PDE deregulation may explain the difficulties observed in the prevention and treatment of these pathologies. By inhibiting specifically the up-regulated PDE isozyme(s) with newly synthesized potent and isozyme-selective PDE inhibitors, it may be potentially possible to restore normal intracellular signaling selectively, providing therapy with reduced adverse effects.

Practical Asymmetric Synthesis of a Potent PDE4 Inhibitor via Stereoselective Enolate Alkylation of a Chiral Aryl−Heteroaryl Secondary Tosylate

A practical, chromatography-free catalytic asymmetric synthesis of a potent and selective PDE4 inhibitor (L-869,298, 1) is described. Catalytic asymmetric hydrogenation of thiazole ketone 5a afforded the corresponding alcohol 3b in excellent enantioselectivity (up to 99.4% ee). Activation of alcohol 3b via formation of the corresponding p-toluenesulfonate followed by an unprecedented displacement with the lithium enolate of ethyl 3-pyridylacetate N-oxide 4a generated the required chiral trisubstituted methane. The displacement reaction proceeded with inversion of configuration and without loss of optical purity. Conversion of esters 2b to 1 was accomplished via a one-pot deprotection, saponification, and decarboxylation sequence in excellent overall yield.

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.

Substituted 2-pyridinemethanol derivatives as potent and selective phosphodiesterase-4 inhibitors

The synthesis and the phosphodiesterase-4 (PDE4) inhibitory activity of 2-pyridinemethanol derivatives is described. The evaluation of the structure-activity relationship (SAR) in this series of novel PDE4 inhibitors led to the identification of compound 9 which exhibits excellent in vitro activity, desirable pharmacokinetic parameters and good efficacy in animal models of bronchoconstriction.

Deletion of phosphodiesterase 4D in mice shortens alpha(2)-adrenoceptor-mediated anesthesia, a behavioral correlate of emesis

A combination of pharmacological and genetic approaches was used to determine the role of type 4 cAMP-specific cyclic nucleotide phosphodiesterase 4 (PDE4) in reversing alpha(2)-adrenoceptor-mediated anesthesia, a behavioral correlate of emesis in non-vomiting species. Among the family-specific PDE inhibitors, PDE4 inhibitors reduced the duration of xylazine/ketamine-induced anesthesia in mice, with no effect on pentobarbital-induced anesthesia. The rank order of the PDE4 inhibitors tested was 6-(4-pyridylmethyl)-8-(3-nitrophenyl)quinoline (PMNPQ) > (R)-rolipram > (S)-rolipram >> (R)-N-[4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl]N'-ethylurea (CT-2450). The specific roles of PDE4B and PDE4D in this model were studied using mice deficient in either subtype. PDE4D-deficient mice, but not PDE4B-deficient mice, had a shorter sleeping time than their wild-type littermates under xylazine/ketamine-induced anesthesia, but not under that induced with pentobarbital. Concomitantly, rolipram-sensitive PDE activity in the brain stem was decreased only in PDE4D-deficient mice compared with their wild-type littermates. While PMNPQ significantly reduced the xylazine/ketamine-induced anesthesia period in wild-type mice and in PDE4B-null mice, it had no effect in PDE4D-deficient mice. These findings strongly support the hypothesis that inhibition of PDE4D is pivotal to the anesthesia-reversing effect of PMNPQ and is likely responsible for emesis induced by PDE4 inhibitors.