Discovery of a new class of triazole based inhibitors of acetyl transferase KAT2A

We have recently developed a new synthetic methodology that provided both N-aryl-5-hydroxytriazoles and N-pyridine-4-alkyl triazoles. A selection of these products was carried through virtual screening towards targets that are contemporary and validated for drug discovery and development. This study determined a number of potential structure target dyads of which N-pyridinium-4-carboxylic-5-alkyl triazole displayed the highest score specificity towards KAT2A. Binding affinity tests of abovementioned triazole and related analogs towards KAT2A confirmed the predictions of the in-silico assay. Finally, we have run in vitro inhibition assays of selected triazoles towards KAT2A; the ensemble of binding and inhibition assays delivered pyridyl-triazoles carboxylates as the prototype of a new class of inhibitors of KAT2A.

Vinylogous Nitro-Haloform Reaction Enables Aromatic Amination

The first example of an aromatic haloform reaction is reported, defining a conceptually new haloform-type approach to the metal-free functionalization of arenes. We demonstrated that heteroarenes bearing a vinylogous nitromethane system, via the stage of a trichloromethane derivative, could undergo aromatic amination to produce N-functionalized arenes in quantitative yields and without the need for transition-metal catalysis. The haloform-type amination was implemented in the development of effective orthogonal N-protection strategies, establishing a new promising N-protecting reagent.

Preparation of Acidic 5-Hydroxy-1,2,3-triazoles via the Cycloaddition of Aryl Azides with β-Ketoesters

Herein, a high-yielding cycloaddition reaction of β-ketoesters and azides to provide 1,2,3-triazoles is described. The reactions employing 2-unsubstituted β-ketoesters were found to provide 5-methyl-1,2,3-triazoles, whereas 2-alkyl-substituted β-ketoesters provided 5-hydroxy-1,2,3-triazoles (shown to be relatively acidic) in high yields and as single regioisomers. Several novel compounds were reported and characterized including long-chain 5-hydroxy-1,2,3-triazoles potentially bioisosteric to hydroxamic acids.

Study of Ground State Interactions of Enantiopure Chiral Quaternary Ammonium Salts and Amides, Nitroalkanes, Nitroalkenes, Esters, Heterocycles, Ketones and Fluoroamides

Chiral phase‐transfer catalysis provides high level of enantiocontrol, however no experimental data showed the interaction of catalysts and substrates. ¹H NMR titration was carried out on Cinchona and Maruoka ammonium bromides vs. nitro, carbonyl, heterocycles, and N−F containing compounds. It was found that neutral organic species and quaternary ammonium salts interacted via an ensemble of catalyst ⁺N−C−H and (sp²)C−H, specific for each substrate studied. The correspondent BArF salts interacted with carbonyls via a diverse set of ⁺N−C−H and (sp²)C−H compared to bromides. This data suggests that BArF ammonium salts may display a different enantioselectivity profile. Although not providing quantitative data for the affinity constants, the data reported proofs that chiral ammonium salts coordinate with substrates, prior to transition state, through specific C−H positions in their structures, providing a new rational to rationalize the origin of enantioselectivity in their catalyses.

Structural Insights on Tiny Peptide Nucleic Acid (PNA) Analogues of miRNA-34a: An in silico and Experimental Integrated Approach

In the present work, structural features of the interaction between peptide nucleic acid (PNA)-based analogs of the tumor-suppressor microRNA-34a with both its binding sites on MYCN mRNA were investigated. In particular, the region from base 1 to 8 ("seed" region) of miR-34a was reproduced in the form of an 8-mer PNA fragment (tiny PNA), and binding to target 3'UTR MYCN mRNA, was studied by a seldom reported and detailed NMR characterization, providing evidence for the formation of anti-parallel duplexes with a well-organized structural core. The formation of PNA-3'UTR duplexes was also confirmed by Circular Dichroism, and their melting curves were measured by UV spectroscopy. Nevertheless, this study offered a valuable comparison between molecular dynamics predictions and experimental evidence, which showed great correlation. Preliminary uptake assays were carried out in Neuroblastoma Kelly cells, using short peptide conjugates as carriers and FITC fluorescent tag for subcellular localization. Moderate internalization was observed without the use of transfecting agents. The reported results corroborate the interest toward the design and development of chimeric PNA/RNA sequences as effective RNA-targeting agents.

First enantioselective synthesis of gingesulfonic acids and unequivocal determination of their absolute stereochemistry

Herein we report the first organocatalysed enantioselective synthesis of gingesulfonic acids and shogasulfonic acids via a mild and convenient aminothiourea-catalysed conjugate addition of bisulfite to the olefin moiety of α,β-unsaturated carbonyls-a technology previously reported by us. A series of optically active naturally occurring sulfonic acids are prepared in their natural and unnatural configurations, and their absolute configurations are unequivocally confirmed by single crystal X-ray diffractometry.

Sulphide as a leaving group: highly stereoselective bromination of alkyl phenyl sulphides

A conceptionally novel nucleophilic substitution approach to synthetically important alkyl bromides is presented. Using molecular bromine (Br2), readily available secondary benzyl and tertiary alkyl phenyl sulphides are converted into the corresponding bromides under exceptionally mild, acid- and base-free reaction conditions. This simple transformation allows the isolation of elimination sensitive benzylic β-bromo carbonyl and nitrile compounds in mostly high yields and purities. Remarkably, protic functionalities such as acids and alcohols are tolerated. Enantioenriched benzylic β-sulphido esters, readily prepared by asymmetric sulpha-Michael addition, produce the corresponding inverted bromides with high stereoselectivities, approaching complete enantiospecificity at -40 °C. Significantly, the reported benzylic β-bromo esters can be stored without racemisation for prolonged periods at -20 °C. Their synthetic potential was demonstrated by the one-pot preparation of γ-azido alcohol (S)-5 in 90% ee. NMR studies revealed an initial formation of a sulphide bromine adduct, which in turn is in equilibrium with a postulated dibromosulphurane intermediate that undergoes C-Br bond formation.

A combined experimental and computational study on peptide nucleic acid (PNA) analogues of tumor suppressive miRNA-34a

MicroRNAs are a ubiquitous class of non-coding RNAs able to regulate gene expression in diverse biological processes. Widespread miRNAs deregulation was reported in numerous diseases including cancer, with several miRNAs playing oncogenic and/or tumor suppressive role by targeting multiple mRNAs simultaneously. Based on these findings, miRNAs have emerged as promising therapeutic tools for cancer treatment. Herein, for the first time, peptide nucleic acids (PNAs) were studied to develop a new class of molecules able to target 3'UTR on MYCN mRNA without a fully complementary base pairing sequence (as miRNAs). For our proof of concept study we have selected as a model the miRNA-34a, which acts as a tumor suppressor in a number of cancers including neuroblastoma. In particular, miRNA-34a is a direct regulator of MYCN oncogene, whose overexpression is a prominent biomarker for the highly aggressive neuroblastoma phenotype. The design and synthesis of three PNA-based oligomers of different length was described, and their interaction with two binding sites on the target MYCN mRNA was investigated by molecular dynamics simulation, and spectroscopic techniques (CD, UV). Intake assay and confocal microscopy of PNA sequences were also carried out in vitro on neuroblastoma Kelly cells. Despite the presence of multiple mismatches, the PNA/RNA hetero duplexes retain very interesting features in terms of stability, affinity as well as of cellular uptake.

Reaction of azides and enolisable aldehydes under the catalysis of organic bases and Cinchona based quaternary ammonium salts

This work describes a two-step sequence to prepare amides in moderate enantioselectivity from azides and enolisable aldehydes that proceeds under chiral phase transfer catalysis.

Enantioselective cyclopropanation of (Z)-3-substituted-2-(4-pyridyl)-acrylonitriles catalyzed by Cinchona ammonium salts

Cyclopropane esters holding two quaternary centres were prepared in high yields, complete diatereoselection and up to 83% ee, using a Chincona derived phase-tranfer catalyst.

Catalytic asymmetric conjugate addition of isocyanoacetate to (Z)-3-substituted-2-(4-pyridyl)-acrylonitrile, a reactive class of Michael acceptor

Un-substituted isocyanoacetate ethyl ester reacted with Michael acceptors 1a–m under the catalysis of Cinchona based quaternary ammonium salts providing imines 4a–m as a single diastereoisomer and in up to 94% ees.

Catalytic enantioselective addition of isocyanoacetate to 3-methyl-4-nitro-5-styrylisoxazoles under phase transfer catalysis conditions

The reaction between 3-methyl-4-nitro-5-styrylisoxazoles and ethyl isocyanoacetate proceeded under PTC to give enantioenriched monoadducts in high ee (up to 99%).

Insights on chiral, backbone modified peptide nucleic acids: Properties and biological activity

PNAs are emerging as useful synthetic devices targeting natural miRNAs. In particular 3 classes of structurally modified PNAs analogs are herein described, namely α, β and γ, which differ by their backbone modification. Their mode and binding affinity for natural nucleic acids and their use in medicinal chemistry as potential miRNA binders is discussed.

TIN-a combinatorial compound collection of synthetically feasible multicomponent synthesis products

The synthetic feasibility of any compound library used for virtual screening is critical to the drug discovery process. TIN, a recursive acronym for 'TIN Is Not commercial', is a virtual combinatorial database enumeration of diversity-orientated multicomponent syntheses (MCR). Using a 'one-pot' synthetic technique, 12 unique small molecule scaffolds were developed, predominantly styrylisoxazoles and bis-acetylenic ketones, with extensive derivatization potential. Importantly, the scaffolds were accessible in a single operation from commercially available sources containing R-groups which were then linked combinatorially. This resulted in a combinatorial database of over 28 million product structures, each of which is synthetically feasible. These structures can be accessed through a free Web-based 2D structure search engine or downloaded in SMILES, MOL2, and SDF formats. Subsets include a 10% diversity subset, a drug-like subset, and a lead-like subset that are also freely available for download and virtual screening ( http://mmg.rcsi.ie:8080/tin ).

Studies on the Generation of Unnatural C-Nucleosides with 1-Alkynyl-2-deoxy-d-riboses

1-alkynyl-2-deoxy-D-riboses 7 and 8 were independently synthesized and subsequently used to generate several novel C-nucleosides.

Generation of acylnitroso dienophiles: a study of metal catalysis

Four novel metal/amine catalysts efficiently converted Boc-NHOH to its acylnitroso species at 5 mol % catalyst loading. These reactions allowed the preparation of polyfunctional hetero Diels-Alder adducts in high yield and from truly commercially available materials.

Multicomponent Synthesis of 3-Indolepropionic Acids

A three-component one-pot procedure (3-MC) was developed to assemble 3-indolepropionic acids from commercially available materials. This new methodology affords the title compounds in high yields and without the use of chromatography. [reaction: see text].

Multicomponent Synthesis of 3-Heteroarylpropionic Acids

A four component one-pot procedure (4-MC) was developed to assemble 3-heteroarylpropionic acids from commercially available materials. This new methodology affords the title compounds in high yields and without the use of chromatography. [reaction: see text]

Multicomponent Synthesis of Spiroisoxazolines

A three-component one-pot procedure (3-MCR) was developed to assemble the spiroisoxazoline nucleus from commercially available materials. This new methodology affords the title compounds in high yields and without the use of chromatography.

Application of Bis-acetylenic Ketones in Synthesis: One-Pot Preparation of the 1,2,4-Triazepine and Oxatriazaindenone Cores

Bis-acetylenic ketones were used to generate two heterocyclic templates. Two efficient one-pot procedures for the preparation of the triazepine and oxa-triazaindenone cores are described.