Access to novel imidazo[1,5-a]pyrazine scaffolds by the combined use of a three-component reaction and a base-assisted intramolecular cyclization

A novel and practical two-step approach to an intriguing class of imidazo[1,5-a]pyrazines with exocyclic C=X (X = CH2, O) bonds is described. The process utilizes a sequential three-component reaction of propargyl amine or aminoester, 1,2-diaza-1,3-dienes and isothiocyanates to furnish functionalized 2-thiohydantoins which are transformed into thiohydantoin-fused tetrahydropyrazines by subsequent regioselective base-promoted cyclization.

Focused chemical libraries--design and enrichment: an example of protein-protein interaction chemical space

One of the many obstacles in the development of new drugs lies in the limited number of therapeutic targets and in the quality of screening collections of compounds. In this review, we present general strategies for building target-focused chemical libraries with a particular emphasis on protein-protein interactions (PPIs). We describe the chemical spaces spanned by nine commercially available PPI-focused libraries and compare them to our 2P2I3D academic library, dedicated to orthosteric PPI modulators. We show that although PPI-focused libraries have been designed using different strategies, they share common subspaces. PPI inhibitors are larger and more hydrophobic than standard drugs; however, an effort has been made to improve the drug-likeness of focused chemical libraries dedicated to this challenging class of targets.

Discovery of new heterocycles with activity against human neutrophile elastase based on a boron promoted one-pot assembly reaction

Herein we demonstrate for the first time that a boron promoted one-pot assembly reaction may be used to discover novel enzyme inhibitors. Inhibitors for HNE were simply assembled in excellent yields, high diastereoselectivities and IC50 up to 1.10 μM, based on components like salicylaldehyde, aryl boronic acids and amino acids. The combination of synthetic, biochemical, analytical and theoretical studies allowed the identification of the 4-methoxy or the 4-diethyl amino substituent of the salicylaldehyde as the most important recognition moiety and the imine alkylation, lactone ring opening as key events in the mechanism of inhibition.

Ruthenium-catalyzed direct C-3 oxidative olefination of imidazo[1,2-a]pyridines

Ruthenium-catalyzed regioselective C-3 oxidative olefination of imidazo[1,2-a]pyridines.

Solid phase synthesis of α-amino squaric acid-containing peptides

A new method has been developed for the synthesis of 3-(1-aminoalkyl)-4-hydroxycyclobut-3-ene-1,2-dione [(α-amino squaric acid (α-Asq)]-containing peptides using solid phase peptide synthesis according to an Fmoc protecting group strategy.

2P2I HUNTER: a tool for filtering orthosteric protein-protein interaction modulators via a dedicated support vector machine

Over the last 10 years, protein-protein interactions (PPIs) have shown increasing potential as new therapeutic targets. As a consequence, PPIs are today the most screened target class in high-throughput screening (HTS). The development of broad chemical libraries dedicated to these particular targets is essential; however, the chemical space associated with this 'high-hanging fruit' is still under debate. Here, we analyse the properties of 40 non-redundant small molecules present in the 2P2I database (http://2p2idb.cnrs-mrs.fr/) to define a general profile of orthosteric inhibitors and propose an original protocol to filter general screening libraries using a support vector machine (SVM) with 11 standard Dragon molecular descriptors. The filtering protocol has been validated using external datasets from PubChem BioAssay and results from in-house screening campaigns. This external blind validation demonstrated the ability of the SVM model to reduce the size of the filtered chemical library by eliminating up to 96% of the compounds as well as enhancing the proportion of active compounds by up to a factor of 8. We believe that the resulting chemical space identified in this paper will provide the scientific community with a concrete support to search for PPI inhibitors during HTS campaigns.

Hydrogen-bond landscapes, geometry and energetics of squaric acid and its mono- and dianions: a Cambridge Structural Database, IsoStar and computational study

As part of a programme of work to extend central-group coverage in the Cambridge Crystallographic Data Centre's (CCDC) IsoStar knowledge base of intermolecular interactions, we have studied the hydrogen-bonding abilities of squaric acid (H2SQ) and its mono- and dianions (HSQ(-) and SQ(2-)) using the Cambridge Structural Database (CSD) along with dispersion-corrected density functional theory (DFT-D) calculations for a range of hydrogen-bonded dimers. The -OH and -C=O groups of H2SQ, HSQ(-) and SQ(2-) are potent donors and acceptors, as indicated by their hydrogen-bond geometries in available crystal structures in the CSD, and by the attractive energies calculated for their dimers with acetone and methanol, which were used as model acceptors and donors. The two anions have sufficient examples in the CSD for their addition as new central groups in IsoStar. It is also shown that charge- and resonance-assisted hydrogen bonds involving H2SQ and HSQ(-) are similar in strength to those made by carboxylate COO(-) acceptors, while hydrogen bonds made by the dianion SQ(2-) are somewhat stronger. The study reinforces the value of squaric acid and its anions as cocrystal formers and their actual and potential importance as isosteric replacements for carboxylic acid and carboxylate functions.

Heterogenized cobalt oxide catalysts for nitroarene reduction by pyrolysis of molecularly defined complexes

Molecularly well-defined homogeneous catalysts are known for a wide variety of chemical transformations. The effect of small changes in molecular structure can be studied in detail and used to optimize many processes. However, many industrial processes require heterogeneous catalysts because of their stability, ease of separation and recyclability, but these are more difficult to control on a molecular level. Here, we describe the conversion of homogeneous cobalt complexes into heterogeneous cobalt oxide catalysts via immobilization and pyrolysis on activated carbon. The catalysts thus produced are useful for the industrially important reduction of nitroarenes to anilines. The ligand indirectly controls the selectivity and activity of the recyclable catalyst and catalyst optimization can be performed at the level of the solution-phase precursor before conversion into the active heterogeneous catalyst.

Synthesis of oxaspirannic building blocks by regioselective nitroso-Diels-Alder reactions

Spirocyclic structures: Nitroso-Diels-Alder reactions of 1,3-disubstituted cyclohexadienes were found to be regiodivergent, depending on the nitroso derivative used. Cycloaddition with Wightman's chloronitroso derivative was totally regio- and stereoselective. This methodology was applied to the synthesis of heterospiranic frameworks after N-O bond cleavage and cyclization (see scheme; Boc=tert-butoxycarbonyl, Tf=trifluoromethanesulfonyl).

Dipyrazolo[1,5-a:4',3'-c]pyridines - a new heterocyclic system accessed via multicomponent reaction

The synthesis of dipyrazolo[1,5-a:4',3'-c]pyridines is described. Easily obtainable 5-alkynylpyrazole-4-carbaldehydes, p-toluenesulfonyl hydrazide, and an aldehyde or ketone containing an α-hydrogen atom were reacted in a silver triflate catalyzed multicomponent reaction affording new tricyclic compounds with a dipyrazolo[1,5-a:4',3'-c]pyridine core. Detailed NMR spectroscopic investigations ((1)H, (13)C and (15)N) were undertaken with all obtained compounds.

Catalytic diastereo- and enantioselective annulations between transient nitrosoalkenes and indoles

Caught in transition: an efficient catalytic system is the key to the successful development of the first highly diastereo- and enantioselective annulation reaction between indoles and transient nitrosoalkenes. This robust reaction affords structurally unique architectures with up to three new chiral centers. The products can be readily elaborated into other indoline-based chiral heterocyclic motifs, including those of pyrrolidinoindoline alkaloids.

Four-component assembly of chiral N-B heterocycles with a natural product-like framework

The dative N-B bond was used to simply assemble heterocycles with a skeleton akin to the 5-oxofuro[2,3-b]furan motif. Twenty-five new N-B heterocycles were prepared via a highly efficient one-pot four-component reaction in yields and diastereoselectivities up to 95% and >97%, respectively. Several reaction intermediates were discovered using electrospray ionization mass spectroscopy which set the basis for the mechanism elucidation using DFT calculations.

Expanding the azaspiro[3.3]heptane family: synthesis of novel highly functionalized building blocks

The preparation of versatile azaspiro[3.3]heptanes carrying multiple exit vectors is disclosed. Expedient synthetic routes enable the straightforward access to these novel modules that are expected to have significance in drug discovery and design.