Evaluation of nonnatural L-iminosugar C,C-glycosides, a new class of C-branched iminosugars, as glycosidase inhibitors.

Capitalizing on a previously developed Staudinger/azaWittig/Grignard (SAWG)-ring contraction sequence that furnished protected six-membered L-iminosugar C,C-glycosides bearing an allyl group and various substituents at the pseudoanomeric position, the synthesis and glycosidase inhibition of a small library of six- and seven-membered L-iminosugar C,C-glycosides is reported. Their hydrogenolysis or cyclization by RCM followed by deprotection afforded eleven L-iminosugars including spirocyclic derivatives. All compounds adopt a 1C4 conformation in solution according to NMR data. Compared to previously reported branched L-iminosugars, the L-iminosugar C,C-glycosides reported herein were less potent glycosidase inhibitors. However, some of these compounds showed micromolar inhibition of human lysosome ß-glucocerebrosidase suggesting that such iminosugars could be useful to access potent CGase inhibitors by adjusting the structure/length of the pseudoanomeric substituents.

Deciphering dynamic combinatorial libraries of glycoclusters with miniaturized weak affinity chromatography coupled with mass spectrometry (nano-FAC-MS).

We report an original methodology based on affinity chromatography coupled with mass spectrometry to decipher the complexity of dynamic combinatorial libraries (DCLs) of glycoclusters. Such libraries are intended to boost the design of potential therapeutic anti-infectious agents targeting Pseudomonas aeruginosa, which is responsible for numerous diseases, mostly found in hospitals as major a cause of nosocomial infections. Dynamic combinatorial chemistry provides a rapid access to an equilibrating mixture of glycocluster candidates through the formation of reversible covalent bonds under thermodynamic control. Identifying each molecule in the complex mixture overcomes challenges due to the dynamic process. Selection of glycoclusters candidates was first realized on a model lectin (Concanavalin A, ConA). Home-made affinity nanocolumns, containing covalently immobilized ConA and have volumes in the microliter range, were used to separate DCLs of glycoclusters with respect to their specific lectin binding properties under buffered aqueous conditions. Miniaturization facilitates the inline coupling with MS detection in such purely aqueous and buffered conditions and reduces target protein consumption. Monolithic lectin-affinity columns prepared by immobilization of ConA were first characterized using a known ligand. The amount of active binding immobilized lectin is 61 ± 5 pmol on 8.5-cm length column. We demonstrated the ability of our approach to evaluate individual dissociation constants of species directly in the complex mixture. The concept was then successfully applied to the screening of DCLs of more complex glycoclusters to identify (by mass spectrometry) and rank the ligands (by relative breakthrough curve delay) according to their affinity for the immobilized lectin in a single experiment.

An Optimized Workflow for the Discovery of New Antimicrobial Compounds Targeting Bacterial RNA Polymerase Complex Formation.

Bacterial resistance represents a major health problem worldwide and there is an urgent need to develop first-in-class compounds directed against new therapeutic targets. We previously developed a drug-discovery platform to identify new antimicrobials able to disrupt the protein-protein interaction between the ß' subunit and the σ70 initiation factor of bacterial RNA polymerase, which is essential for transcription. As a follow-up to such work, we have improved the discovery strategy to make it less time-consuming and more cost-effective. This involves three sequential assays, easily scalable to a high-throughput format, and a subsequent in-depth characterization only limited to hits that passed the three tests. This optimized workflow, applied to the screening of 5360 small molecules from three synthetic and natural compound libraries, led to the identification of six compounds interfering with the ß'-σ70 interaction, and thus was capable of inhibiting promoter-specific RNA transcription and bacterial growth. Upon supplementation with a permeability adjuvant, the two most potent transcription-inhibiting compounds displayed a strong antibacterial activity against Escherichia coli with minimum inhibitory concentration (MIC) values among the lowest (0.87-1.56 µM) thus far reported for ß'-σ PPI inhibitors. The newly identified hit compounds share structural feature similarities with those of a pharmacophore model previously developed from known inhibitors.

Correction to "Discovery of Novel α-Carboline Inhibitors of the Anaplastic Lymphoma Kinase".

[This corrects the article DOI: 10.1021/acsomega.2c00507.].

Identification of non-ATP-competitive α-carboline inhibitors of the anaplastic lymphoma kinase.

The Anaplastic Lymphoma Kinase (ALK) is a therapeutic target for personalized medicine in selected cancers. Despite excellent clinical responses to ALK inhibitors, most patients develop drug resistance and relapse. New compounds with alternative binding modes are needed to overcome resistant mutants. Here we describe a medicinal chemistry effort to the design and development of novel ALK inhibitors based on a 4,6-substituted α-carboline scaffold. Active compounds were able to inhibit the gatekeeper L1196M mutant, in several cases better than the wild-type enzyme. Compound 43 showed potent non-ATP-competitive inhibition of wild-type and mutant ALK, including G1202R, in biochemical and cellular assays, as well as in xenograft mouse models.

Synthesis of Substituted Indolizidines and Quinolizidines by Regioselective Intramolecular Modified Julia Olefination of Imides.

We report the synthesis of substituted indolizidines and quinolizidines using the modified Julia olefination previously developed on imides. The study focuses on the regioselectivity of this reaction on unsymmetrically substituted imides. The scope and regioselectivity of the reaction are presented here, and its utility as a tool for synthesizing natural products is demonstrated through the total synthesis of Pandalizine A.

Access to cyclic gem-difluoroacyl scaffolds via electrochemical and visible light photocatalytic radical tandem cyclization of heteroaryl chlorodifluoromethyl ketones.

A variety of unprecedented scaffolds containing a difluoroacyl moiety were obtained in moderate to good yields, with excellent diastereoselectivity, via electrochemical or photochemical activation of difluoroacyl heteroaryles with a series of olefinic substrates.

Modified Julia Olefination on Anhydrides: Extension and Limitations. Application to the Synthesis of Maculalactone B.

The preparation of exo-enol esters from cyclic anhydrides is reported using a modified Julia olefination. The reaction is highly stereoselective. The Smiles rearrangement can be performed in a one-pot process, giving a straightforward access to exo-enol lactones. Furthermore, the reaction was extended to semistabilized sulfones, and this methodology was applied to the synthesis of maculalactone B.

Fluorinated hydroxypiperidines as selective ß-glucosidase inhibitors.

A new series of fluoroallylamines derived from hydroxypiperidines was prepared and evaluated against various glycosidases. The short synthesis of target molecules involved the modified Julia reaction between aldehydes and functionalized fluoroaminosulfones. Biological studies revealed good and selective ß-glucosidase inhibition in the micromolar range for two compounds, while the non-fluorinated analogue of the most active compound was selective towards α-glucosidase.

Synthesis and biological evaluation of benzo[4,5]imidazo[1,2-c]pyrimidine and benzo[4,5]imidazo[1,2-a]pyrazine derivatives as anaplastic lymphoma kinase inhibitors.

Chromosomal translocations involving anaplastic lymphoma kinase (ALK) are the driving mutations for a range of cancers and ALK is thus considered an attractive therapeutic target. We synthesized a series of functionalized benzo[4,5]imidazo[1,2-c]pyrimidines and benzo[4,5]imidazo[1,2-a]pyrazines by an aza-Graebe-Ullman reaction, followed by palladium-catalyzed cross-coupling reactions. A sequential regioselective cross-coupling route is reported for the synthesis of unsymmetrically disubstituted benzo[4,5]imidazo[1,2-a]pyrazines. The inhibition of ALK was evaluated and compound 19 in particular showed good activity against both the wild type and crizotinib-resistant L1196M mutant in vitro and in ALK-transfected BaF3 cells.

Synthesis of substituted exo-glucals via a modified Julia olefination and identification as selective ß-glucosidase inhibitors.

A series of fluorine and non-fluorine-substituted C-glucosylidenes (exo-glucals) has been synthesized via a modified Julia olefination. The deprotected exo-glucals were prepared in five steps from commercially available d-gluconolactone. The evaluation of this original family of compounds against a panel of glycosidases showed a highly specific in vitro activity towards mammalian ß-glucosidase depending on the double bond substituents.

Total synthesis of bistramide†A and its 36(Z)†isomers: differential effect on cell division, differentiation, and apoptosis.

The total synthesis of bistramide A and its 36(Z),39(S) and 36(Z),39(R) isomers shows that these compounds have different effects on cell division and apoptosis. The synthesis relies on a novel enol ether-forming reaction for the spiroketal fragment, a kinetic oxa-Michael cyclization reaction for the tetrahydropyran fragment, and an asymmetric crotonylation reaction for the amino acid fragment. Preliminary biological studies show a distinct pattern of influence of each of the three compounds on cell division, differentiation, and apoptosis in HL-60 cells, thus suggesting that these effects are independent activities of the natural product.

Glucose-based spiro-isoxazolines: a new family of potent glycogen phosphorylase inhibitors.

A series of glucopyranosylidene-spiro-isoxazolines was prepared through regio- and stereoselective [3+2]-cycloaddition between the methylene acetylated exo-glucal and aromatic nitrile oxides. The deprotected cycloadducts were evaluated as inhibitors of muscle glycogen phosphorylase b. The carbohydrate-based family of five inhibitors displays K(i) values ranging from 0.63 to 92.5 microM. The X-ray structures of the enzyme-ligand complexes show that the inhibitors bind preferentially at the catalytic site of the enzyme retaining the less active T-state conformation. Docking calculations with GLIDE in extra-precision (XP) mode yielded excellent agreement with experiment, as judged by comparison of the predicted binding modes of the five ligands with the crystallographic conformations and the good correlation between the docking scores and the experimental free binding energies. Use of docking constraints on the well-defined positions of the glucopyranose moiety in the catalytic site and redocking of GLIDE-XP poses using electrostatic potential fit-determined ligand partial charges in quantum polarized ligand docking (QPLD) produced the best results in this regard.

Identification of potential cellular targets of aloisine A by affinity chromatography.

Affinity chromatography was used to identify potential cellular targets of aloisine A (7-n-butyl-6-(4'-hydroxyphenyl)-5H-pyrrolo[2,3b]pyrazine), a potent inhibitor of cyclin-dependent kinases. This technique is based on the immobilization of the drug on a solid matrix, followed by identification of specifically bound proteins. To this end, both aloisine A and the protein-kinase inactive control N-methyl aloisine, bearing extended linker chains have been synthesized. We present the preparation of such analogues having the triethylene glycol chain at different positions of the molecule, as well as their immobilization on an agarose-based matrix. Affinity chromatography of various biological extracts on the aloisine matrices allowed the identification of both protein kinases and non-kinase proteins as potential cellular targets of aloisine.

The glucosinolate-myrosinase system. New insights into enzyme-substrate interactions by use of simplified inhibitors.

Myrosinase, a thioglucoside glucohydrolase, is the only enzyme able to hydrolyse glucosinolates, a unique family of molecules bearing an anomeric O-sulfated thiohydroximate function. Non-hydrolysable myrosinase inhibitors have been devised and studied for their biological interaction. Diverse modifications of the O-sulfate moiety did not result in a significant inhibitory effect, whereas replacing the D-glucopyrano residue by its carba-analogue allowed inhibition to take place. X-Ray experiments carried out after soaking allowed for the first time inclusion of a non-hydrolysable inhibitor inside the enzymatic pocket. Structural tuning of the aglycon part in its pocket is being used as a guide for the development of simplified and more potent inhibitors.

General synthesis and biological evaluation of alpha-1-C-substituted derivatives of fagomine (2-deoxynojirimycin-alpha-C-glycosides).

A general synthesis of alpha-1-C-substituted derivatives of fagomine (2-deoxynojirimycin-alpha-C-glycosides) by ring-opening reactions of an aziridine with various heteroatomic nucleophiles, including thiol, amine, alcohol, carboxylate and phosphate, is described. The nine-step reaction sequence proceeded in an overall yield of 14-28% from tri-O-benzyl-D-glucal. Biological evaluation of alpha-1-C-substituted derivatives of fagomine, of the 2-deoxy analog of alpha-homonojirimycin 19 and its 1,N-anhydro derivative 22 as glycosidase inhibitors is reported. The glycosyl phosphate mimetic 15k was found to display no inhibitory activity towards glycogen phosphorylase b and phosphoglucomutase.