José Kovensky

Molecularly Imprinted Microgels as Enzyme Inhibitors

We demonstrate, on the example of trypsin, the use of water-soluble molecularly imprinted polymer microgels as specific enzyme inhibitors. Using a strong anchoring monomer, methacryloylaminobenzamidine, the growing polymer chains are confined to close proximity of the substrate recognition site of our model enzyme. The microgels bind selectively trypsin over other proteins of similar size and molecular weight, and show competitive inhibition of trypsin with an inhibition constant K(i) of 79 nM, making them more potent inhibitors than the low molecular-weight competitive inhibitor benzamidine by almost 3 orders of magnitude. We believe that these tailor-made materials with biological activity have potential for future drug development that extends beyond enzyme inhibition.

Synthetic Multimeric Heptyl Mannosides as Potent Antiadhesives of Uropathogenic Escherichia coli

Sweet medicine: Multimeric glycoconjugates with valencies ranging from one to four were synthesized by click chemistry. Unprecedented adhesion inhibitions of piliated E. coli to human bladder cells were recorded with the multimers; a tetravalent derivative showed inhibitory concentrations 6000‐ and 64‐fold lower than mannose and heptyl α‐D‐mannoside, respectively.

Clustering of Escherichia coli Type‐1 Fimbrial Adhesins by Using Multimeric Heptyl α‐D‐Mannoside Probes with a Carbohydrate Core

Heptyl α-D-mannoside (HM) is a strong inhibitor of the FimH lectin that mediates the initial adhesion of the uropathogenic Escherichia coli (E. coli) to the bladder cells. We designed a set of multivalent HM ligands based on carbohydrate cores with structural valencies that range from 1 to 7. The chemical strategy used to construct the regular hydrophilic structures consisted of the repetition of a critical glucoside fragment. A primary amino group was grafted at the sugar reducing end to couple the multimers to a fluorescent label. A one-pot synthetic approach was developed to tether the ligands and the fluorescein isothiocyanate (FITC) probe to the scaffold simultaneously. Isothermal calorimetry with the monomeric FimH lectin revealed nanomolar affinities and saturation of all structurally available binding sites on the multivalent HM ligands. Direct titrations domain showed almost strict correlation of enthalpy-entropy compensation with increasing valency of the ligand, whereas reverse titration calorimetry demonstrated negative cooperativity between the first and the second binding site of the divalent heptyl mannoside. A multivalency effect was nevertheless observed by inhibiting the haemagglutination of type-1 piliated UTI89 E. coli, with a titer as low as 60 nM for the heptavalent HM ligand. An FITC-labeled HM trimer showed capture and cross-linking of living bacteria in solution, a phenomenon not previously described with low-valency ligands.

Heptyl α-D-mannosides grafted on a β-cyclodextrin core to interfere with Escherichia coli adhesion: an in vivo multivalent effect.

n-Heptyl α-D-mannoside (HM) has previously been identified as a nanomolar FimH antagonist able to prevent Escherichia coli adhesion. We have designed mono- and heptavalent glycoconjugates in which HM is tethered to β-cyclodextrin (β-CD) through short and long spacers. One-pot click or co-clicking procedures were developed to directly obtain the glycoconjugates from unprotected HM and β-CD precursors. These FimH antagonists were examined biophysically and in vivo. Reverse titrations by isothermal calorimetry led to trapping of the short-tethered heptavalent β-CD in a complex with three FimH lectins. Combined dynamic light scattering and small-angle X-ray solution scattering data allowed the construction of a model of the FimH trimer. The heptavalent β-CDs were shown to capture and aggregate living bacteria in solution and are therefore also able to aggregate FimH when attached to different bacteria pili. The first in vivo evaluation of multivalent FimH inhibitors has been performed. The heptavalent β-CDs proved to be much more effective anti-adhesive agents than monovalent references with doses of around 2 μg instilled in the mouse bladder leading to a significantly decreased E. coli load. Intravenously injected radiolabeled glycoconjugates can rapidly reach the mouse bladder and >2 μg concentrations can easily be retained over 24 h to prevent fluxing bacteria from rebinding.

Amphiphilic 1-deoxynojirimycin derivatives through click strategies for chemical chaperoning in N370S Gaucher cells.

In Gaucher disease (GD), mutant β-glucocerebrosidases (β-GCase) that are misfolded are recognized by the quality control machinery of the endoplasmic reticulum (ER) and degraded proteolytically. Hydrophobic iminosugars can be used as pharmacological chaperones to provide an improvement in the folding of the enzyme and promote trafficking from the ER. We have developed here an efficient click procedure to tether hydrophobic substituents to N-azidopropyl-1-deoxynojirimycin. A set of 14 original iminosugars was designed and evaluated for inhibition of commercially available glucosidases. Most of the compounds were micromolar inhibitors of those enzymes. In vitro inhibition assays with the N370S β-GCase revealed that the sublibrary containing the derivatives with aromatic aglycons displayed the highest inhibitory potency. Chaperone activity of the whole set of synthetic compounds was also explored in mutant Gaucher cells. The most active compound gave a nearly 2-fold increase in enzyme activity at 20 μM, a significantly higher value than the 1.33-fold recorded for the reference compound N-nonyl-1-deoxynojirimycin (N-nonyl-DNJ). As previously reported with bicyclic sp(2)-iminosugars (Luan, Z.; Higaki, K.; Aguilar-Moncayo, M.; Ninomiya, H.; Ohno, K.; García-Moreno, M. I.; Ortiz Mellet, C.; García Fernández, J. M.; Suzuki, Y. ChemBioChem 2009, 10, 2780), in vitro inhibition of β-GCase measured for the compounds did not correlate with the cellular chaperone activity. The potency of new iminosugar chaperones is therefore not predictable from structure-activity relationships studies based on the in vitro β-GCase inhibition.

Multimeric Lactoside “Click Clusters” as Tools to Investigate the Effect of Linker Length in Specific Interactions with Peanut Lectin, Galectin-1, and -3

Multimeric lactosides based on carbohydrate scaffolds with valencies ranging from 1 to 4 and different linker lengths were synthesized by a copper‐catalyzed azide–alkyne cycloaddition (CuAAC). The binding affinities and crosslinking abilities of the new “click clusters” toward biologically relevant galectins (gal‐1, gal‐3) and peanut lectin were evaluated by fluorescent polarization assay (FPA) and enzyme‐linked lectin assay (ELLA), respectively. FPA indicated that the binding affinities of the synthetic multilactosides towards the galectins increased proportionally with their lactosyl content, without significant differences due to the spacer length. ELLA evidenced a modest cluster effect for the multivalent conjugates, with a relative potency per lactoside ranging from 2.1 to 3.2. Nearly identical binding affinities were recorded for derivatives differing in the length of the linkers, in agreement with the FPA data. These results demonstrate that this parameter does not significantly influence the recognition process when interactions occur at a single lectin site. Molecular dynamics revealed that glycoconjugates adopt a pseudoglobular structure with a random localization of the lactoside residues. These spatial distributions were observed irrespective of the linker length; this explains the virtually equal affinities recorded by ELLA. In contrast, two‐site “sandwich” ELLA clearly revealed that multivalent derivatives bearing the longest spacers were more efficient for crosslinking lectins. Intrinsic affinities, devoid of aggregation effects, and crosslinking capabilities are, therefore, not directly related phenomena that must be taking into consideration in neoglycoconjugate design for specific applications.

Synthesis of Multivalent Glycoclusters from 1-Thio-β-d-galactose and Their Inhibitory Activity against the β-Galactosidase from E. coli

The synthesis of multivalent glycoclusters, designed to be compatible with biological systems, is reported. A variety of 1-thio-β-D-galactosides linked to a terminal triple bond through oligoethyleneglycol chains of variable lengths has been synthesized. Also, azide-containing oligosaccharide scaffolds were prepared from trehalose, maltose, and maltotriose by direct azidation with NaN(3)/PPh(3)/CBr(4). Click reaction between the thiogalactoside residues and the azide scaffolds under microwave irradiation afforded a family of glycoclusters containing 1 to 4 residues of 1-thio-β-D-galactose. The yields went from moderate to excellent, depending on the valency of the desired product. Deacetylation with Et(3)N/MeOH/H(2)O led to the final products. Complete characterization of the products was performed by NMR spectroscopy and HR-MS techniques. Their activities as inhibitors of β-galactosidase from E. coli were determined by using the Lineweaver-Burk method. The use of hydrophilic carbohydrate scaffolds for the synthesis of multivalent galactosides represents an interesting approach to improve their pharmacokinetics and bioavailability. In addition, the presence of the thioglycosidic bond will improve their stability in biological fluids.

Synthesis of Glycosides of Glucuronic, Galacturonic and Mannuronic Acids: An Overview

Uronic acids are carbohydrates present in relevant biologically active compounds. Most of the latter are glycosides or oligosaccharides linked by their anomeric carbon, so their synthesis requires glycoside-bond formation. The activation of this anomeric center remains difficult due to the presence of the electron-withdrawing C-5 carboxylic group. Herein we present an overview of glucuronidation, mannuronidation and galacturonidation reactions, including syntheses of prodrugs, oligosaccharides and stereochemical aspects.

A click procedure with heterogeneous copper to tether technetium-99m chelating agents and rhenium complexes. Evaluation of the chelating properties and biodistribution of the new radiolabelled glucose conjugates.

An efficient protocol was developed to tether chelating agents and rhenium complexes onto a glucoside scaffold with a heterogeneous copper catalyst via click chemistry. The supported catalyst avoids the formation of unwanted copper complexes during the cyclisation step. The possibility to graft a pre-chelated M(CO)(3) core by click chemistry onto a biomolecule was highlighted for the first time. (99m)Tc(CO)(3)-glucoconjugates displayed excellent in vitro stability, a fast in vivo blood clearance and a low specific organ uptake or long-term retention in spleen and stomach.

Selective TEMPO‐Catalyzed Chemicals vs. Electrochemical Oxidation of Carbohydrate Derivatives

TEMPO‐catalyzed electrochemical oxidation of carbohydrate derivatives was performed and compared with chemical oxidation, which requires the use of co‐oxidants. Allyl‐protected derivatives could be readily oxidized by both methods. Electrochemical selective oxidation of primary positions has been adapted to unprotected mono‐ and oligosaccharides.