Diaminocyclopentane - l-Lysine Adducts: Potent and selective inhibitors of human O-GlcNAcase.

A new class of compounds, namely highly substituted diaminocyclopentane-l-lysine adducts, have been discovered as potent inhibitors of O-GlcNAcase, an enzyme crucial for protein de-O-glycosylation. These inhibitors exhibit exceptional selectivity and reversibility and are the first example of human O-GlcNAcase inhibitors that are structurally related to the transition state of the rate-limiting step with the "aglycon" still in bond-length proximity. The ease of their preparation, remarkable biological activities, stability, and non-toxicity make them promising candidates for the development of anti-tau-phosphorylation agents holding significant potential for the treatment of Alzheimer's disease.

The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040: Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources.

Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve.

Highly functionalized diaminocyclopentanes: A new route to potent and selective inhibitors of human O-GlcNAcase.

A new class of compounds inhibiting de-O-glycosylation of proteins has been identified. Highly substituted diaminocyclopentanes are impressively selective reversible non-transition state O-ß-N-acetyl-d-glucosaminidase (O-GlcNAcase) inhibitors. The ease of preparative access and remarkable biological activities provide highly viable leads for the development of anti-tau-phosphorylation agents with a view to eventually ameliorating Alzheimer's disease.

Ligand-Directed Chemistry on Glycoside Hydrolases - A Proof of Concept Study.

Selective covalent labelling of enzymes using small molecule probes has advanced the scopes of protein profiling. The covalent bond formation to a specific target is the key step of activity-based protein profiling (ABPP), a method which has become an indispensable tool for measuring enzyme activity in complex matrices. With respect to carbohydrate processing enzymes, strategies for ABPP so far involve labelling the active site of the enzyme, which results in permanent loss of activity. Here, we report in a proof of concept study the use of ligand-directed chemistry (LDC) for labelling glycoside hydrolases near - but not in - the active site. During the labelling process, the competitive inhibitor is cleaved from the probe, departs the active site and the enzyme maintains its catalytic activity. To this end, we designed a building block synthetic concept for small molecule probes containing iminosugar-based reversible inhibitors for labelling of two model ß-glucosidases. The results indicate that the LDC approach can be adaptable for covalent proximity labelling of glycoside hydrolases.

Pharmacological Chaperones for ß-Galactosidase Related to GM1 -Gangliosidosis and Morquio B: Recent Advances.

A short survey on selected ß-galactosidase inhibitors as potential pharmacological chaperones for GM1 -gangliosidosis and Morquio B associated mutants of human lysosomal ß-galactosidase is provided highlighting recent developments in this particular area of lysosomal storage disorders and orphan diseases.

Synthesis of d-Galactose-Substituted Acylsilanes and Acylgermanes. Model Compounds for Visible Light Photoinitiators with Intriguing High Solubility.

A convenient synthetic method to obtain d-galactose-substituted acylsilanes and acylgermanes is described. These acyl group 14 compounds are easily accessible in good yields. Their structural properties were analyzed by a combination of NMR, single crystal X-ray crystallography, and UV/vis spectroscopy. A d-galactose-substituted tetraacylgermane represents a new interesting visible light photoinitiator based on its absorption properties as well as its high solubility.

New α-galactosidase-inhibiting aminohydroxycyclopentanes.

A set of cyclopentanoid α-galactosidase ligands was prepared from a partially protected ω-eno-aldose via a reliable (2 + 3)-cycloaddition protocol with slightly modified conditions. The obtained N-benzylisoxazolidine ring was selectively opened and the configuration of the hydroxymethylgroup was inverted. Consecutive deprotection provided an aminocyclopentane, which was N-alkylated to furnish a set of potential α-galactosidase inhibitors. Their glycosidase inhibitory activities were screened with a panel of standard glycosidases of biological significance.

Indium-mediated allylation of disaccharides.

The indium-mediated allylation followed by ozonolysis has been applied for the elongation of different disaccharides such as cellobiose, lactose and maltose. This reaction sequence and per-O-acetylation produced the expected mixture of α/ß-pyranoid as well as α/ß-furanoid isomers. The main product in all cases adopted the ß-pyranose form and could be isolated and fully characterized with the help of NMR-spin simulations. Thorough investigation of the side products throughout optimization of the conditions for the ozonolysis resulted in the discovery of a novel 12 membered bridged disaccharide.

N-Alkylated Iminosugar Based Ligands: Synthesis and Inhibition of Human Lysosomal ß-Glucocerebrosidase.

The scope of a series of N-alkylated iminosugar based inhibitors in the d-gluco as well as d-xylo configuration towards their interaction with human lysosomal ß-glucocerebrosidase has been evaluated. A versatile synthetic toolbox has been developed for the synthesis of N-alkylated iminosugar scaffolds conjugated to a variety of terminal groups via a benzoic acid ester linker. The terminal groups such as nitrile, azide, alkyne, nonafluoro-tert-butyl and amino substituents enable follow-up chemistry as well as visualisation experiments. All compounds showed promising inhibitory properties as well as selectivities for ß-glucosidases, some exhibiting activities in the low nanomolar range for ß-glucocerebrosidase.

Mechanistic Insights into the Chaperoning of Human Lysosomal-Galactosidase Activity: Highly Functionalized Aminocyclopentanes and C-5a-Substituted Derivatives of 4-epi-Isofagomine.

Glycosidase inhibitors have shown great potential as pharmacological chaperones for lysosomal storage diseases. In light of this, a series of new cyclopentanoid ß-galactosidase inhibitors were prepared and their inhibitory and pharmacological chaperoning activities determined and compared with those of lipophilic analogs of the potent ß-d-galactosidase inhibitor 4-epi-isofagomine. Structure-activity relationships were investigated by X-ray crystallography as well as by alterations in the cyclopentane moiety such as deoxygenation and replacement by fluorine of a "strategic" hydroxyl group. New compounds have revealed highly promising activities with a range of ß-galactosidase-compromised human cell lines and may serve as leads towards new pharmacological chaperones for GM1-gangliosidosis and Morquio B disease.

The CXCR4-CXCL12-Axis Is of Prognostic Relevance in DLBCL and Its Antagonists Exert Pro-Apoptotic Effects In Vitro.

In tumor cells of more than 20 different cancer types, the CXCR4-CXCL12-axis is involved in multiple key processes including proliferation, survival, migration, invasion, and metastasis. Since data on this axis in diffuse large B cell lymphoma (DLBCL) are inconsistent and limited, we comprehensively studied the CXCR4-CXCL12-axis in our DLBCL cohort as well as the effects of CXCR4 antagonists on lymphoma cell lines in vitro. In DLBCL, we observed a 140-fold higher CXCR4 expression compared to non-neoplastic controls, which was associated with poor clinical outcome. In corresponding bone marrow biopsies, we observed a correlation of CXCL12 expression and lymphoma infiltration rate as well as a reduction of CXCR4 expression in remission of bone marrow involvement after treatment. Additionally, we investigated the effects of three CXCR4 antagonists in vitro. Therefore, we used AMD3100 (Plerixafor), AMD070 (Mavorixafor), and WKI, the niacin derivative of AMD070, which we synthesized. WK1 demonstrated stronger pro-apoptotic effects than AMD070 in vitro and induced expression of pro-apoptotic genes of the BCL2-family in CXCR4-positive lymphoma cell lines. Finally, WK1 treatment resulted in the reduced expression of JNK-, ERK1/2- and NF-κB/BCR-target genes. These data indicate that the CXCR4-CXCL12-axis impacts the pathogenesis of DLBCL and represents a potential therapeutic target in aggressive lymphomas.

Synthesis of modified 1,5-imino-d-xylitols as ligands for lysosomal ß-glucocerebrosidase.

ABSTRACT: Modified 1,5-dideoxy-1,5-imino-d-xylitol analogues with different substitution patterns involving position C-1 and/or the ring nitrogen were prepared, which were designed to serve as precursors for the preparation of iminoxylitol-based ligands and tools for the elucidation and modulation of human lysosomal ß-glucocerebrosidase. Biological evaluation of the synthesized glycomimetics with a series of glycoside hydrolases revealed that these substitution patterns elicit excellent ß-glucosidase selectivities.

New lectin ligands: Testing of Amadori rearrangement products with a series of mannoside-specific lectins.

1-(N-Phenyl)amino-1-deoxy-α-D-manno-hept-2-ulose (2) and two multivalent BSA-based structures 7 and 8, d-manno-configured C-glycosyl-type compounds derived from an Amadori rearrangement, were evaluated as ligands for mannoside-specific lectins of various sources. The determination of the concentration corresponding to 50% of inhibition (IC50) is described. Multivalency turned out to effectively influence ligand selectivity and lectin binding.

Potent GH20 N-Acetyl-ß-d-hexosaminidase Inhibitors: N-Substituted 3-acetamido-4-amino-5-hydroxymethyl-cyclopentanediols.

From 1,2;3,4-di-O-isopropylidene-d-galactopyranose, a preliminary series of highly functionalized amino(hydroxymethyl)cyclopentanes was easily available. These amine-containing basic carbasugars featuring the d-galacto configuration are potent inhibitors of the GH20 ß-d-hexosaminidases probed and may bear potential as regulators of N-acetyl-d-hexosaminidase activities in vivo.

The Amadori Rearrangement for Carbohydrate Conjugation: Scope and Limitations.

The Amadori rearrangement was investigated for the synthesis of C-glycosyl-type neoglycoconjugates. Various amines including diamines, amino-functionalized glycosides, lysine derivatives, and peptides were conjugated with two different heptoses to generate non-natural C-glycosyl-type glycoconjugates of the d-gluco and d-manno series. With these studies, the scope and limitations of the Amadori rearrangement as a conjugation method have been exemplified with respect to the carbohydrate substrate, as well as the amino components.

Carbohydrate-Processing Enzymes of the Lysosome: Diseases Caused by Misfolded Mutants and Sugar Mimetics as Correcting Pharmacological Chaperones.

Lysosomal storage diseases are hereditary disorders caused by mutations on genes encoding for one of the more than fifty lysosomal enzymes involved in the highly ordered degradation cascades of glycans, glycoconjugates, and other complex biomolecules in the lysosome. Several of these metabolic disorders are associated with the absence or the lack of activity of carbohydrate-processing enzymes in this cell compartment. In a recently introduced therapy concept, for susceptible mutants, small substrate-related molecules (so-called pharmacological chaperones), such as reversible inhibitors of these enzymes, may serve as templates for the correct folding and transport of the respective protein mutant, thus improving its concentration and, consequently, its enzymatic activity in the lysosome. Carbohydrate-processing enzymes in the lysosome, related lysosomal diseases, and the scope and limitations of reported reversible inhibitors as pharmacological chaperones are discussed with a view to possibly extending and improving research efforts in this area of orphan diseases.

The Staudinger/aza-Wittig/Grignard reaction as key step for the concise synthesis of 1-C-Alkyl-iminoalditol glycomimetics.

The scope of a one-pot tandem approach for the synthesis of C-1 alkyl iminoalditol derivatives with a Staudinger/aza-Wittig/Grignard cascade has been evaluated. The reaction conditions have been optimized for two azidodeoxy aldose substrates and a range of Grignard reagents. The nature of both, substrate as well as nucleophile, was found to control the stereoselectivity of the alkyl addition to the cyclic iminium intermediate at position C-1. This approach enabled the synthesis of a collection of C-alkyl iminoalditols, which were biologically evaluated as inhibitors against a set of standard glycoside hydrolases. All compounds were found to exhibit highly selective inhibition of ß-glucosidase activity.

Synthesis of AB4-type carbohydrate scaffolds as branching units in the glycosciences.

Carbohydrate scaffolds, functionalised according to an AB4-type, were prepared on the basis of α-D-mannopyranosides with various ethyl aglycone moieties, functionalised with 'A'. Four functional groups 'B' were installed at positions 2, 3, 4, and 6 of the sugar ring. In particular, we were interested in preparing N3(NH2)4-functionalised mannosides as multifunctional branching units for further orthogonal derivatisation or immobilisation on surfaces. A detailed synthetic study was performed which revealed that an azido function 'A' had to be installed at an advanced stage of the synthesis for successful preparation of the desired AB4-type carbohydrate scaffolds. The most successful synthetic sequence involved tetra-cyanoethylation of a 2-benzyloxyethyl mannopyranoside and subsequent reduction with in situ Boc protection to achieve (NHBoc)4 functionalisation. Finally, the benzyloxyethyl aglycon was converted into the corresponding azidoethyl moiety to gain access to the desired N3(NHBoc)4-functionalised carbohydrate scaffold. Its utilisation was exemplified by straightforward synthesis of a photosensitive glycoconjugate and a tetravalent glycocluster. Such compounds may be immobilised on functional surfaces to serve as tools in cell adhesion studies.

Are D-manno-configured Amadori products ligands of the bacterial lectin FimH?

The Amadori rearrangement was employed for the synthesis of C-glycosyl-type D-mannoside analogues, namely 1-propargylamino- and 1-phenylamino-1-deoxy-α-D-manno-heptopyranose. They were investigated as ligands of type 1-fimbriated E. coli bacteria by means of molecular docking and bacterial adhesion studies. It turns out that Amadori rearrangement products have a limited activity as inhibitors of bacterial adhesion because the ß-C-glycosidically linked aglycone considerably hampers complexation within the carbohydrate binding site of the type 1-fimbrial lectin FimH.

Concise synthesis of C-1-cyano-iminosugars via a new Staudinger/aza Wittig/Strecker multicomponent reaction strategy.

A new Staudinger/aza Wittig/Strecker multicomponent reaction sequence to C-1-cyano iminoalditols has been developed. When applied to 5-azidodeoxy-d-xylose and -d-glucose as substrates the method leads smoothly in good yield and with excellent stereoselectivity to respectively, 1,5-dideoxy-1,5-imino-d-idurono nitrile and 2,6-didesoxy-2,6-imino-d-glycero-d-ido-heptononitrile.