Glycomimetics for the inhibition and modulation of lectins

Infection and the Glycome─New Insights into Host Response

Glycans play critical roles in the host-pathogen interactions leading to infection. However, we still understand very little about the dynamic nature of glycosylation in response to infection and its function in modulating host immunity. Many of the host proteins involved in immune defense are glycoproteins. Furthermore, the innate immune system recognizes glycans. The glycoform of a protein can impact proteolytic stability, receptor interactions, serum half-life, and other aspects. New, cutting-edge chemical biology tools are shedding light on the interplay between infection and the host glycome. In this review, we highlight new work on the importance of dynamic glycosylation of host proteins in the innate and adaptive immune pathways in response to infection. These include recent findings on altered glycoprofiles of mucins, complement components, and antibodies.

Synthetic approaches of carbohydrate based self-assembling systems

Carbohydrate-based self-assembling systems are essential for the formation of advanced biocompatible materials via a bottom-up approach. The self-assembling of sugar-based small molecules has applications encompassing many research fields and has been studied extensively. In this focused review, we will discuss the synthetic approaches for carbohydrate-based self-assembling (SA) systems, the mechanisms of the assembly, as well as the main properties and applications. This review will mainly cover recent publications in the last four years from January 2020 to December 2023. We will essentially focus on small molecule self-assembly, excluding polymer-based systems, which include various derivatives of monosaccharides, disaccharides, and oligosaccharides. Glycolipids, glycopeptides, and some glycoconjugate-based systems are discussed. Typically, in each category of systems, the system that can function as low molecular weight gelators (LMWGs) will be discussed first, followed by self-assembling systems that produce micelles and aggregates. The last section of the review discusses stimulus-responsive self-assembling systems, especially those forming gels, including dynamic covalent assemblies, chemical-triggered systems, and photoresponsive systems. The review will be organized based on the sugar structures, and in each category, the synthesis of representative molecular systems will be discussed next, followed by the properties of the resulting molecular assemblies.

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

Biofilm formation is one of main causes of bacterial antimicrobial resistance infections. It is known that the soluble lectins LecA and LecB, produced by Pseudomonas aeruginosa, play a key role in biofilm formation and lung infection. Bacterial lectins are therefore attractive targets for the development of new antibiotic-sparing anti-infective drugs. Building synthetic glycoconjugates for the inhibition and modulation of bacterial lectins have shown promising results. Light-sensitive lectin ligands could allow the modulation of lectins activity with precise spatiotemporal control. Despite the potential of photoswitchable tools, few photochromic lectin ligands have been developed. We have designed and synthesized several O- and S-galactosyl azobenzenes as photoswitchable ligands of LecA and evaluated their binding affinity with isothermal titration calorimetry. We show that the synthesized monovalent glycoligands possess excellent photophysical properties and strong affinity for targeted LecA with K d values in the micromolar range. Analysis of the thermodynamic contribution indicates that the Z-azobenzene isomers have a systematically stronger favorable enthalpy contribution than the corresponding E-isomers, but due to stronger unfavorable entropy, they are in general of lower affinity. The validation of this proof-of-concept and the dissection of thermodynamics of binding will help for the further development of lectin ligands that can be controlled by light.

Analogues of the pan-selectin antagonist rivipansel (GMI-1070)

The selectin family consisting of E-, P- and L-selectin plays dominant roles in atherosclerosis, ischemia-reperfusion injury, inflammatory diseases, and metastatic spreading of some cancers. An early goal in selectin-targeted drug discovery campaigns was to identify ligands binding to all three selectins, so-called pan-selectin antagonists. The physiological epitope, tetrasaccharide sialyl Lewisx (sLex, 1) binds to all selectins, albeit with very different affinities. Whereas P- and L-selectin require additional interactions contributed by sulfate groups for high binding affinity, E-selectin can functionally bind sLex-modified glycolipids and glycoproteins. Rivipansel (3) marked the first pan-selectin antagonist, which simultaneously interacted with both the sLex and the sulfate binding site. The aim of this contribution was to improve the pan-selectin affinity of rivipansel (3) by leveraging a new class of sLex mimetics in combination with an optimized linker length to the sulfate bearing group. As a result, the pan-selectin antagonist 11b exhibits an approximatively 5-fold improved affinity for E-, as well as P-selectin.

A Fluorinated Sialic Acid Vaccine Lead Against Meningitis B and C

Inspired by the specificity of α-(2,9)-sialyl epitopes in bacterial capsular polysaccharides (CPS), a doubly fluorinated disaccharide has been validated as a vaccine lead against Neisseria meningitidis serogroups C and/or B. Emulating the importance of fluorine in drug discovery, this molecular editing approach serves a multitude of purposes, which range from controlling α-selective chemical sialylation to mitigating competing elimination. Conjugation of the disialoside with two carrier proteins (CRM197 and PorA) enabled a semisynthetic vaccine to be generated; this was then investigated in six groups of six mice. The individual levels of antibodies formed were compared and classified as highly glycan-specific and protective. All glycoconjugates induced a stable and long-term IgG response and binding to the native CPS epitope was achieved. The generated antibodies were protective against MenC and/or MenB; this was validated in vitro by SBA and OPKA assays. By merging the fluorinated glycan epitope of MenC with an outer cell membrane protein of MenB, a bivalent vaccine against both serogroups was created. It is envisaged that validation of this synthetic, fluorinated disialoside bioisostere as a potent antigen will open new therapeutic avenues.

Synthesis and unexpected binding of monofluorinated N,N'-diacetylchitobiose and LacdiNAc to wheat germ agglutinin

Fluorination of carbohydrate ligands of lectins is a useful approach to examine their binding profile, improve their metabolic stability and lipophilicity, and convert them into 19F NMR-active probes. However, monofluorination of monovalent carbohydrate ligands often leads to a decreased or completely lost affinity. By chemical glycosylation, we synthesized the full series of methyl β-glycosides of N,N'-diacetylchitobiose (GlcNAcβ(1-4)GlcNAcβ1-OMe) and LacdiNAc (GalNAcβ(1-4)GlcNAcβ1-OMe) systematically monofluorinated at all hydroxyl positions. A competitive enzyme-linked lectin assay revealed that the fluorination at the 6'-position of chitobioside resulted in an unprecedented increase in affinity to wheat germ agglutinin (WGA) by one order of magnitude. For the first time, we have characterized the binding profile of a previously underexplored WGA ligand LacdiNAc. Surprisingly, 4'-fluoro-LacdiNAc bound WGA even stronger than unmodified LacdiNAc. These observations were interpreted using molecular dynamic calculations along with STD and transferred NOESY NMR techniques, which gave evidence for the strengthening of CH/π interactions after deoxyfluorination of the side chain of the non-reducing GlcNAc. These results highlight the potential of fluorinated glycomimetics as high-affinity ligands of lectins and 19F NMR-active probes.

N-Acetylgalactosamine-4-sulfatase (Arylsulfatase B) Regulates PD-L1 Expression in Melanoma by an HDAC3-Mediated Epigenetic Mechanism

The effects of the enzyme N-acetylgalactosamine-4-sulfatase (Arylsulfatase B, ARSB), which removes the 4-sulfate group at the non-reducing end of chondroitin 4-sulfate, on the expression of PD-L1 were determined, and the underlying mechanism of PD-L1 expression was elucidated. Initial experiments in human melanoma cells (A375) showed that PD-L1 expression increased from 357 ± 31 to 796 ± 50 pg/mg protein (p < 10-11) when ARSB was silenced in A375 cells. In subcutaneous B16F10 murine melanomas, PD-L1 declined from 1227 ± 189 to 583 ± 110 pg/mg protein (p = 1.67 × 10-7), a decline of 52%, following treatment with exogenous, bioactive recombinant ARSB. This decline occurred in association with reduced tumor growth and prolongation of survival, as previously reported. The mechanism of regulation of PD-L1 expression by ARSB is attributed to ARSB-mediated alteration in chondroitin 4-sulfation, leading to changes in free galectin-3, c-Jun nuclear localization, HDAC3 expression, and effects of acetyl-H3 on the PD-L1 promoter. These findings indicate that changes in ARSB contribute to the expression of PD-L1 in melanoma and can thereby affect the immune checkpoint response. Exogenous ARSB acted on melanoma cells and normal melanocytes through the IGF2 receptor. The decline in PD-L1 expression by exogenous ARSB may contribute to the impact of ARSB on melanoma progression.

Secondary Sites of the C-type Lectin-Like Fold

C-type lectins are a large superfamily of proteins involved in a multitude of biological processes. In particular, their involvement in immunity and homeostasis has rendered them attractive targets for diverse therapeutic interventions. They share a characteristic C-type lectin-like domain whose adaptability enables them to bind a broad spectrum of ligands beyond the originally defined canonical Ca2+-dependent carbohydrate binding. Together with variable domain architecture and high-level conformational plasticity, this enables C-type lectins to meet diverse functional demands. Secondary sites provide another layer of regulation and are often intricately linked to functional diversity. Located remote from the canonical primary binding site, secondary sites can accommodate ligands with other physicochemical properties and alter protein dynamics, thus enhancing selectivity and enabling fine-tuning of the biological response. In this review, we outline the structural determinants allowing C-type lectins to perform a large variety of tasks and to accommodate the ligands associated with it. Using the six well-characterized Ca2+-dependent and Ca2+-independent C-type lectin receptors DC-SIGN, langerin, MGL, dectin-1, CLEC-2 and NKG2D as examples, we focus on the characteristics of non-canonical interactions and secondary sites and their potential use in drug discovery endeavors.

Mitigating candidiasis with acarbose by targeting Candida albicans α-glucosidase: in-silico, in-vitro and transcriptomic approaches

Biofilm-associated candidiasis poses a significant challenge in clinical settings due to the limited effectiveness of existing antifungal treatments. The challenges include increased pathogen virulence, multi-drug resistance, and inadequate penetration of antimicrobials into biofilm structures. One potential solution to this problem involves the development of novel drugs that can modulate fungal virulence and biofilm formation, which is essential for pathogenesis. Resistance in Candida albicans is initiated by morphological changes from yeast to hyphal form. This transition triggers a series of events such as cell wall elongation, increased adhesion, invasion of host tissues, pathogenicity, biofilm formation, and the initiation of an immune response. The cell wall is a critical interface for interactions with host cells, primarily through various cell wall proteins, particularly mannoproteins. Thus, cell wall proteins and enzymes are considered potential antifungal targets. In this regard, we explored α-glucosidase as our potential target which plays a crucial role in processing mannoproteins. Previous studies have shown that inhibition of α-glucosidase leads to defects in cell wall integrity, reduced adhesion, diminished secretion of hydrolytic enzymes, alterations in immune recognition, and reduced pathogenicity. Since α-glucosidase, primarily converts carbohydrates, our study focuses on FDA-approved carbohydrate mimic drugs (Glycomimetics) with well-documented applications in various biological contexts. Through virtual screening of 114 FDA-approved carbohydrate-based drugs, a pseudo-sugar Acarbose, emerged as a top hit. Acarbose is known for its pharmacological potential in managing type 2 diabetes mellitus by targeting α-glucosidase. Our preliminary investigations indicate that Acarbose effectively inhibits C. albicans biofilm formation, reduces virulence, impairs morphological switching, and hinders the adhesion and invasion of host cells, all at very low concentrations in the nanomolar range. Furthermore, transcriptomic analysis reveals the mechanism of action of Acarbose, highlighting its role in targeting α-glucosidase.

Stereoselective Synthesis of the Gal-α-(1→3)-Gal-β-(1→3)-GlcNAc Trisaccharide: a new Ligand for DCAR and Mincle C-Type Lectin Receptors

In this work, we have discovered that the Gal-α-(1→3)-Gal-β-(1→3)-GlcNAc trisaccharide, a fragment of the B antigen Type-1, is a new ligand of two C-type lectin receptors (CLRs) i. e. DCAR and Mincle which are key players in different types of autoimmune diseases. Accordingly, we report here on a straightforward methodology to access pure Gal-α-(1→3)-Gal-β-(1→3)-GlcNAc trisaccharide. A spacer with a terminal primary amine group was included at the reducing end of the GlcNAc residue thus ensuring the further functionalization of the trisaccharide Gal-α-(1→3)-Gal-β-(1→3)-GlcNAc.

Antimicrobial activity and structure-activity relationships of molecules containing mono- or di- or oligosaccharides: An update

Bacterial infections are the second leading cause of death worldwide, and the evolution and widespread distribution of antibiotic-resistance elements in bacterial pathogens exacerbate the threat crisis. Carbohydrates participate in bacterial infection, drug resistance and the process of host immune regulation. Numerous antimicrobials derived from carbohydrates or contained carbohydrate scaffolds that are conducive to an increase in pathogenic bacteria targeting, the physicochemical properties and druggability profiles. In the paper, according to the type and number of sugar residues contained in antimicrobial molecules collected from the literatures ranging from 2014 to 2024, the antimicrobial activities, action mechanisms and structure-activity relationships were delineated and summarized, for purpose to provide the guiding template to select the type and size of sugars in the design of oligosaccharide-based antimicrobials to fight the looming antibiotic resistance crisis.

CYpHER: Catalytic extracellular targeted protein degradation with high potency and durable effect

Many disease-causing proteins have multiple pathogenic mechanisms, and conventional inhibitors struggle to reliably disrupt more than one. Targeted protein degradation (TPD) can eliminate the protein, and thus all its functions, by directing a cell's protein turnover machinery towards it. Two established strategies either engage catalytic E3 ligases or drive uptake towards the endolysosomal pathway. Here we describe CYpHER (CatalYtic pH-dependent Endolysosomal delivery with Recycling) technology with potency and durability from a novel catalytic mechanism that shares the specificity and straightforward modular design of endolysosomal uptake. By bestowing pH-dependent release on the target engager and using the rapid-cycling transferrin receptor as the uptake receptor, CYpHER induces endolysosomal target delivery while re-using drug, potentially yielding increased potency and reduced off-target tissue exposure risks. The TfR-based approach allows targeting to tumors that overexpress this receptor and offers the potential for transport to the CNS. CYpHER function was demonstrated in vitro with EGFR and PD-L1, and in vivo with EGFR in a model of EGFR-driven non-small cell lung cancer.

Insights on Pseudomonas aeruginosa Carbohydrate Binding from Profiles of Cystic Fibrosis Isolates Using Multivalent Fluorescent Glycopolymers Bearing Pendant Monosaccharides

Pseudomonas aeruginosa contributes to frequent, persistent, and, often, polymicrobial respiratory tract infections for individuals with cystic fibrosis (CF). Chronic CF infections lead to bronchiectasis and a shortened lifespan. P. aeruginosa expresses numerous adhesins, including lectins known to bind the epithelial cell and mucin glycoconjugates. Blocking carbohydrate-mediated host-pathogen and intra-biofilm interactions critical to the initiation and perpetuation of colonization offer promise as anti-infective treatment strategies. To inform anti-adhesion therapies, we profiled the monosaccharide binding of P. aeruginosa from CF and non-CF sources, and assessed whether specific bacterial phenotypic characteristics affected carbohydrate-binding patterns. Focusing at the cellular level, microscopic and spectrofluorometric tools permitted the solution-phase analysis of P. aeruginosa binding to a panel of fluorescent glycopolymers possessing distinct pendant monosaccharides. All P. aeruginosa demonstrated significant binding to glycopolymers specific for α-D-galactose, β-D-N-acetylgalactosamine, and β-D-galactose-3-sulfate. In each culture, a small subpopulation accounted for the binding. The carbohydrate anomeric configuration and sulfate ester presence markedly influenced binding. While this opportunistic pathogen from CF hosts presented with various colony morphologies and physiological activities, no phenotypic, physiological, or structural feature predicted enhanced or diminished monosaccharide binding. Important to anti-adhesive therapeutic strategies, these findings suggest that, regardless of phenotype or clinical source, P. aeruginosa maintain a small subpopulation that may readily associate with specific configurations of specific monosaccharides. This report provides insights into whole-cell P. aeruginosa carbohydrate-binding profiles and into the context within which successful anti-adhesive and/or anti-virulence anti-infective agents for CF must contend.

Galectins in epithelial-mesenchymal transition: roles and mechanisms contributing to tissue repair, fibrosis and cancer metastasis

Galectins are soluble glycan-binding proteins that interact with a wide range of glycoproteins and glycolipids and modulate a broad spectrum of physiological and pathological processes. The expression and subcellular localization of different galectins vary among tissues and cell types and change during processes of tissue repair, fibrosis and cancer where epithelial cells loss differentiation while acquiring migratory mesenchymal phenotypes. The epithelial-mesenchymal transition (EMT) that occurs in the context of these processes can include modifications of glycosylation patterns of glycolipids and glycoproteins affecting their interactions with galectins. Moreover, overexpression of certain galectins has been involved in the development and different outcomes of EMT. This review focuses on the roles and mechanisms of Galectin-1 (Gal-1), Gal-3, Gal-4, Gal-7 and Gal-8, which have been involved in physiologic and pathogenic EMT contexts.

Deconstructing Best-in-Class Neoglycoclusters as a Tool for Dissecting Key Multivalent Processes in Glycosidase Inhibition

Multivalency represents an appealing option to modulate selectivity in enzyme inhibition and transform moderate glycosidase inhibitors into highly potent ones. The rational design of multivalent inhibitors is however challenging because global affinity enhancement relies on several interconnected local mechanistic events, whose relative impact is unknown. So far, the largest multivalent effects ever reported for a non-polymeric glycosidase inhibitor have been obtained with cyclopeptoid-based inhibitors of Jack bean α-mannosidase (JBα-man). Here, we report a structure-activity relationship (SAR) study based on the top-down deconstruction of best-in-class multivalent inhibitors. This approach provides a valuable tool to understand the complex interdependent mechanisms underpinning the inhibitory multivalent effect. Combining SAR experiments, binding stoichiometry assessments, thermodynamic modelling and atomistic simulations allowed us to establish the significant contribution of statistical rebinding mechanisms and the importance of several key parameters, including inhitope accessibility, topological restrictions, and electrostatic interactions. Our findings indicate that strong chelate-binding, resulting from the formation of a cross-linked complex between a multivalent inhibitor and two dimeric JBα-man molecules, is not a sufficient condition to reach high levels of affinity enhancements. The deconstruction approach thus offers unique opportunities to better understand multivalent binding and provides important guidelines for the design of potent and selective multiheaded inhibitors.

Design, synthesis, biological evaluation and docking study of some new aryl and heteroaryl thiomannosides as FimH antagonists

FimH is a mannose-recognizing lectin that is expressed by Escherichia coli guiding its ability to adhere and infect cells. It is involved in pathogenesis of urinary tract infections and Chron's disease. Several X-ray structure-guided ligand design studies were extensively utilized in the discovery and optimization of small molecule aryl mannoside FimH antagonists. These antagonists retain key specific interactions of the mannose scaffolds with the FimH carbohydrate recognition domains. Thiomannosides are attractive and stable scaffolds, and this work reports the synthesis of some of their new aryl and heteroaryl derivatives as FimH antagonists. FimH-competitive binding assays as well as biofilm inhibition of the new compounds (24-32) were determined in comparison with the reference n-heptyl α-d-mannopyranoside (HM). The affinity among these compounds was found to be governed by the structure of the aryl and heteroarylf aglycones. Two compounds 31 and 32 revealed higher activity than HM. Molecular docking and total hydrophobic to topological polar surface area ratio calculations attributed to explain the obtained biological results. Finally, the SAR study suggested that introducing an aryl or heteroaryl aglycone of sufficient hydrophobicity and of proper orientation within the tyrosine binding site considerably enhance binding affinity. The potent and synthetically feasible FimH antagonists described herein hold potential as leads for the development of sensors for detection of E. coli and treatment of its diseases.

Glycolanguage of the oral microbiota

The oral cavity harbors a diverse and dynamic bacterial biofilm community which is pivotal to oral health maintenance and, if turning dysbiotic, can contribute to various diseases. Glycans as unsurpassed carriers of biological information are participating in underlying processes that shape oral health and disease. Bacterial glycoinfrastructure-encompassing compounds as diverse as glycoproteins, lipopolysaccharides (LPSs), cell wall glycopolymers, and exopolysaccharides-is well known to influence bacterial fitness, with direct effects on bacterial physiology, immunogenicity, lifestyle, and interaction and colonization capabilities. Thus, understanding oral bacterias' glycoinfrastructure and encoded glycolanguage is key to elucidating their pathogenicity mechanisms and developing targeted strategies for therapeutic intervention. Driven by their known immunological role, most research in oral glycobiology has been directed onto LPSs, whereas, recently, glycoproteins have been gaining increased interest. This review draws a multifaceted picture of the glycolanguage, with a focus on glycoproteins, manifested in prominent oral bacteria, such as streptococci, Porphyromonas gingivalis, Tannerella forsythia, and Fusobacterium nucleatum. We first define the characteristics of the different glycoconjugate classes and then summarize the current status of knowledge of the structural diversity of glycoconjugates produced by oral bacteria, describe governing biosynthetic pathways, and list biological roles of these energetically costly compounds. Additionally, we highlight emerging research on the unraveling impact of oral glycoinfrastructure on dental caries, periodontitis, and systemic conditions. By integrating current knowledge and identifying knowledge gaps, this review underscores the importance of studying the glycolanguage oral bacteria speak to advance our understanding of oral microbiology and develop novel antimicrobials.

Does size matter? - Comparing pyranoses with septanoses as ligands of the bacterial lectin FimH

The pharmacological modulation of disease-relevant carbohydrate-protein interactions represents an underexplored area of medicinal chemistry. One particular challenge in the design of glycomimetic compounds is the inherent instability of the glycosidic bond toward enzymatic cleavage. This problem has traditionally been approached by employing S-, N-, or C-glycosides with reduced susceptibility toward glycosidases. The application of ring-extended glycomimetics is an innovative approach to circumvent this issue. On the example of the bacterial adhesin FimH, it was explored how design principles from pyranose glycomimetics transfer to analogous septanose structures. A series of ring-extended FimH antagonists exhibiting the well-proven pharmacophore necessary for targeting the tyrosine-gate of FimH was synthesized. The resulting septanoses were evaluated for their affinity to the conformationally rigid isolated lectin domain of FimH (FimHLD), as well as a structurally flexible full-length FimH (FimHFL) construct. Some elements of potent mannoside-based FimH antagonists could be successfully transferred to septanose-based ligands, ultimately resulting in a 32-fold increase in binding affinity. Interestingly, the canonical ca. 100-fold loss of binding affinity between FimHLD and FimHFL is partly mitigated by the more flexible septanose antagonists, hinting at potentially differing interaction features of the flexible glycomimetics with intermediately populated states during the conformational transition of FimHFL.

Synthesis and Biological Evaluation of New Dihydrofuro[3,2-b]piperidine Derivatives as Potent α-Glucosidase Inhibitors

Inhibition of glycoside hydrolases has widespread application in the treatment of diabetes. Based on our previous findings, a series of dihydrofuro[3,2-b]piperidine derivatives was designed and synthesized from D- and L-arabinose. Compounds 32 (IC50 = 0.07 μM) and 28 (IC50 = 0.5 μM) showed significantly stronger inhibitory potency against α-glucosidase than positive control acarbose. The study of the structure-activity relationship of these compounds provides a new clue for the development of new α-glucosidase inhibitors.

Anti-Angiogenic and Anti-Scarring Dual Effect of Galectin-3 Inhibition in Mouse Models of Corneal Wound Healing

Corneal scarring is the third leading cause of global blindness. Neovascularization of ocular tissues is a major predisposing factor in scar development. Although corneal transplantation is effective in restoring vision, some patients are at high risk for graft rejection due to the presence of blood vessels in the injured cornea. Current treatment options for controlling corneal scarring are limited, and outcomes are typically poor. In this study, topical application of a small-molecule inhibitor of galectin-3, GB1265, in mouse models of corneal wound healing, led to the reduction of the following in injured corneas: i) corneal angiogenesis; ii) corneal fibrosis; iii) infiltration of immune cells; and iv) expression of the proinflammatory cytokine IL-1β. Four independent techniques (RNA sequencing, NanoString, real-time quantitative RT-PCR, and Western blot analysis) determined that decreased corneal opacity in the galectin-3 inhibitor-treated corneas was associated with decreases in the numbers of genes and signaling pathways known to promote fibrosis. These findings allowed for a high level of confidence in the conclusion that galectin-3 inhibition by the small-molecule inhibitor GB1265 has dual anti-angiogenic and anti-scarring effects. Targeting galectin-3 by GB1265 is, thus, attractive for the development of innovative therapies for a myriad of ocular and nonocular diseases characterized by pathologic angiogenesis and fibrosis.

Stable Amide Activation of N-Acetylated Glycosamines for the Synthesis of Fused Polycyclic Glycomimetics

N-Acetylation of carbohydrates is an underexplored target for chemoselective derivatization and generation of glycomimetic scaffolds. Through mild amide activation, we report that N-acetimidoyl heterocycles are stable in neutral or basic conditions yet are excellent leaving groups through acid catalysis. While this specific reactivity could prove broadly useful in amide activation strategies, stably activated N-acetylated sugars can also be diversified using libraries of hydrazides. We optimized an acid-catalyzed one-pot sequence that includes nucleophilic displacement, cyclodehydration, and intramolecular glycosylation to ultimately deliver pyranosides fused to morpholines or piperazines. This strategy of stable activation followed by acid-triggered reaction sequences exemplifies the efficient assembly of 3D-rich fused glycomimetic libraries.

HumanLectome, an update of UniLectin for the annotation and prediction of human lectins

The UniLectin portal (https://unilectin.unige.ch/) was designed in 2019 with the goal of centralising curated and predicted data on carbohydrate-binding proteins known as lectins. UniLectin is also intended as a support for the study of lectomes (full lectin set) of organisms or tissues. The present update describes the inclusion of several new modules and details the latest (https://unilectin.unige.ch/humanLectome/), covering our knowledge of the human lectome and comprising 215 unevenly characterised lectins, particularly in terms of structural information. Each HumanLectome entry is protein-centric and compiles evidence of carbohydrate recognition domain(s), specificity, 3D-structure, tissue-based expression and related genomic data. Other recent improvements regarding interoperability and accessibility are outlined.

One-pot nucleophilic substitution-double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

The nucleophilic substitution of benzylic bromides with sodium azide was combined with a subsequent copper-catalyzed (3 + 2) cycloaddition with terminal alkynes. This one-pot process was developed with a simple model alkyne, but then applied to more complex alkynes bearing enantiopure 1,2-oxazinyl substituents. Hence, the precursor compounds 1,2-, 1,3- or 1,4-bis(bromomethyl)benzene furnished geometrically differing bis(1,2,3-triazole) derivatives. The use of tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) as ligand for the click step turned out to be very advantageous. The compounds with 1,2-oxazinyl end groups can potentially serve as precursors of divalent carbohydrate mimetics, but the reductive cleavage of the 1,2-oxazine rings to aminopyran moieties did not proceed cleanly with these compounds.