Aryl Sulfonates in Inversions at Secondary Carbohydrate Hydroxyl Groups: A New and Improved Route Toward 3-Azido-3-deoxy-β-d-galactopyranosides

Ferrier/Aza-Wacker/Epoxidation/Glycosylation (FAWEG) Sequence to Access 1,2-Trans 3-Amino-3-deoxyglycosides

3-Amino-3-deoxyglycosides constitute an essential class of nitrogen-containing sugars. Among them, many important 3-amino-3-deoxyglycosides possess a 1,2-trans relationship. In view of their numerous biological applications, the synthesis of 3-amino-3-deoxyglycosyl donors giving rise to a 1,2-trans glycosidic linkage is thus an important challenge. Even though glycals are highly polyvalent donors, the synthesis and reactivity of 3-amino-3-deoxyglycals have been little studied. In this work, we describe a new sequence, involving a Ferrier rearrangement and subsequent aza-Wacker cyclization that allows the rapid synthesis of orthogonally protected 3-amino-3-deoxyglycals. Finally a 3-amino-3-deoxygalactal derivative was submitted for the first time to an epoxidation/glycosylation with high yield and great diastereoselectivity, highlighting FAWEG (Ferrier/Aza-Wacker/Epoxidation/Glycosylation) as a new approach to access 1,2-trans 3-amino-3-deoxyglycosides.

Design and synthesis of novel 3-triazolyl-1-thiogalactosides as galectin-1, -3 and -8 inhibitors

Galectins are galactoside-binding proteins that play a role in various pathophysiological conditions, making them attractive targets in drug discovery. We have designed and synthesised a focused library of aromatic 3-triazolyl-1-thiogalactosides targeting their core site for binding of galactose and a subsite on its non-reducing side. Evaluation of their binding affinities for galectin-1, -3, and -8N identified acetamide-based compound 36 as a suitable compound for further affinity enhancement by adding groups at the reducing side of the galactose. Synthesis of its dichlorothiophenyl analogue 59 and the thiodigalactoside analogue 62 yielded promising pan-galectin inhibitors.

Efficient synthesis of a galectin inhibitor clinical candidate (TD139) using a Payne rearrangement/azidation reaction cascade

Selective galectin inhibitors are valuable research tools and could also be used as drug candidates. In that context, TD139, a thiodigalactoside galectin-3 inhibitor, is currently being evaluated clinically for the treatment of idiopathic pulmonary fibrosis. Herein, we describe a new strategy for the preparation of TD139. Starting from inexpensive levoglucosan, we used a rarely employed reaction cascade: Payne rearrangement/azidation process leading to 3-azido-galactopyranose. The latter intermediate was efficiently converted into TD139 in a few simple and practical steps.

Sequence-Defined Heteromultivalent Precision Glycomacromolecules Bearing Sulfonated/Sulfated Nonglycosidic Moieties Preferentially Bind Galectin-3 and Delay Wound Healing of a Galectin-3 Positive Tumor Cell Line in an In Vitro Wound Scratch Assay

Within this work, a new class of sequence-defined heteromultivalent glycomacromolecules bearing lactose residues and nonglycosidic motifs for probing glycoconjugate recognition in carbohydrate recognition domain (CRD) of galectin-3 is presented. Galectins, a family of β-galactoside-binding proteins, are known to play crucial roles in different signaling pathways involved in tumor biology. Thus, research has focused on the design and synthesis of galectin-targeting ligands for use as diagnostic markers or potential therapeutics. Heteromultivalent precision glycomacromolecules have the potential to serve as ligands for galectins. In this work, multivalency and the introduction of nonglycosidic motifs bearing either neutral, amine, or sulfonated/sulfated groups are used to better understand binding in the galectin-3 CRD. Enzyme-linked immunosorbent assays and surface plasmon resonance studies are performed, revealing a positive impact of the sulfonated/sulfated nonglycosidic motifs on galectin-3 binding but not on galectin-1 binding. Selected compounds are then tested with galectin-3 positive MCF 7 breast cancer cells using an in vitro would scratch assay. Preliminary results demonstrate a differential biological effect on MCF 7 cells with high galectin-3 expression in comparison to an HEK 293 control with low galectin-3 expression, indicating the potential for sulfonated/sulfated heteromultivalent glycomacromolecules to serve as preferential ligands for galectin-3 targeting.

3-Substituted 1-Naphthamidomethyl-C-galactosyls Interact with Two Unique Sub-sites for High-Affinity and High-Selectivity Inhibition of Galectin-3

The galectins are a family of galactose-binding proteins playing key roles in inflammatory processes and cancer. However, they are structurally very closely related, and discovery of highly selective inhibitors is challenging. In this work, we report the design of novel inhibitors binding to a subsite unique to galectin-3, which confers both high selectivity and affinity towards galectin-3. Olefin cross metathesis between allyl β-C-galactopyranosyl and 1-vinylnaphthalenes or acylation of aminomethyl β-C-galactopyranosyl with 1-naphthoic acid derivatives gave C-galactopyranosyls carrying 1-naphthamide structural elements that interacted favorably with a galectin-3 unique subsite according to molecular modeling and X-ray structural analysis of two inhibitor-galectin-3 complexes. Affinities were down to sub-µM and selectivities over galectin-1, 2, 4 N-terminal domain, 4 C-terminal domain, 7, 8 N-terminal domain, 9 N-terminal domain, and 9 C-terminal domain were high. These results show that high affinity and selectivity for a single galectin can be achieved by targeting unique subsites, which holds promise for further development of small and selective galectin inhibitors.

Systematic Tuning of Fluoro-galectin-3 Interactions Provides Thiodigalactoside Derivatives with Single-Digit nM Affinity and High Selectivity

Symmetrical and asymmetrical fluorinated phenyltriazolyl-thiodigalactoside derivatives have been synthesized and evaluated as inhibitors of galectin-1 and galectin-3. Systematic tuning of the phenyltriazolyl-thiodigalactosides' fluoro-interactions with galectin-3 led to the discovery of inhibitors with exceptional affinities (K_d down to 1-2 nM) in symmetrically substituted thiodigalactosides as well as unsurpassed combination of high affinity (K_d 7.5 nM) and selectivity (46-fold) over galectin-1 for asymmetrical thiodigalactosides by carrying one trifluorphenyltriazole and one coumaryl moiety. Studies of the inhibitor-galectin complexes with isothermal titration calorimetry and X-ray crystallography revealed the importance of fluoro-amide interaction for affinity and for selectivity. Finally, the high affinity of the discovered inhibitors required two competitive titration assay tools to be developed: a new high affinity fluorescent probe for competitive fluorescent polarization and a competitive ligand optimal for analyzing high affinity galectin-3 inhibitors with competitive isothermal titration calorimetry.