77Se-Enriched Selenoglycoside Enables Significant Enhancement in NMR Spectroscopic Monitoring of Glycan–Protein Interactions

Detailed investigation of ligand–protein interactions is essential for better understanding of biological processes at the molecular level. Among these binding interactions, the recognition of glycans by lectins is of particular importance in several diseases, such as cancer; therefore, inhibition of glycan-lectin/galectin interactions represents a promising perspective towards developing therapeutics controlling cancer development. The recent introduction of 77Se NMR spectroscopy for monitoring the binding of a selenoglycoside to galectins prompted interest to optimize the sensitivity by increasing the 77Se content from the natural 7.63% abundance to 99%. Here, we report a convenient synthesis of 77Se-enriched selenodigalactoside (SeDG), which is a potent ligand of the medically relevant human galectin-3 protein, and proof of the expected sensitivity gain in 2D 1H, 77Se correlation NMR experiments. Our work opens perspectives for adding isotopically enriched selenoglycans for rapid monitoring of lectin-binding of selenated as well as non-selenated ligands and for ligand screening in competition experiments.

Synthesis of 4-Organoselanyl-1H-pyrazoles: Oxone®-Mediated Electrophilic Cyclization of α,β-Alkynyl Hydrazones by Using Diorganyl Diselenides

A simple and efficient method for the synthesis of 4‑organoselanyl-1H-pyrazoles has been developed, taking place under metal- and halogen-free conditions. Electrophilic species of selenium were easily generated in situ by the reaction of diorganyl diselenides with Oxone® in ethanol as solvent in an open-flask at 70 °C. These electrophilic selenium species were employed in the selenylation/cyclization of α,β-alkynyl hydrazones, giving the title compounds in moderate to excellent yields. The final species of selenium obtained from the reaction of diphenyl diselenide with Oxone® were characterized by 77Se NMR spectroscopy and high-resolution mass spectrometry (HRMS).