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Phenanthroline-Catalyzed Stereoselective Formation of α‑1,2-cis 2‑Deoxy-2-Fluoro Glycosides

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journal contribution
posted on 02.02.2021, 19:03 by Paul M. DeMent, Chenlu Liu, Joseph Wakpal, Richard N. Schaugaard, H. Bernhard Schlegel, Hien M. Nguyen
Phenanthroline is a heterocyclic aromatic organic compound and commonly used in coordination chemistry acting as a bidentate ligand. The C4 and C7 positions of phenanthroline can often be substituted to change the binding capabilities of the ligand. Recently, there has been a push in the field of chemistry to create environmental-friendly chemical methodologies by utilizing catalysts and minimizing solvent. Herein, we have illustrated how, at high concentrations with minimal use of solvent, the C4 and C7 positions of phenanthroline can be tuned to develop an efficient and stereoselective catalyst for the formation of α-1,2-cis-fluorinated glycosides. By activating 2-deoxy-2-fluoro glycosyl halides with phenanthroline-based catalysts, we have been able to achieve glycosylations with high levels of α-selectivities and moderate to high yields. The catalytic system has been applied to several glycosyl halide electrophiles with a range of glycosyl nucleophilic acceptors. The proposed mechanism for this catalytic glycosylation system has been investigated by density functional theory calculations, indicating that the double SN2 displacement pathways with phenanthroline catalysts have lower barriers and ensure stereoselective formation of α-1,2-cis-2-fluoro glycosides.