Delineating the physical organic profile of the 6-fluoro glycosyl donor

Deoxyfluorination tunes the aggregation of cellulose and chitin oligosaccharides and highlights the role of specific hydroxyl groups in the crystallization process

Using synthetic oligosaccharides, we examined how deoxyfluorination (site and pattern) impact the solubility and aggregation of cellulose and chitin oligomers.

6-Deoxy-6-fluoro galactofuranosides: regioselective glycosylation, unexpected reactivity, and anti-leishmanial activity

Selective glycosylation of the C-6 fluorinated galactofuranosyl acceptor 2 was studied with four galactofuranosyl donors. It was highlighted that this electron-withdrawing atom strongly impacted the behavior of the acceptor, thus leading to unprecedented glycosylation pathways. Competition between expected glycosylation of 2, ring expansion of this acceptor and furanosylation, and intermolecular aglycon transfer was observed. Further investigation of the fluorinated synthetic compounds showed that the presence of fluorine atom contributed to increase the inhibition of the growth of Leishmania tarentolae, a non-pathogenic strain of Leishmania.

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

Phosphinooxazoline (PHOX) ligands are an important class of ligands in asymmetric catalysis. We synthesized ten novel D-fructose-derived spiro-fused PHOX ligands with different steric and electronic demand. The application of two of them was tested in asymmetric allylic alkylation. The ligands are prepared in two steps from readily available 1,2-O-isopropylidene protected β-D-fructopyranoses by the BF₃·OEt₂-promoted Ritter reaction with 2-bromobenzonitrile to construct the oxazoline moiety followed by Ullmann coupling of the resulting aryl bromides with diphenylphosphine. Both steps proceeded mostly in good to high yields (57–86% for the Ritter reaction and 35–89% for the Ullmann coupling). The Ritter reaction gave two anomers, which could be separated by column chromatography. The prepared ligands showed promising results (er of up to 84:16) in Tsuji–Trost reactions with diphenylallyl acetate as model substrate.

Fluorine-directed 1,2-trans glycosylation of rare sugars

To reconcile the urgent need to access well defined β-configured 2,6-di-deoxypyranose analogues for chemical biology, with the intrinsic α-selectivity of the native system, the directing role of fluorine at C2 has been explored. Localised partial charge inversion (C-H(δ+)→ C-F(δ-)) elicits a reversal of the substrate-based α-stereoselectivity, irrespective of the protecting group electronics.