Cyanomethyl (CNMe) ether: an orthogonal protecting group for saccharides

NFSI mediated C3-ether oxidation of glycals for the synthesis of hex-3-enuloses

Hex-3-enuloses constitute a vital carbohydrate synthetic intermediate that provide access to wide range of chiral molecules through diverse derivatizations. Herein we report synthesis of these fascinating scaffolds by oxidation of C3-ether protections on glycals in presence of N-fluorobenzenesulfonimide (NFSI) under Cu(I) catalysed conditions. Benzyl, methyl and silyl ethers have been efficiently oxidized to the carbonyl group. The oxidation has been found to be highly regioselective where an array of protecting groups were tolerant to the reaction conditions. Pyranosyl glycals from various commercially available sugars have been studied in this work to evaluate the broad substrate scope.

Amino-Acid-Derived Amides as Stereodirecting Leaving Groups for Ferrier Rearrangement via Pd(0)-Catalyzed Tsuji-Trost Reactions

Ferrier rearrangement on glycals is an efficient tool to form 2,3-dideoxy glycosides that provide access to various sugar derivatives through olefin functionalization. The classical acid-mediated transformation delivers the α-O-glycosides selectively. In this protocol, amides obtained from amino acids, glycine and proline, have been utilized as sustainable β-directing leaving groups on glycal substrates. The directing groups facilitate β-selective Ferrier rearrangements for hard alcohol nucleophiles by following the Pd(0)-catalyzed Tsuji-Trost inner sphere pathway.