Synthesis of Hexenuloses and a Library of Disaccharides Possessing 3-oxo-glycal Unit

Stereoselective synthesis of 3-oxo-2-C-branched glycosides from 2,3-unsaturated sugars via [3,3]-sigmatropic rearrangement

A number of monosaccharide-derived glycals were initially converted to the corresponding 3-O-allyl 2,3-unsaturated glycosides and then subjected to Claisen rearrangement to produce 3-oxo-2-C-branched sugar derivatives with good to excellent stereoselectivity. The methodology was extended to synthesize allyl vinyl ethers derived from disaccharides. The application of the developed protocol was showcased by synthesizing the bicyclic core unit of the iridoid frameworks.

DMSO-K2S2O8 mediated iodine-free conversion of glycal C-3 ether to 3-enopyranones: synthesis of furo[3,2-c] pyrans

A straightforward, highly efficient, and regioselective method for directly converting 3-O-benzylated and silylated glycals into their corresponding enones has been developed using a DMSO-K2S2O8 reagent system. This reaction is scalable to gram quantities under mild conditions, achieving up to 80% yields. The resulting enones are valuable intermediates for the synthesis of furo[3,2-c] pyrans, which are integral components of various biologically significant scaffolds.

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.

Versatile applications of 3-OxoGlycals: A review

3-Oxoglycals are versatile building blocks with extensive applications in glycochemistry, organic, and bio-organic sciences. They serve as powerful synthons, enabling the development of diverse organic structures. This review highlights the utility of easily obtainable 3-oxoglycals as fundamental building blocks for synthesizing various compounds, including rare sugars, N-inserted compounds, fused heterocycles, medium ring compounds, polycyclic molecules, cycloadducts, and axially chiral molecules. Some of these compounds exhibit significant biological activities, while others possess valuable photophysical properties. The simplicity of these reactions, using readily available starting materials under favorable conditions, makes 3-oxoglycals a valuable tool for creating novel molecules, benefiting the scientific community in various fields.

A Short Route to the Synthesis of Digoxose Trisaccharide Glycal Donor via Mislow-Evans Rearrangement

The Mislow-Evans rearrangement was used as a key reaction to construct digitoxose-derived glycals. The same rearrangement was iteratively performed on di- and trisaccharides to form the digoxose glycal donor component present in the cardenolides digitoxin, digoxin, and gitoxin. The scalability of the trisaccharide synthesis was shown by performing the reactions on a multigram scale. Glycosylation reactions were also performed between the synthesized digoxin glycal donor and aglycons digoxigenin and gitoxigenin to synthesize novel cardenolide derivatives.