Novel transformations of 2 3 Unsaturated sugars

Abstract

18 newlineChapter 1 newlineGlycals: A powerful transformation tool newlinein glyco-chemistry newlineAbstract newlineGlycals also called as the cyclic enol ethers, are well known scaffolds in the synthetic newlinecarbohydrate chemistry. Due to the presence of electron rich double bond in glycals, various newlinechemical transformations are introduced in mono- and disaccharide derived glycals with good newlineregio- and stereo selectivity. Few straightforward synthetic applications like cyclopropanation, newlineglycosylation, halo-acetalization, synthesis of deoxy sugars, carbon branched sugar and imino newlinesugar are highlighted. Although an enormous research work has been carried out in the past 50 newlineyears on the 1,2-unsaturated sugar derivatives, 2,3-unsaturated systems has also contributed newlineimmensely in the advancement of carbohydrate chemistry. The basic idea and motivation of the newlinethesis work is specified over the advancement of the chemistry and the application of 2,3- newlineunsaturated sugar derivatives. newline41 newlineChapter 2 newlineSynthesis of Hexenuloses and a Library newlineof Disaccharides Possessing 3-oxo-glycal newlineUnit newlineAbstract newlineAn efficient method for the synthesis of monosaccharides and disaccharides possessing 3-oxoglycal newlineunit is discussed. An array of monosaccharides and disaccharide-derived glycals are newlineconverted to the corresponding hexenuloses via three key steps involving halo-alkoxylation, newlinedehydrohalogenation, and ketalyzation reactions. Several 3-oxo-glycals are synthesized to show newlinethe generality and importance of the methodology. Further, the post-synthetic transformations are newlinecarried out to synthesize a rare-sugar disaccharide donor unit present as part of trisaccharide newlinemoiety in the reported natural product, versipelostatin. newline250 newlineChapter 3 newlineSynthesis of 2C-branched sugars via newlineClaisen rearrangement newlineAbstract: newlineThis chapter encompasses the Claisen rearrangement of carbohydrate-derived allyl-vinyl ethers newlinefor effective construction of 2-C-branched sugar derivatives. A suitable 3-O-alkenylated glycal is newlinesynthesized as the key precursor. The methodology is designed with 3 key steps: 1) iodobenzoxylati