Toward Bis C,C‐Glycosyl Compounds and Anomeric γ‐Glycoamino Acids through Michael Addition Reaction of Nitromethane on Z/E Push‐Pull Sugar Olefins

Abstract

AbstractThe nucleophilic addition of a nitronate anion on push‐pull anomeric sugar olefins has been studied and the results reveal that this reaction opens a new and efficient access to anomeric γ‐nitro esters when applied to furanoglycosylidenes. The 1,4‐addition reaction occurs mainly from the less‐crowded face, i.e. the opposite side to the 4,5‐isopropylidene protecting group. Very different reactivities for E and Z isomers were observed and this experimental finding was rationalized on the basis of quantum mechanical calculations. Chemical manipulation of the nitro function of these bis C,C‐glycosyl compounds led to a series of new γ‐glycoamino acids, which are chiral building blocks that may be useful for the synthesis of glycopeptides oligomers or scaffolds for the construction of bioactive compounds. Under the same reaction conditions, pyranoglycosylidenes were more prone to migration of the double bond than to the expected 1,4 addition reaction.