Stereochemical variations in aqueous cycloadditions using glyco-organic substrates as a consequence of chemical manipulations on the sugar moiety.☆

Abstract Chemical modifications of the sugar moiety in dienyl glycosidesallowed us to rationalize the stereochemistry of our aqueouscycloadditions using glyco-organic substrates. In this way, several dienyl glucosides having benzyl group in 2 or 6 position of the sugar gave a stereofacial selectivity which could beanticipated. Finally, aqueous cycloaddition of 2-methyl butadienyl α-D-glucoside with methacrolein gave a mixture ofadducts in which the major diastereoisomer endo-Rewas obtained in 78% yield resulting from a 18:82 stereofacial selectivity and a 20:1 endo-exo ratio.