Carbohydrate-derived PSE acetals: controlled base-induced ring cleavage

Retro-Michael type reactions applied to PSE acetals protecting monosaccharides led either to complete removal or to ring-cleavage. In protic medium, application of standard basic conditions resulted in acetal deprotection, while the use of butyl lithium in aprotic medium allowed controlled ring-cleavage. A regio- and stereoselective C- over O-alkylation was observed during the process. Furthermore, depending on the substrates and the reaction conditions involved, new carbohydrate-derived β-alkoxyvinyl sulfones were obtained with varying regioselectivity.