Ring-fused gem-dibromocyclopropanes as precursors to enantiomerically pure D- and L-series 3-deoxy- and 2-amino-2,3-dideoxyaldohexose derivatives

The readily available gem-dibromocyclopropanes 5 and 6 undergo silver(I)-promoted electrocyclic ring-opening and the resulting π-allyl cations trapped with a range of nucleophiles to give mixtures of cyclohexenyl bromides such as 7–9 and 17–19, respectively. Subjection of certain of these products to ozonolytic cleavage followed by reduction protocols then affords differentially protected and enantiopure D- and L-series 3-deoxy- and 2-amino-2,3-dideoxyaldohexoses.