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 pi -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.