In summary, we have of the first ring-opening of epoxides using pendant sulfamates and sulfamides. These reactions are promoted by base and proceed under mild conditions to afford oxathiazinanes and cyclic sulfamides with excellent diastereoselectivity and regiocontrol. The reactions scale well, and the products serve as synthons for ring-opening reactions. Given the ubiquity of stereochemical arrays in targets of value, we expect that this technology will be valuable to both academic and industrial organic chemists.