Reaction of 2-alkyl-4-enamides 2, 9-15 with NIS and aqueous sodium bicarbonate results in the diastereoselective formation of the corresponding iodohydrins 3, 16-22 with essentially no iodolactone by-product. This methodology has been successfully employed for the synthesis of the epoxide intermediate 4 of the orally active Merck HIV-I protease inhibitor L-735,524.