Trans-selective conversions of gamma-hydroxy-alpha,beta-alkynoic esters to gamma-hydroxy-alpha,beta-alkenoic esters

Gamma-hydroxy-alpha,beta-acetylenic esters are used as precursors to prepare gamma-hydroxy-alpha,beta-alkenoic esters by means of trans-selective additions of two hydrogen atoms or one hydrogen atom and one iodine atom across the triple bonds. These methods allow for the preparation of beta-substituted and alpha,beta-disubstituted alkenoic esters in highly stereoselective manners. reaction--see text]