Asymmetric Synthesis of 4‘-Ethoxy-2‘,3‘-didehydro-2‘,3‘-dideoxynucleosides by Palladium-Catalyzed Kinetic Discrimination between the Corresponding Diastereoisomeric Lactol Acetates

4‘-Substituted nucleoside analogues have been synthesized using palladium-catalyzed asymmetric allylic amination conditions. A kinetic discrimination between the diastereomeric lactol acetates (3) produced the desired aminated products (6a−d) and recovered acetate (α-3) in high yields and <97:3 diastereoselectivity. Epimerization of the recovered lactol acetate (α-3) produced a 60:40 α/β mixture of (3), which could be resubjected, in principle, to the palladium-catalyzed asymmetric allylic amination conditions.