Enantioselective synthesis of [alpha]-fluoro-[[beta].sup.3]-amino esters: synthesis of enantiopure, orthogonally protected [alpha]-fluoro-[[beta].sup.3]-lysine

The scope of a tandem conjugate addition-fluorination sequence performed on [alpha],[beta]-unsaturated esters by using the enantiopure lithium amide derived from (S)-N-benzyl-N-([alpha]-methylbenzyl)amine, and the electrophilic fluorinating agent N-fluorobenzenesulfonimide is examined. The method is used for preparing enantiopure [alpha]-fluoro-[[beta].sup.3]-amino acids and its utility is shown by the preparation of orthogonally protected (2S,3S)-[alpha]-fluoro-[[beta].sup.3]-lysine.