ENANTIOSPECIFIC SYNTHESIS OF 2-AMINO-3-METHYL-4-PHOSPHONOBUTANOIC ACIDS VIA 1,4-ADDITION OF LITHIATED SCHOLLKOPF ANION TO PROP-2-ENYLPHOSPHONATES

High diastereoselectivity in the conjugate addition of lithiated Schol lkopf's bislactim ethers to E- and Z-prop-2-enylphosphonates was utili zed to achieve a direct asymmetric synthesis of all four diastereoisom ers of 2-amino-3-methyl-4-phosphonobutanoic acid, i.e. (+)-(2S, 3R)-4a , (+)-(2S, 3S)-4b and their corresponding enantiomers. Their relative configuration was definitively assigned from an NMR study of oxaphosph inane derivatives of both diastereoisomers.