The first enantiospecific synthesis of 2, a phosphonate isostere of phosphothreonine suitably protected for solid-phasepeptidesynthesis, has been achieved by coupling the highly face-selective conjugate addition of the lithium salt of Schöllkopf's bislactim ether to E-prop-2-enyl-phosphonates with a selective enzymatic carboxylic ester hydrolysis. The absolute configuration of the products has been