Desymmetrization of a readily derived pseudo-C(2)-symmetric monocyclic phosphate via highly diastereoselective anti-S(N)2' allylic displacement reactions is reported. This method utilizes of a wide variety of zinc-derived organocuprates to afford E-1,2-syn-configured phosphate acid building blocks. Extension of this protocol to unsymmetric monocyclic phosphates exclusively yields 1,2-anti-configured products. Within this study, stereoelectronic factors, coupled with allylic strain, ultimately govern regio- and diastereoselective cuprate reactions, further substantiating the Corey mechanism for organocuprate additions into allylic esters. [reaction: see text]