Allylic polyenyl diphosphates such as geranyl and (E,E,E)-geranylgeranyl diphosphates are ubiquitous substrates for monoterpene and diterpene synthases and transferases in isoprenoid biosynthesis. These enzyme substrates were prepared in asymmetrically labeled form by reduction of 1-deuterio aldehyde precursors with (R)- and (S)-Alpine boranes®, conversion into diethyl phosphates, and SN2 displacements