l-Deoxy-D-xylulose-5.phospate (3) is an intermediate of the methylerythrit01 phosphate (MEP) pathway of isopentenyl diphosphate (IPP) biosynthesis. Recently, the formation of IPP from 3 has received much attention as it has been shown to be an important route in terpenoid biosynthesis in bacteria and plants) In plants, this mevalonate-independent! MEP pathway is generally responsible for the build-up of plastid-derived terpenoids such as isoprene, monoterpenes, diterpenes, and carotenoids.~ However, it could be shown that in some cases, the formation of the generally mevalonic acid derived sesquiterpenes and sterols also proceeds via the MEP pathway. 2 The involvement of l-deoxy-D-xylulose (phosphate) has been demonstrated by its specific incorporation in terpenoids of bacteria and plants)lntramolecular rearrangement of 3 to 2-C-methyI-Derythritol-4-phosphate 4 and several subsequent, unknown steps, finally lead to IPP. In order to study this rearrangement reaction the substrate 3 was synthetically prepared with deuterium label in position 5. This paper describes an effective synthetic alternative to the previously reported synthetic and enzymatic syntheses of 3. s