Biosynthesis of Terpenes. Preparation of (<i>E</i>)-1-Hydroxy-2-methyl-but-2-enyl 4-Diphosphate, an Intermediate of the Deoxyxylulose Phosphate Pathway<sup>†</sup>

(<i>E</i>)-1-Hydroxy-2-methyl-but-2-enyl 4-diphosphate (<i>E</i>-<b>6</b>) was synthesized in six reaction steps from hydroxyacetone (<b>9</b>) and (ethoxycarbonylmethenyl)-triphenylphosphorane (<b>11</b>) with an overall yield of 38%. The compound was shown to be identical with the product of IspG protein, which serves as an intermediate in the nonmevalonate terpene biosynthetic pathway.