Free 2-C-methyl-d-erythritol is utilised for isoprenoid biosynthesis by Escherichia coli mutants lacking the two first enzymes of the methylerythritol phosphate pathway, the deoxyxylulose phosphate synthase and isomero-reductase. For feeding experiments, this tetrol was synthesised with an overall 43% yield from readily available 1,2-O-isopropylidene-α-d-xylofuranose, including the possibility of tritium labelling.