SummaryThe acid catalyzed reaction of glycerol-d5 with bromoacetaldehyde dimethyl acetal affords the corresponding 2-bromomethyl-4-hydroxymethyl-1,3-dioxolane, which was treated with lithium iodide in 2-butanone to afford the pentadeuterated domiodol 1 in high isotopic purity. Key Words Domiodol, mucolytic drug, deuterium, synthesisFor ongoing projects to study the absorption, distribution, and excretion of the mucolytic drug domiodol (2-iodomethyl-4-hydroxymethyl-l,3-dioxolane, 1)' by gas chromatography-mass spectrometry, we needed a sample of the deuterated iododerivative 2. 2Glycerol-ds with 99% isotopic purity was commercially available (MSD isotopes, Gemany) and the synthesis of the deuterated iodo compound 2 had to be modelled on this starting labelled material.The method reported on the preparation of domiodol 1 heating at high temperatures a mixture of glycerol and iodine could not be used, since a mixture of about twenty iodinated compounds was formed? A more convenient synthesis of unlabelled domiodol 1 started from 1-benzyl glycerol 3, which reacted with bromoacetaldehyde dimethyl acetal to afford bromoderivative 41, in turn